Subject: 8 Tech
------------------------------
Subject: 8.1 Technical Support Numbers
From: Joshua Putnam <Joshua_Putnam@happy-man.com>
[This list is now in the ftp archives as it is too long to put here]
------------------------------
Subject: 8.2 Ball Bearing Grades
From: Bill Codding <peda@simplicity.Stanford.EDU>,
Harry Phinney <harry@hpcvlx.cv.hp.com>
Following is a description of the different grades of ball bearings.
The grade specifies the sphericity of the balls in millionths of an
inch.
Thus, grade 25 are round to 25/10^6, while grade 1000 are good to 1/1000
(i.e. not all that round, but probably good enough for our uses).
Grade 25: the highest quality normally available, aka
"Campagnolo quality": hardened all the
way through, best
alloys, coatings, roundness, and durability.
Evidently,
a recent bottom-bracket overhaul article
in "Bicycling Plus
Mountain Bike" magazine recommended
these. Campy's tech reps
claim that the bearings in a set (usually
in a little paper bag)
are matched. One should not mix
bearings from different sets.
Grade 200: mid-range
Grade 1000: seems to be the lowest, may only be surface
hardened.
Good sources for ball bearings:
Your local bike shop (make sure you're getting the grade
you want)
Bike Parts Pacific
Bike Nashbar 1-800-NASHBAR ($1-$3
per 100 Grade 25)
The Third Hand 1-916-926-2600 ($4-$7 per 100 Grade
25)
------------------------------
Subject: 8.3 SIS Cable Info
From: Jobst Brandt <jbrandt@hpl.hp.com>
After Joe Gorin described the SIS "non-compressive" cable housing to
me I got myself a sample to understand what the difference is.
I
believe "non-compressive" is a misnomer. This cable housing is
NOT
non-compressive but rather a constant length housing. As far
as I can
determine, and from reports from bike shops, this housing should not
be used for brakes because it is relatively weak in compression, the
principal stress for brake housing.
SIS housing is made of 18 strands of 0.5mm diameter round spring steel
wire wrapped in a 100mm period helix around a 2.5mm plastic tube.
The
assembly is held together by a 5mm OD plastic housing to make a
relatively stiff cable housing. Because the structural wires
lie in a
helix, the housing length remains constant when bent in a curve.
Each
strand of the housing lies both on the inside and outside of the curve
so on the average the wire path length remains constant, as does the
housing centerline where the control cable resides. Hence, no
length
change. A brake cable housing, in contrast, changes length with
curvature because only the inside of the curve remains at constant
length while the outside (and centerline) expands.
Shimano recommends this cable only for shift control but makes no
special effort to warn against the danger of its use for brakes.
It
should not be used for anything other than shift cables because SIS
housing cannot safely withstand compression. Its wires stand
on end
and have no compressive strength without the stiff plastic housing
that holds them together. They aren't even curved wires, so they
splay out when the outer shield is removed. Under continuous
high
load of braking, the plastic outer housing can burst leaving no
support. Besides, in its current design it is only half as flexible
as brake cable because its outer shell is made of structurally stiff
plastic unlike the brake cable housing that uses a soft vinyl coating.
Because brake cables transmit force rather than position, SIS cable,
even if safe, would have no benefit. In contrast, with handlebar
controls to give precise shift positioning, SIS housing can offer some
advantage since the cable must move though steering angles. SIS
housing has no benefit for downtube attached shifters because the
cable bends do not change.
------------------------------
Subject: 8.4 Milk Jug Mud Flaps
From: Chuck Tryon <bilbo@bisco.kodak.com>
Actually, I have used plastic like this (or in my case, some
red plastic from a cheap note book cover -- it's heavier) to
extend the
bottom (rear) end of the front fender. The Zephals are
good, but they
don't stop the splash from where the tire hits the road from
getting on my
feet. What I did was cut a small triangle about 3in (~7cm)
wide by 6in
(~15cm) long, cut a hole in the top of it and the bottom end
of the fender,
and use a pop-rivet (with washers to prevent tear out) to attach
it. On a
road bike, it should be end up being within a few inches of
the road. ATB's
will need more clearance, so this won't work well off road.
| |
| |
/| o |\ <-----
rivet with washer on inside
| \___/ |
/
\ <---- flap fits inside of the fender, and follows the
|
| curve, which gives it some
stiffness.
|
|
|
|
\_________/
| |
| |
<----- bottom of tire
\_/
------------------------------
Subject: 8.5 Lubricating Chains
Lubricating chains is a somewhat religious issue. Some advocate
oil,
some Teflon-base lubricants, some paraffin wax. The net majority
favors
a lubricant that does not leave an oily coating on the chain that can
attract dirt, which will hasten chain/chainring/freewheel sprocket
wear.
If you want to use paraffin wax, make sure you melt the wax in a double
boiler! Failure to do so can lead to a fire. You can use
a coffee
can in a pan of boiling water if you don't want to mess up good cookware.
After the wax has melted, put the chain in the wax and simmer for 10
minutes or so. Remove the chain, hang it up, and wipe the excess
wax
off. Let it cool and reinstall on your bike.
When using a liquid lubricant, you want to get the lube onto the pins
inside the rollers on the chains, not on the outside where it does
little
good. Oilers with the narrow tubes are good for this because
you can put
the lube where you want it. Work the oil into the chain after
applying
it, wipe the chain off, and reinstall on your bike.
A good discussion of chain maintenance is at
http://www.sheldonbrown.com/chains.html
------------------------------
Subject: 8.6 Wear and Gear Slippage
From: Jobst Brandt <jbrandt@hpl.hp.com>
Chain wear and care seems to be a never ending discussion, especially
for new bicyclists who are not entirely happy with this dirtiest of
bicycle parts. This leads to the first problem, of whether there
is a
best (and cleanest) way to care for a chain. There are several
ways
to take care of a chain of which some traditional methods are the most
damaging to the chain and others work to prolong life.
At the outset the term "chain stretch" is misleading and wrong.
Chains do not stretch, in the dictionary sense, by elongating the
metal through tension. They lengthen because their hinge pins
and
sleeves wear. This wear is caused almost exclusively by road
grit
that enters the chain when it is oiled. Grit sticks to the outside
of
a chain in the ugly black stuff that can get on ones leg, but external
grime has little functional effect because it is on the outside where
it does the chain no damage. Only when a dirty chain is oiled,
or has
excessive oil on it, can this grit move inside where it causes damage.
Commercial abrasive grinding paste is made of oil and silicon dioxide
(sand) and silicon carbide (sand). You couldn't do a better job
if
you tried to destroy a chain, than to oil a dirty chain.
Primitive rule #1: Never oil a chain on the bike.
This means the chain should be cleaned of grit before oiling it and
because this is practically impossible without submerging the chain
in
a solvent bath (kerosene or commercial solvent), it must be taken off
the bicycle. Devices with rotating brushes, that can be clamped
on
the chain on the bicycle, do a fair job but are messy and do not
prevent fine grit from becoming suspended in the solvent. External
brushing or wiping moves grit out of sight, but mainly into the
openings in the chain where subsequent oiling will carry it inside.
Do not use gasoline because it is explosive and contains toxic light
petroleum fractions that penetrate the skin. Removing the chain
from
the bicycle isn't always possible. There are times (after riding
in
the rain) when a chain screams for oil and a good cleaning is not
practical. In that case rule #1 may be violated for humanitarian
reasons. However, only an internally clean chain squeaks, so
it isn't
as bad as it sounds. Also, water is a moderately good lubricant,
but
as soon as the rain stops, it evaporates.
Removing the solvent from the chain after rinsing is important.
Compressed air is not readily available in the household nor is a
centrifuge. Manually slinging the chain around outdoors works
best if
the chain is a closed loop but without pressing the pin completely
in.
The other way is to evaporate it. Accelerated drying methods
by
heating should be avoided, because they can be explosive.
Lubricating the chain with hot 90W gear lube works but it is also
efficient fly paper, collecting plenty of hardpack between sprockets
and on the outside of the chain. Motor oil is far better, but
motorcycle chain and chainsaw lubricants are better yet, because they
have volatile solvents that allow good penetration for their
relatively viscous lubricant. Paraffin (canning wax), although
clean,
works poorly because it is not mobile and cannot replenish the bearing
surfaces once it has been displaced. This becomes apparent with
any
water that gets on the chain. It immediately sqeaks.
Swaged bushing chains
Sedis was the first with its Sedisport chain to introduce swaged
bushings, formed into the side plates, to replace full width steel
bushings on which the rollers and pins bear. Although stronger
and
lighter than prior chains, it achieves its light weight at the expense
of durability. These chains, now the only derailleur chains
available, have only vestigial sleeves in the form of short collars
on
the side plates to support the roller on the outside and the link pin
on the inside. This design is both lighter and stronger because the
side plates need not have the large hole for insertion of sleeves.
Because MTB's use drive sprockets as small as 18t that can cause
extremely high chain loads, pin and sleeve chains could be at a
disadvantage to safely withstand such loads while shifting.
The pins inside full bushing chains were well protected against
lubricant depletion because both ends were covered by closely fitting
side plates. Some motorcycle chains have O-ring seals at each
end.
In the swaged bushing design there is no continuous tube because the
side plates are formed to support the roller and pin on a collar with
a substantial central gap. In the wet, lubricant is quickly washed
out of pin and roller and the smaller bearing area of the swaged
bushing for the pin and roller easily gall and bind when lubrication
fails. Although this is not a problem for this type of chain
when dry
it has feet of clay in the wet.
Chain Life
Chain life is almost entirely a cleanliness and lubrication question
rather than a load problem. For bicycles the effect of load
variations is insignificant compared to the lubricant and grit
effects. For example, motorcycle primary chains, operated under
oil
in clean conditions, last years while the exposed rear chains must
be
replaced often.
The best way to determine whether a chain is worn is by measuring its
length. A new chain has a half inch pitch with a pin at exactly
every
half inch. As the pins and sleeves wear, this spacing increases
and
this concentrates more load on the last tooth of engagement, changing
the tooth profile. When the chain pitch grows over one half percent,
it is time for a new chain. At one percent, sprocket wear progresses
rapidly because this length change occurs only between pin and sleeve
so that it is concentrated on every second pitch; the pitch of the
inner link containing the rollers remaining constant. By holding
a
ruler along the chain on the bicycle, align an inch mark with a pin
and see how far off the mark the pin is at twelve inches. An
eighth
of an inch (0.125) is a little over the one percent limit while more
than a sixteenth is a prudent time to get a new chain.
Skipping Chain
Sprockets do not change pitch when they wear, only their tooth form
changes. The number of teeth and base circle remain unchanged
by
normal sprocket wear.
A new chain often will not freely engage a worn rear sprocket under
load, even though it has the same pitch as the chain. This occurs
because the previous (worn and elongated) chain formed pockets in the
teeth by exiting under load. A chain with correct pitch cannot
enter
the pockets when its previous roller bears the previous tooth, because
the pocket has an overhang that prevents entry.
Without a strong chain tensioner or a non derailleur bicycle, the
chain has insufficient force on its slack run to engage a driven
sprocket. In contrast, engagement of a driving sprocket, the
crank
sprocket, generally succeeds even with substantial tooth wear, because
the drive tension forces engagement.
However, worn teeth on a driving sprocket cause "chainsuck", the
failure of the chain to disengage the chainwheel. This occurs
more
easily with a long arm derailleur, common to most MTB's, that is one
reason this occurs less with road racing bicycles, that experience
a
noisy disengagement instead.
In contrast a worn chain will not run on a new driving sprocket.
This
is less apparent because new chainwheels are not often used with an
old chain. In contrast to a driven sprocket (rear) the chain
enters
the driving sprocket under tension, where the previous chain links
pull it into engagement. However, because a used chain has a
longer
pitch than the sprocket, previous rollers bear almost no load and
allow the incoming chain link to climb the ramp of the tooth, each
successive link riding higher than the previous until the chain jumps.
The pockets in a used sprocket are small but they change the pressure
angle of the teeth enough to overcoming this problem.
Jobst Brandt <jbrandt@hpl.hp.com>
------------------------------
Subject: 8.7 Adjusting Chain Length
From: Bob Fishell <spike@cbnewsd.att.com>
For all Shimano SIS and Hyperglide systems, the chain is sized by shifting
to
the smallest rear cog and the largest front sprocket, then sizing the
chain so that the derailleur pulleys are on a vertical line, or as
close
as you can get to it. Note that this will result in the same
chain length
for any freewheel within the capacity of the derailleur, so it usually
is
not necessary to re-size the chain for a different cogset with these
systems.
The other rule I've used (friction systems) involves shifting to the
largest
chainring and the largest rear cog, then sizing the chain so that the
pulleys
are at a 45 degree angle to the ground.
The rules probably vary from derailleur to derailleur. In general,
you may use the capacity of the rear derailleur cage as a guideline.
You
want the chain short enough so the cage can take up the slack in the
smallest combination of chainwheel and rear cog you will use. The chain
must also be long enough so that the cage still has some travel in
the
largest combination you will use.
For example, if you have a 42x52 crank and a 13x21 freewheel, the smallest
combination you would use would be a 42/14 (assuming you don't use
the
diagonal). If the cage can take up the slack in this combo, it's short
enough.
If the cage has spring left when you are in the 52/19 combo (again,
you are
not using the diagonal), it's long enough.
------------------------------
Subject: 8.8 Hyperglide chains
For those of you that are tired of dealing with Shimano's
chains with the special pins, I've found that the following
chains work well with Shimano Hyperglide gearing systems:
DID SuperShift
Sedis ATB
Union 800
Union 915
The SuperShift is probably the best performer of the bunch,
followed by the ATB and 915. The 800 doesn't do too well
with narrow cogsets (i.e., 8-speeds) because the raised
elliptical bumps on the side-plates tend to rub on the adjacent
cogs.
I've also found that these chains work well on SunTour systems.
The 915, however, works better on PowerFlo cogs than it does
on regular (AccuShift) cogs (where it tends to slip when shifting).
------------------------------
Subject: 8.9 Bottom Bracket Info
From: Jobst Brandt <jbrandt@hpl.hp.com>
The four kinds of BB threads in common use today are Italian, British,
French, and Swiss, possibly in that order of occurrence.
Diameter
Pitch Right Left Cup
--------
----- ----- -----
Italian 36mm x 24F tpi
right right tpi (threads per
inch)
British 1.370" x 24F tpi left
right
French 35mm x 1mm
right right
Swiss 35mm x
1mm left right
Unless there is something wrong with the right hand cup it should not
be
removed but should be wiped clean and greased from the left side.
The
thread type is usually marked on the face of both left and right cups.
Swiss threads are rare but if you have one it is good to know before
attempting removal.
------------------------------
Subject: 8.10 Crank noises
From: Phil Etheridge <phil@massey.ac.nz>
I've had the creaky crank problem on every bike I've owned which has
had cotterless cranks. Until now, I've never known a good solution
to
the problem.
One suggestion I had was to replace the crank, but that wasn't
something I was prepared to do on 1 month old bike under warranty.
The shop mechanic spent half an hour with me and my bike sorting it
out. Tightening the crank bolts and pedal spindle (i.e. onto
the
crank) didn't help (as Jobst will tell you).
Removing each crank, smearing the spindle with grease and replacing
the crank eliminated most of the noise. Removing each pedal,
smearing
grease on the thread and replacing it got rid of the rest of the
noise.
Greasing the pedal threads is a new one on me, but it makes a lot of
sense, since they are steel and the crank aluminum. I thought
it was
worth relating this story, as creaky cranks seems to be quite a common
problem.
------------------------------
Subject: 8.11 Cracking/Breaking Cranks
From: Jobst Brandt <jbrandt@hpl.hp.com>
Since the advent of the crank cottage industry, crank failures have
become more common than previously because most of these "home made"
cranks, usually produced in prototype quantities on numerically
controlled (NC) milling machines, have not been designed with sound
engineering practices, nor have they been tested destructively in
repeatable tests on testing machines. My comments are mostly
aimed at
major brand production cranks.
Cranks break primarily because they are aluminum and because they have
high stress principally at two places. Aluminum has no distinct
fatigue threshold in contrast to steel, so that with increasing use
and load cranks are destined to break at the two most failure prone
places, the pedal eye, and the junction of the spider fingers and the
right crank.
The pedal eye is weak because the joint is incorrectly designed, but
being standard, it may not be changed since it appears to work.
This
joint always moves under load and through its fretting causes an
undercut in the face of the crank. Removal of a pedal, that has
been
ridden any considerable amount, will reveal a recess in the face of
the crank with cracks around its circumference caused by fretting.
The cracks often propagate into the crank and cause failure.
A
solution to this problem would be a 45 degree taper in place of the
flat shoulder at the end of the pedal thread.
The thin web between the crank and the adjacent legs of a five legged
spider is also a place where most cranks crack. The Campagnolo
C-Record as well as Ritchey cranks address this problem by using the
crank itself as the fifth leg of the spider, and transmitting pedal
torque directly from the crank to the chainwheels. By this
arrangement the spider merely supports the chainwheels radially and
laterally and the driving torque is delivered by a solid anchor.
------------------------------
Subject: 8.12 Biopace chainrings
Biopace chainrings have fallen into disfavor in recent years.
They
are hard to "pedal in circles". The early Biopace chainrings
were
designed for cadences of around 50-70 rpm, while most recommend a
cadence of 80-100 rpm. Newer Biopace chainrings are less elliptical,
but the general consensus is to (if you are buying a new bike) get
the
dealer to change the chainrings to round ones.
Sheldon Brown has some information on Biopage chainrings at
http://www.sheldonbrown.com/biz/hub/biopace.html.
------------------------------
Subject: 8.13 Snakebite flats
Snakebite flats are usually caused by the tire and tube being pinched
between the road and the rim, causing two small holes in the tube that
look like a snakebite. The usual causes are underinflation, too
narrow a tire for your weight, or hitting something (rock, pothole)
while having your full weight on the tire.
The obvious solutions are to make sure your tires are inflated properly,
use a larger size tire if you weigh a lot, and either avoid rocks and
potholes or stand up with your knees and elbows flexed (to act like
shock
absorbers) when you go over them.
------------------------------
Subject: 8.14 Blown Tubes
From: Tom Reingold <tr@samadams.princeton.edu>
Charles E Newman writes:
$ Something really weird happened
at 12:11 AM. My bike blew a
$ tire while just sitting parked in my room. I was awakened by a noise
$ that scared the livin ^&$% out of me. I ran in and found that
all the
$ air was rushing out of my tire. How could something like happen in
the
$ middle of the night when the bike isn't even being ridden? I
have
$ heard of it happening when the bike is being ridden but not when
it is
$ parked.
This happened because a bit of your inner tube was pinched between your
tire bead and your rim. Sometimes it takes a while for the inner
tube
to creap out from under the tire. Once it does that, it has nothing
to
keep the air pressure in, so it blows out. Yes, it's scary.
I've had
it happen in the room where I was sleeping.
To prevent this, inflate the tire to about 20 psi and move the tire
left and right, making sure no part of the inner tube is pinched.
------------------------------
Subject: 8.15 Mounting Tires
From: Douglas Gurr <dgurr@daimi.aau.dk>
A request comes in for tyre mounting tricks. I suspect that this ought
to be
part of the FAQ list. However in lieu of this, I offer the way it was
taught
to me. Apologies to those for whom this is old hat, and also for the
paucity
of my verbal explanations. Pictures would help but, as always, the
best bet
is to find someone to show you.
First of all, the easy bit:
1) Remove the outer tyre bead from the rim. Leave the inner bead.
Handy hint. If after placing the first tyre lever you
are unable to fit another in because the tension in the
bead is too great
then relax the first, slip the second in and use both
together.
2) Pull out the tube finishing at the valve.
3) Inspect the tube, find the puncture and repair it.
Now an important bit:
4) Check tyre for thorns, bits of glass etc - especially at the point
where
the hole in the tube was found.
and now a clever bit:
5) Inflate the tube a _minimal_ amount, i.e. just sufficient for it
to
hold its shape. Too much inflation and it won't fit inside
the tyre.
Too little (including none at all) and you are likely
to pinch it.
More important bits:
6) Fit the tube back inside the tyre. Many people like to cover the
tube in
copious quantities of talcum powder first. This helps
to lubricate
the tyre/tube interface as is of particular importance
in high pressure
tyres.
7) Seat the tyre and tube over the centre of the rim.
8) Begin replacing the outer bead by hand. Start about 90 degrees away
from
the valve and work towards it. After you have safely passed
the valve,
shove it into the tyre (away from the rim) to ensure that
you have
not trapped the tube around the valve beneath the tyre
wall.
Finally the _really_ clever bit:
9) When you reach the point at which you can no longer proceed by hand,
slightly _deflate_ the tube and try again. Repeat this
process until
either the tyre is completely on (in which case congratulations)
or the tube is completely deflated. In the latter case,
you will have
to resort to using tyre levers and your mileage may vary.
Take care.
and the last important check:
10) Go round the entire wheel, pinching the tyre in with your fingers
to check that there is no tube trapped beneath the
rim. If you
have trapped the tube, deduct ten marks and go back
to step one.
Otherwise ....
11) Replace wheel and reinflate.
------------------------------
Subject: 8.16 More Flats on Rear Tires
From: Jobst Brandt <jbrandt@hpl.hp.com>
Date: Thu, 22 Jan 1998 18:15:42 PST
Many sharp objects, especially those that lie flat on the road like
nails and pieces of metal, more often enter rear tires than the front
tires. That is because the front tire upends them just in time
for
the rear tire to be impaled on them.
For example, nails seldom enter front tires. When dropped from
a
moving vehicle, nails slide down the road, and align themselves
pointing toward traffic, because they prefer to slide head first as
they would when laid on a slope. The front tire rolling over
such a
lengthwise nail, can tilt it up just in time for the rear tire to
encounter it on end. I once got a flat from a one inch diameter
steel
washer that the front tire had flipped up so that the rear tire struck
it on edge. When following another wheel closely, the front tire
can
get the "rear tire" treatment from the preceding wheel.
The front wheel set-up effect is especially true for "Michelin" wires,
the fine strands of stainless wire that make up steel belts of auto
tires. These wires, left on the road when such tires exposes
their
belt, cause hard to find slow leaks almost exclusively in rear tires.
When wet, glass can stick to the tire even in the flat orientation and
thereby get a second chance when it comes around again. To make
things worse, glass cuts far more easily when wet as those who have
cut rubber tubing in chemistry class may remember. A wet razor
blade
cuts latex rubber tubing in a single slice while a dry blade only
makes a nick.
As for pinch flats, aka snake bites, they occur on the rear wheel more
readily because it carries more load and is uncushioned when the rider
is seated. The rider's arms, even when leaning heavily on the
front
wheel, cushion impact when striking a blunt obstacle.
------------------------------
Subject: 8.17 What holds the rim off the ground?
From: Jobst Brandt <jbrandt@hpl.hp.com>
> What forces keep the rim of a wheel with pneumatic tires off the
> ground. It obviously can't be the air pressure because that's acting
> from top as well as from below.
As has been pointed out, the casing walls pull on the rim (or its
equivalent) and thereby support the load. The casing leaves the
rim
at about a 45 degree angle, and being essentially a circular cross
section, it is in contact with the rim over its inner quarter circle.
At least this is a good representative model. The visualization
may
be simpler if a tubular tire is considered. It makes no difference
whether the tire is held on by glue or is otherwise attaches to the
rim such as a clincher is. Either way the tire is attached to
the
rim, a relatively rigid structure.
Under load, in the ground contact zone, the tire bulges so that two
effects reduce the downward pull (increase the net upward force) of
the casing. First, the most obvious one is that the casing pulls
more
to the sides than downward (than it did in its unloaded condition);
the second is that the side wall tension is reduced. The reduction
arises from the relationship that unit casing tension is equivalent
to
inflation pressure times the radius of curvature divided by pi.
As
the curvature reduces when the tire bulges out, the casing tension
decreases correspondingly. The inflated tire supports the rim
primarily by these two effects.
Tire pressure changes imperceptibly when the tire is loaded because
the volume does not change appreciably. Besides, the volume change
is
insignificant in small in comparison to the volume change the air has
undergone when being compressed into the tire. In that respect,
it
takes several strokes of a frame pump to increase the pressure of a
tire from 100 psi to 101. The air has a low spring constant that
acts
like a long soft spring that has been preloaded over a long stroke.
Small deflections do not change its force materially. For convenience
car and truck tires are regularly inflated to their proper pressure
before being mounted on the vehicle.
------------------------------
Subject: 8.18 Anodized vs. Non-anodized Rims
From: Jobst Brandt <jbrandt@hpl.hp.com>
Date: Mon, 20 Apr 1998 15:31:32 PDT
Dark anodized rims were introduced a few years ago as a fashionable
alternative to shiny metal finish, possibly as a response to non
metallic composites. Some of these rims were touted as HARD anodized
implying greater strength. Hard anodizing of aluminum, in contrast
to
cosmetic anodizing, produces a porous ceramic oxide that forms in the
surface of the metal, as much as 1/1000 inch thick, about half below
the original surface and half above. It is not thick enough to
affect
the strength of the rim but because it is so rigid, acts like a thin
coat of paint on a rubber band. The paint will crack as the rubber
stretches before any load is carried by the rubber. Similarly,
anodizing cracks before the aluminum carries any significant load.
Rims are made from long straight extrusions that are rolled into
helical hoops from which they are cut to length. Rims are often
drilled and anodized before being rolled into a hoop and therefore,
the anodizing is already crazed when the rim is made. Micro-cracks
in
thick (hard) anodizing can propagate into the metal as a wheel is
loaded with every revolution to cause whole sections of the rim to
break out at its spoke sockets. In some rims, whole sidewalls
have
separated through the hollow chamber so that the spokes remained
attached to the inner hoop and the tire on the outer one. In
contrast, colored anodizing is generally too thin to initiate cracks.
As an example, Mavic MA-2 rims have rarely cracked except on tandems,
while the identical MA-40 rims, with a relativley thin anodizing, have
cracked often.
Anodizing is also a thermal and electrical insulator. Because
heat is
generated in the brake pads and not the rim, braking energy must flow
into the rim to be dissipated to the atmosphere. Anodizing, although
relatively thin, impedes this heat transfer and reduces braking
efficiency by raising the surface temperature of the brakes.
When
braking in wet conditions, road grit wears off anodizing on the
sidewall, an effect that improves braking.
Anodizing is not heat treatment and has no effect on the structural
properties of the aluminum.
------------------------------
Subject: 8.19 Reusing Spokes
From: Jobst Brandt <jbrandt@hpl.hp.com>
>I just bent my wheel and am probably going to need a new one
>built. Can I reuse my old, 3 months, spokes in the new wheel.
>The guy at the shop gave me some mumbo jumbo about tensioning or
>something.
There is no reason why you should not reuse the spokes of your
relatively new wheel. The reason a bike shop would not choose
to do
this is that they do not know the history of your spokes and do not
want to risk their work on unknown materials. If you are satisfied
that the spokes are good quality you should definitely use them for
you new wheel. The spokes should, however, not be removed from
the
hub because they have all taken a set peculiar to their location, be
that inside or outside spokes. The elbows of outside spokes,
for
instance, have an acute angle while the inside spokes are obtuse.
There are a few restrictions to this method, such as that new rim
must have the same effective diameter as the old, or the spokes will
be the wrong length. The rim should also be the same "handedness"
so that the rim holes are offset in the correct direction. This
is
not a fatal problem because you can advance the rim one hole so that
there is a match. The only problem is that the stem will not
fall
between parallel spokes as it should for pumping convenience.
Take a cotton swab and dab a little oil in each spoke socket of the
new rim before you begin. Hold the rims side by side so that
the
stem holes are aligned and note whether the rim holes are staggered
in the same way. If not line the rim up so they are. Then
unscrew
one spoke at a time, put a wipe of oil on the threads and engage it
in the new rim. When they are all in the new rim you proceed
as you
would truing any wheel. Details of this are in a good book on
building wheels.
The reason you can reuse spokes is that their failure mode is
fatigue. There is no other way of causing a fatigue failure than
to
ride many thousand miles (if your wheel is properly built). A
crash
does not induce fatigue nor does it even raise tension in spokes
unless you get a pedal between them. Unless a spoke has a kink
that
cannot be straightened by hand, they can all be reused.
------------------------------
Subject: 8.20 Clinchers vs. Tubulars
From: F.J. Brown <F.Brown@massey.ac.nz>
D.H.Davis@gdt.bath.ac.uk gave some useful hints on mounting clinchers,
mostly involving the use of copious quantities of baby powder, and
trying to convince me that clinchers aren't difficult to mount, so
ease of
mounting isn't a valid reason for preferring tubulars.
wernerj@lafcol.lafayette.edu wrote that although average tubulars ride
'nicer' than average clinchers, there are some clinchers around that
ride
just as 'nice'. He also said that ease of change isn't
a good reason for
preferring tubulars as if you flat in a race, you're either going to
swap
a wheel or drop out. He pointed out that tubulars end up
costing $20 -
$80 per flat.
ershc@cunyvm.cuny.edu gave some of the historic reasons that tubulars
were
preferred: higher pressures, lower weight, stronger, lighter rims.
Said
that only a few of these still hold true (rim strength/weight, total
weight),
but he still prefers the 'feel' of tubulars.
leka@uhifa.ifa.hawaii.edu started this thread with his observations
on
clinchers seperated from their rims in the aftermath of a race crash.
stek@alcvax.pfc.mit.edu comments on improperly-glued tubulars posing
a threat
to other racers by rolling off, and noted that this couldn't happen
with
clinchers.
jbrandt@hpl.hp.com agreed with stek, with the additional note that
it is inadequate inflation that often allows tubulars to roll.
Kevin at Buffalo agreed with stek and jobst about tubulars (improperly
or
freshly glued) sometimes rolling.
ruhtra@turing.toronto.edu says he uses clinchers for cost and convenience.
Clinchers let him carry around a tiny patch kit and some tyre irons,
costing
60c, whereas tubulars would require him to carry a whole tyre, and
would
cost more.
CONCLUSIONS: THE CLINCHER VS. TUBULAR WAR
Tubulars - used to be capable of taking higher pressures, had lower
weight
and mounted
onto stronger, lighter rims than clinchers. Clinchers
have now
largely caught up, but many cyclists thinking hasn't.
Tubular
tyre + rim combination still lighter and stronger.
- are easier to change
than clinchers. This matters more to some
people
than others - triathletes, mechanical morons and those
riding
in unsupported races.
- cost megabucks if
you replace them every time you puncture.
***However***
(and none of the North Americans mentioned this)
down here
in Kiwiland, we ***always*** repair our punctured
tubulars
(unless the casing is cut to ribbons). The process
doesn't
take much imagination, you just unstitch the case, repair
the tube
in the normal manner using the thinnest patches you can
buy, stitch
it back up again and (the secret to success) put a
drop of
Superglue over the hole in the tread.
- can roll off if
improperly glued or inflated. In this case, you
probably
deserve what you get. Unfortunately, the riders behind
you don't.
Clinchers - can be difficult to change (for mechanical morons) and are
always
slower to change than tubulars. Most people still carry a spare
tube and do their repairs when they get home.
- are cheaper
to run: if you puncture a lot clinchers will probably
still save you money over tubulars, even if you repair your
tubulars whenever possible. Tubulars are only repairable most
of the time, you virtually never write off a clincher casing due
to a puncture.
- have improved
immensely in recent years; top models now inflate
to high pressures, and are lighter and stronger than they used
to be. Likewise clincher rims. Some debate over
whether
tubulars are still lighter and tubular rims stronger. Probably
depends on quality you select. No doubt that high quality
clinchers/rims stronger, lighter and mor dependable than cheap
tubular/rim combination.
------------------------------
Subject: 8.21 Presta Valve Nuts
From: Jobst Brandt <jbrandt@hpl.hp.com>
Date: Fri, 07 Nov 1997 16:46:59 PST
Jam nuts on Presta valve stems and pumping.
1. The jam nut holds the stem when pumping so that it does not recede
into the rim when pressing the pump head against the tire.
This is
especially useful when the tire is flat (after installing
the
tube). It also keeps the stem from wiggling around
while pumping.
Removing the nut should present no difficulty unless the
threads
have been damaged or the hands are cold. The cold
may present a
problem, but then just opening the valve nut on a Presta
valve
under such conditions is difficult.
2. Breaking off stems with a frame pump comes from incorrect pumping.
The number of new tubes with broken stems lying along
the road
proves that this occurs far too often. To avoid
breaking the stem,
the pump head should be be held in the fist so that the
pumping
force goes from one hand into the other, not from the
pump into the
valve stem. To practice the correct action, hold
the pump head in
one hand with the thumb over the outlet, and pump vigorously
letting out no air. All the force goes from one
hand into the
other. This is essentially what should take place
when inflating a
tire.
It does no good to "get even" with the stupid tube by discarding
it
on the road for all to see. Most riders understand
how to pump a
tire and see this only as evidence of incompetence rather
than a
faulty tube. Besides, this ostentatious behavior
constitutes
littering for which the the fine in California is $1000.
Bike
shops should instruct new bike owners about the use of
the frame
pump. Along with this there should be some tire
patch hints like
don't try to ride a freshly patched tube, carry a spare
tube and
always use the spare after patching the punctured tube.
Of course
this is a whole subject in itself that is also treated
in the FAQ.
------------------------------
Subject: 8.22 Ideal Tire Sizes
From: Jobst Brandt <jbrandt@hpl.hp.com>
> I'm getting a custom frame built and wondered what
> people thought of using 26 inch road wheels. Smaller
> wheels ought to be lighter and stronger.
and goes on to list advantages and disadvantages, most of which are
less
that important in deciding what size to use. What in fact brought
us
the wheel size (700 or 27") that we have is better understood by the
women riders who have a hard time fitting these wheels into their small
bicycle frames. Wheels would be larger than they are if they
would fit
the average riders bike, but they don't. So the compromise size
is what
we are riding today.
> It seems to me that the most obvious reason for using 27"
> wheels is tradition, but I'm not sure the advantages make
> it worth trying to swim upstream. What do you think?
This line of thought is consistent with the "cost be damned" approach
in bicycling today. The big bucks are spent by people who want
the best
or even better than their peers. The more special the better.
Riders
consistently spend nearly twice the money for wheels and get worse
rims
when they choose anodized ones, whether there is merit to this finish
is of no interest. They cost more so they must be better.
How "custom"
can you get than to have wheels no one else on the block has (maybe
25"?).
If enough riders ask for 24", 25" and 26" wheels, manufacturers will
up
the price as their product lines multiply and the total sales remain
constant. Tires and spokes will follow as a whole range of sizes
that
were not previously stocked become part of the inventory. Meanwhile,
bike frames will come in different configurations to take advantage
of
the special wheel sizes. SIzes whose advantages are imperceptibly
small
but are touted by riders who talk of seconds saved in their last club
TT
or while riding to work.
A larger wheel rides better on average roads and always corners better
because it brings a longer contact patch to the road. A longer
contact
averages traction over more pavement and avoids slip outs for lack
of
local traction. Visualize crossing a one inch wide glossy paint
stripe
with a 27" wheel and an 18" wheel when banked over in a wet turn.
I see this subject arise now and then and it reminds me of the concept
of
splitting wreck.bike into several newsgroups. The perpetrators
bring the
matter up for many of the wrong reasons.
Ride bike, don't re-invent what has been discarded.
------------------------------
Subject: 8.23 Indexed Steering
From: Jobst Brandt <jbrandt@hpl.hp.com>
> In the several years I spent working in a pro shop, I have never
> seen a case of "index steering" (yes, we called it that) that was
> _not_ caused by a "brinelled" headset - one with divots in the
> races. I am 99.999 percent certain that that is your problem.
What
> are you going to do if you don't fix it? I suggest that you
fix the
> headset even if you sell the bike, as a damaged headset could be
> grounds for a lawsuit if the buyer crashes.
I disagree on two points. First, because you use the term "Brinell"
that conveys a notion as incorrect as the phrase "my chain stretched
from climbing steep hills" and second, because there is no possibility
of injury or damage from "indexed" steering head bearings.
Damage to head bearings seems to be twofold in this case because
properly adjusted steering, can only get looser from dimples and it
cannot be immobilized by them. Therefore, the head adjustment
was too
tight. However, dimpling is not caused by impact, but rather
by
lubrication failure that occurs while riding straight ahead.
This
occurs more easily with a correctly adjusted bearing than with a loose
one that rattles and clunks. Rattling replenishes lubricant between
balls and races that would otherwise not be present. Off road
bicycles suffer less from this malady than road bicycles because it
occurs primarily on long straight descents where no steering motions
that would replenish lubrication occur.
If you believe it comes from hammering the balls into the races, I
suggest you try to cause some dimples by hammering on the underside
of
the fork crown of a clunker bike of your choice. Those who hammered
cotters on steel cranks will recall no such dimpling on the spindle,
even though it has a far smaller diameter than the head bearing
although the blows were more severe and direct. No dimples were
made.
Ball bearings make metal-to-metal contact only under fretting loads
(microscopic oscillations) while the bearing is not turning.
Any
perceptible steering motion will replenish lubricant from the oily
meniscus surrounding the contact patch. Peering over the bars
at the
front hub while coasting down a road at 20+ mph you will notice the
fork ends vibrating fore and aft. This motion does not arise
at the
fork end, but at the fork crown, as it bends the steer tube.
Both
head bearings rotate in fretting motion crosswise to the normal plane
of rotation, as the steer tube bends. Dimples form in the forward
and
rearward quadrant of both upper and lower bearings from this fretting.
That they also form in the upper bearing shows they are not directly
load related.
Lubrication failure from fretting causes metal to metal contact to
form microscopic welds between balls and races. These welds
repeatedly tear material from the softer of the two causing the
elliptical milky dimples in the races. Were these brinelling
marks
(embossed through force), they would be shiny and smooth. Various
testimonials for the durability of one bearing over another are more
likely caused by the lubricant than the design of the bearing.
The
rigidly mounted ball bearing has survived longer as a head bearing
than it should, considering its poor performance record.
Roller bearings of various designs have been tried, and it appears
that they were the ones that finally made obvious that fore and aft
motion was the culprit all along; a motion that roller bearings were
even poorer at absorbing than balls. This recognition lead to
putting
spherical seats under the rollers. Although this stopped most
of the
dimpling, these bearings did not work well because the cage of needles
tended to shift off center and drag on the housing while the conical
races also shifted causing the bearing to bind.
It appears that a solution was finally found when Shimano bought a
patent from Wilderness Trail Bikes for a ball bearing that combined
the cup and cone ball bearing with the spherical plain bearing.
Today Shimano offers these bearings model called: LX, XT, 600, STX-RC
and Dura Ace. They have a full-complement angular-contact ball
bearing, whose races are sufficiently reentrant to snap permanently
together. They have rubber seals that retain grease for life
of the
bearing that is not exposed to weather. The ball bearing is supported
on a spherical steel ring that forms a plain bearing against the
aluminum housing. The plain bearing takes up the otherwise damaging
out-of-plane motion while the ball bearing does the steering.
The
bearing is only durable as long as the plain bearing remains properly
greased.
------------------------------
Subject: 8.24 Sidepull, Dual Pivot, and the Delta Brakes
From: Jobst Brandt <jbrandt@hpl.hp.com>
Date: Wed, 30 Oct 1996 15:03:28 PST
The bicycle brake has seen many variations since the introduction of
the standard single pivot caliper brake about 100 years ago.
This
brake, commonly called the side pull, has been the mainstay until a
wave of designs began about 30 years ago. Meanwhile the cantilever
brake with large wheel clearance existed only in a limited way until
the advent of the mountain bike. The need for wide clearance
over
large tires favors this brake that pivots from cantilevers on the fork
blades and does not restrict tire clearance. As is often the
case,
these advantages are not gained without drawbacks such as fork braking
forces that spread abd jam suspension forks unless a U-shaped stress
plate is used, and the steep angle of motion that causes the pads to
slip under the rim (total brake failure) with pad wear.
Until recently, most brakes had a hand lever ratio (mechanical
advantage) of 4:1, and a caliper or brake arm linkage with a 1:1
ratio, making most brakes and levers interchangeable. From time
to
time, brakes have been designed to address certain real or perceived
failings of the common caliper rim brake. Most of these had a
novel
linkage that promised a theoretical advantage. One of these,
the
centerpull brake of the 1950's, was the rave for nearly a decade, in
spite of being entirely without merit, being worse in all respects
than the side pull brake with which it competed. Its brief popularity
might indicate a dissatisfaction with the status quo.
Servo brakes, that use brake reaction force to reinforce application
force, have been designed without success. These schemes fail
for the
reason that a small change in the friction coefficient causes a large
change in braking, making control difficult. With self servo,
the
relationship between application force and brake response is non
linear and unpredictable. To escape this self servo effect in
drum
brakes, automobiles and motorcycles switched to disk brakes, where
the
brake application pressure is at right angles to the braking force.
It is curious that bicycles should try to switch the other way.
For lack of a power source such as cars have, other mechanisms with
variable ratios have been designed for bicycles, one of which was
recently turned into a major blunder for Campagnolo. Campagnolo
introduced the Delta brake (aka Modolo Chronos), whose mechanism is
an
equilateral parallelogram with the cable drawing two opposite corners
of a "diamond" together such that the other two corners expand.
The
motion can be visualized by placing the tips of the thumbs and
forefingers together to form a diamond, palms nearly together.
Moving
the tips of the diamond together at a constant rate demonstrates the
progressive nature of the mechanism and the resulting braking action,
the brake pads being connected by links to the knuckle joints as it
were.
The motion is a tangent function that goes from zero to infinity.
An
example of this is the motion of the top of a ladder, leaning steeply
against a wall, as the foot of the ladder moves away from the wall
at
a constant rate. At first the the top of the ladder moves
imperceptibly, gradually accelerating, until near the bottom its speed
approaches infinity. Although the Delta does not use the extremes
of
this range, it has this characteristic in contrast to a sidepull brake
that has a constant ratio throughout its range.
Although the sidepull brake remains the best performing brake to date,
its major flaw is that the return springs of the single pivot version
make sliding contact with the caliper arms. Because the contact
points are exposed, their friction is uncontrollable and invariably
lead to unequal retraction of the pads so that the brake is usually
off center and tends to drag. To avoid this, the single pivot
sidepull brake requires large pad-to-rim clearance that in turn
prescribes a low overall mechanical advantage of about 4:1 to
accommodate the reach of the human hand.
To offer greater leverage at the same total hand stroke, pad-to-rim
clearance must be reduced, which is only possible if pad position can
be guaranteed. The dual pivot brake achieves this with two pivot
points that define the line of action with two interlinked arms that
are constrained to move equally to remain centered. Precise centering
permits adjusting the pads as close to the rim as wheel trueness
permits. Typically, with minimal free travel, mechanical advantages
of about 5.6:1 are practical.
The higher leverage is not achieved entirely without compromise.
The
offset arm (the one on the right) sweeps its pad upward into the tire
so that this pad must be re adjusted as it wears. The brake cannot
track a crooked wheel that, for instance has a broken spoke.
Because
it has a high ratio, it does not work at all when the quick release
is
accidentally left open, and it changes its hand lever position about
40% faster with pad wear than a single pivot brake.
Part of the light feel of the dual pivot brake arises from the lower
(reverse) ratio of the caliper, whose springs now no longer exert as
strong a return force on the cable and hand lever. Because this
force
is lower, a return spring has been added to the hand lever. The
lower
cable return force coincidentally reduces cable drag during free
motion of the brake (before making contact with the rim). This
makes
the brake feel even more forceful because it has such a light action.
Hydraulic brakes have their own problems that keep them in an almost
invisible presence in general bicycling. Their advocates insist
that
they are superior in all respects in spite of their lack of acceptance
by the bicycling public at large.
------------------------------
Subject: 8.25 Seat adjustments
From: Roger Marquis <marquis@roble.com>
[More up to date copies of Roger's articles can be found at
http://www.roble.com/marquis/]
The following method of setting saddle height
is not the
only method around for setting your saddle height but it is the
most popular among coaches and riders both here and in Europe.
A) Adjust saddle level or very slightly nose
up, no more
than 2mm at the nose.
B) Put on the shoes you normally ride in. Have
wrench ready
(usually a 5mm Allen).
C) Mount the bike and sit comfortably, leaning
against a
wall. Hold a brake on with
one hand (or mount the bike on a
turbo trainer if you have
one).
D) Place your HEELS on the pedals, opposite
the clip, pedal
backwards at 30+ rpm without
rocking your pelvis (very
important).
E) Adjust seat height so that there is about:
E1) ZERO TO ONE HALF CM. for recreational riders (-50 mi/wk.),
E2) ONE HALF TO ONE CM. for experienced riders (50+ mi./wk.),
E3) ONE TO ONE AND ONE HALF CM. for endurance
cyclists (250+
mi./wk.), between
your heel and the pedal. If your soles are
thicker at the cleat
than at the heel adjust accordingly.
Don't forget to grease the seat post.
F) Ride. It may take a couple of rides to get
used to the
feel and possibly stretch
the hamstrings and Achilles
slightly.
Roger Marquis (marquis@roble.com)
------------------------------
Subject: 8.26 Cleat adjustments
From: Roger Marquis <marquis@roble.com>
[note: You may also want to consider going to a bike shop that
does
Fit Kit and have them do the Fit Kit RAD to adjust your cleats.
Many
people recommend it.]
[More up to date copies of Roger's articles can be found at
http://www.roble.com/marquis/]
A) Grease the cleat bolts and lightly tighten.
B) Sitting on the bike, put your feet in the pedals and adjust until:
B1) The ball of your foot is directly
above or, more commonly,
slightly
behind the pedal axle and:
B2) There is approximately 1 cm.
(1/2in.) between your ankle
and the
crank arm.
Note: Cleats that are adjusted too far
forward on the shoe can
cause excessive ankle movement and strain the Achilles
tendon.
C) Tighten the cleat bolts 80% and go out for
a ride. If another
position feels more comfortable
rotate your foot into that
position.
D) Carefully remove your shoes from the pedals
and tighten the
bolts fully. If you cannot
get out of the pedals without
shifting the cleats leave
your shoes on the bike and draw an
outline around the cleat.
Roger Marquis (marquis@roble.com)
------------------------------
Subject: 8.27 SIS Adjustment Procedure
From: Bob Fishell <spike@cbnewsd.att.com>
Shimano's instructions for adjusting SIS drivetrains varies from series
to series. The following method, however, works for each of mine
(600EX,
105, and Deore'). [Ed note: Works on Exage road and mtb
also.]
Your chain and cogs must be in good shape, and the cable must be free
of kinks, slips, and binds. The outer cable should have
a liner.
clean and lubricate all points where the cable contacts anything.
SIS adjustment:
1) Shift the chain onto the largest chainwheel and the smallest cog,
e.g., 52 and 13.
2) WITHOUT TURNING THE CRANKS, move the shift lever back until it
clicks, and LET GO. This is the trick to adjusting
SIS.
3) Turn the crank. If the chain does not move crisply onto the
next
inside cog, shift it back where you started, turn the
SIS barrel
adjuster (on the back of the rear derailleur) one-half
turn CCW,
and go back to step 2. Repeat for each pair of cogs
in turn
until you can downshift through the entire range of the
large
chainwheel gears without the chain hesitating. If
you have just
installed or reinstalled a shift cable, you may need to
do this
several times.
4) Move the chain to the small chainring (middle on a triple) and the
largest cog.
5) turn the cranks and upshift. If the chain does not move crisply
from the first to the second cog, turn the SIS barrel
adjuster
one-quarter turn CW.
If the drivetrain cannot be tuned to noiseless and trouble-free
SIS operation by this method, you may have worn cogs, worn chain,
or a worn, damaged, or obstructed shift cable. Replace as needed
and repeat the adjustment.
------------------------------
Subject: 8.28 Where to buy tools
You can buy tools from many sources. Some tools can be purchased
at
your local hardware store (wrenches, socket sets, etc), while the
special bike tools can be purchased from your local bike store or
one of the mail order stores listed elsewhere.
You can buy every tool you think looks useful, or just buy the tools
you need for a particular repair job. Buying the tools as you
need
them will let you build up a nice tool set over time without having
to drop a lot of money at once.
Some common tools you will need are:
Metric/SAE wrenches for nuts and bolts (or an assortment of adjustable
wrenches).
Screwdrivers, both flat and phillips.
Metric allen wrenches.
Pliers.
Wood or rubber mallet for loosening bolts.
Special tools and their uses:
Cone wrenches to adjust the hub cones.
Chain tool to take the chain apart for cleaning and lubrication,
and
to put it back together.
Tire irons for removing tires.
Spoke wrenches for adjusting spokes.
Cable cutters for cutting cables (don't use diagonal pliers!).
Crankarm tools for removing crankarms.
Bottom bracket tools for adjusting bottom brackets.
Headset wrenches to adjust the large headset nut.
------------------------------
Subject: 8.29 Workstands
There are a variety of workstands available, from about $30 to over
$130. Look at the mail order catalogs for photos showing the
different
types. The type with a clamp that holds one of the tubes on the
bike
are the nicest and easy to use. Park has a couple of models,
and their
clamp is the lever type (pull the lever to lock the clamp). Blackburn
and Performance have the screw type clamp (screw the clamp shut on
the
tube.
If you have a low budget, you can use two pieces of rope hanging from
the ceiling with rubber coated hooks on the end - just hang the bike
by the top tube. This is not as steady as a workstand, but will
do
an adequate job.
------------------------------
Subject: 8.30 Workstands 2
From: Douglas B. Meade <meade@bigcheese.math.scarolina.edu>
>>>>>>>>>> BICYCLE REPAIR STAND SUMMARY <<<<<<<<<<
The Park PRS6 was recommended by several (>5) responders; all
other models were recommended by no more than one responder.
Park PRS6
PROS: full 360\degree rotation
spring-loaded clamp is adjustable
very stable
CONS: not height adjustable
not easy to transport
clamp probably can't work with fat-tubed mtn bike
COST: ~$150
SOURCE: catalogs, local bike shops
Park Consumer
PROS: foldable
convenient
portable
CONS: not as stable as PRS6
COST: ~$100
SOURCE: catalogs, local bike shops
Park BenchMount
PROS: stronger, and more stable, than many floor models
CONS: must have a workbench with room to mount the stand
COST: $???
SOURCE: ???
Blackburn
PROS: The stand folds flat and is portable.
It has a 360 degree rotating clamp.
It is relatively stable.
CONS: crank-down clamp does not seem to be durable
crank bolt is not standard size; difficult to replace
hard to get clamp tight enough for stable use
clamp scratchs paint/finish
problems getting rotating mechanism to work properly
COST: ~$100
SOURCE: catalogs, local bike shops
Performance
PROS:
CONS: not too stable
Ultimate Repair Stand
PROS: excellent quality
includes truing stand
includes carrying bag
CONS:
COST: ~$225
SOURCE: order through local bike shop
the U.S. address for Ultimate Support Systems is :
Ultimate Support Systems
2506 Zurich Dr.
P.O. Box 470
Fort Collins, CO. 80522-4700
Phone (303) 493-4488
I also received three homemade designs. The first is quite simple:
hang the bike from coated
screw hooks
(available in a hardware store for less that $5/pair)
The others are more sophisticated. Here are the descriptions provided
by the designers of the systems.
Dan Dixon <djd@hpfcla.fc.hp.com> describes a modification
of the Yakima Quickstand attachment into a freestanding workstand
I picked up the Yakama clamp
and my local Bike shop for
around $25. What you
get is the clamp and a long carraige
bolt with a big (5") wing
nut. This is meant to be attached
to their floor stand or
their roof racks. The roof rack
attachment is ~$60; expensive,
but great for road trips.
I, instead, bought a longer
carraige bolt, a piece of
3/4" threaded lead pipe,
two floor flanges, and some 2x4's.
(about $10 worth of stuff).
You say you want to attach it to a bench (which should be easy)
pipe
+- clamp |
wing nut
|
| |
V
| +--+ V
| |---------+ V
| | O
| | | |\_________/| |
| /
| | -O- |=| _________ |=| |==I
| | | |/
\| | | \
| |---------+
| | O
| |
/\ /\ | |<-2x4
| | | |
flanges--+---------+ | |
| |
Excuse the artwork, but it
might give you and Idea about
what I mean. You could just
nail the 2x4 to the bench or
something. I really like
the clamp because it is totally
adjustable for different
size tubes.
Eric Schweitzer <ERSHC@cunyvm.cuny.edu> prefers the following
set-up to the Park `Professional' stands that he also has.
My favorite 'stand', one
I used for many years, one that I
would use now if my choice
of stand were mine, is made very
cheaply from old seats and
bicycle chain. Two seats (preferably
cheap plastic shelled seats)
(oh...they must have one wire
bent around at the front
to form the seat rails...most seats
do) have the rails removed
and bent to form 'hooks'. The
'right' kind of hooks are
placed in a good spot on the ceiling
about 5 or 6 feet apart.
(really, a bit longer than the length
of a 'typical' bike from
hub to hub. If you do a lot of tandems
or LWB recombants, try longer
:) Form a loop in one end of the
chain by passing a thin
bolt through the opening between 'outer'
plates in two spots on the
chain. (of course, this forms a loop
in the chain, not the bolt).
The same is done at the other end
to form loops to hold the
seat rail/hooks. First, form the hooks
so they form a pair of Js,
about 2 inch 'hook's The hook for the
front of the bike is padded,
the one for the rear looped through
the chain, squeezed together
to a single hook, and padded.
To use, hook the rear hook
under the seat, or at the seat stays.
Hook the front with each
arm on oposite sides of the stem. Can
also hook to head tube (when
doing forks). Either hook can grab
a rim to hold a wheel in
place while tightening a quick release
skewer or axle bolt. There
is no restricted access to the left
side of the bike. I try
to get the BB of a 'typical' frame about
waist height.
In closing, here is a general statement that only makes my decision
more difficult:
My best advice is to consider
a workstand a long term durable good.
Spend the money for solid
construction. Good stands don't wear or
break, and will always be
good stands until the day you die, at
which point they will be
good stands for your children. Cheese will
always be cheese until it
breaks.
------------------------------
Subject: 8.31 Frame Stiffness
From: Bob Bundy <bobb@ico.isc.com>
As many of you rec.bicycles readers are aware, there have been occasional,
sometimes acrimonious, discussions about how some frames are so much
stiffer than others. Cannondale frames seem to take most of the
abuse.
The litany of complaints about some bike frames is long and includes
excessive wheel hop, numb hands, unpleasant ride, broken spokes,
pitted headsets, etc. I was complaining to a friend of mine about
how there
was so much ranting and raving but so little empirical data - to which
he replied, "Why don't you stop complaining and do the measurements
yourself?". To that, I emitted the fateful words, "Why not, after
all,
how hard can it be?". Following some consultation with Jobst
and a few
other friends, I ran the following tests:
The following data were collected by measuring the vertical deflection
at
the seat (ST), bottom bracket (BB) and head tube (HT) as a result of
applying 80lb of vertical force. The relative contributions of
the
tires, wheels, fork, and frame (the diamond portion) were measured
using
a set of jigs and a dial indicator which was read to the nearest .001
inch. For some of the measures, I applied pressures from 20 to
270 lbs
to check for any significant nonlinearity. None was observed.
The same
set of tires (Continentals) and wheels were used for all measurements.
Note that these were measures of in-plane stiffness, which should be
related to ride comfort, and not tortional stiffness which is something
else entirely.
Bikes:
TA - 1987 Trek Aluminum 1200, this model has a Vitus front fork, most
reviews describe this as being an exceptionally
smooth riding bike
SS - 1988 Specialized Sirus, steel CrMo frame, described by one review
as
being stiff, hard riding and responsive
DR - 1987 DeRosa, SP/SL tubing, classic Italian road bike
RM - 1988 Cannondale aluminum frame with a CrMo fork, some reviewers
could not tolerate the rough ride of
this bike
TA
SS
DR
RM
----------
---------- ----------
----------
ST
BB HT ST BB HT
ST BB HS ST BB HT
diamond 1 1 0
2 2 0 2
2 0 1 1
0
fork 3 11 45
3 9 36 4 13
55 3 10 40
wheels 2 2 2
2 2 2 2
2 2 2 2
2
tires 68 52 66
68 52 66 68 52 66
68 52 66
total 74 66 113
75 65 104 76 69 123
74 65 108
What is going on here? I read the bike mags and this net enough
to know
that people have strong impressions about the things that affect ride
comfort. For example, it is common to hear people talk about
rim types
(aero vs. non-aero), spoke size, butting and spoke patterns and how
they
affect ride. Yet the data presented here indicate, just a Jobst
predicted,
that any variation in these factors will essentially be undetectable
to
the rider. Similarly, one hears the same kind of talk about frames,
namely, that frame material X gives a better ride than frame material
Y, that
butted tubing gives a better ride that non-butted, etc. (I may
have even
made such statements myself at some time.) Yet, again, the data
suggest
that these differences are small and, perhaps, even undetectable.
I offer
two explanations for this variation between the data and subjective
reports
of ride quality.
Engineering:
These data are all static measurements and perhaps only applicable
at the
end of the frequency spectrum. Factors such as frequency response,
and
damping might be significant factors in rider comfort.
Psychology:
There is no doubt that these bikes all look very different, especially
the
Cannondale. They even sound different while riding over rough
roads. These factors, along with the impressions of friends and
reviews
in bike magazines may lead us to perceive differences where they, in
fact,
do not exist.
Being a psychologist, I am naturally inclined toward the psychological
explanation. I just can't see how the diamond part of the frame
contributes
in any significant way to the comfort of a bike. The damping
of the frame
should be irrelevant since it doesn't flex enough that there is any
motion to actually dampen. That the frame would become flexible
at
some important range of the frequency spectrum doesn't seem likely
either.
On the other hand, there is plenty of evidence that people are often
very
poor judges of their physical environment. They often see relationships
where they don't exist and mis-attribute other relationships.
For example,
peoples' judgement of ride quality in automobiles is more related to
the
sounds inside the automobile than the ride itself. The only way
to get
a good correlation between accelerometers attached to the car seat
and
the rider's estimates of ride quality is to blindfold and deafen the
rider (not permanently!). This is only one of many examples of
mis-
attribution. The role of expectation is even more powerful.
(Some even
claim that whole areas of medicine are built around it - but that is
another story entirely.) People hear that Cannondales are
stiff and,
let's face it, they certainly *look* stiff. Add to that the fact
that
Cannondales sound different while going over rough roads and perhaps
the rider has an auditory confirmation of what is already believed
to
be true.
Unless anyone can come up with a better explanation, I will remain
convinced that differences in ride quality among frames are more a
matter of perception than of actual physical differences.
------------------------------
Subject: 8.32 Frame materials
[Ed note: I got this information from some of the books I have.
People
in the know are welcome to update this.]
There are several materials that are used to make bicycle frames.
They
are:
Mild steel - usually used in cheap department store bikes.
Frames
made from mild steel are heavy.
High carbon steel - a higher quality material used in low end
bikes.
Reynolds 500 is an example.
Steel alloy - lighter and better riding than high-carbon frames.
Reynolds
501 and Tange Mangaloy are examples.
Chro-moly - also called chrome-molybdenum or manganese-molybdenum
steel.
One of the finest alloys for bike frames. Reynolds 531 and
Columbus SL and SP are some of the best known brands.
Carbon fiber - high tech stuff. Made from space-age materials,
frames
made of this are very light and strong. Some problems
have been seen in the connections between the tubes and
bottom bracket, etc.
Aluminum - Light frames, usually with larger diameter
tubes.
Cannondale is a well-known brand.
------------------------------
Subject: 8.33 Bike pulls to one side
From: Jobst Brandt <jbrandt@hpl.hp.com>
For less than million dollar bikes this is easy to fix, whether it corrects
the cause or not. If a bike veers to one side when ridden no-hands,
it
can be corrected by bending the forks to the same side as you must
lean
to ride straight. This is done by bending the fork blades one
at a time,
about 3 mm. If more correction is needed, repeat the exercise.
The problem is usually in the forks although it is possible for frame
misalignment to cause this effect. The kind of frame alignment
error
that causes this is a head and seat tube not in the same plane.
This
is not easily measured other than by sighting or on a plane table.
The trouble with forks is that they are more difficult to measure even
though shops will not admit it. It takes good fixturing to align
a
fork because a short fork blade can escape detection by most
measurement methods. Meanwhile lateral and in-line corrections
may
seem to produce a straight fork that still pulls to one side.
However, the crude guy who uses the method I outlined above will make
the bike ride straight without measurement. The only problem
with
this is that the bike may pull to one side when braking because the
fork really isn't straight but is compensated for lateral balance.
This problem has mystified more bike shops because they did not recognize
the problem. Sequentially brazing or welding fork blades often
causes
unequal length blades and bike shops usually don't question this dimension.
However, in your case I assume the bike once rode straight so something
is crooked
------------------------------
Subject: 8.34 Frame repair
From: David Keppel <pardo@cs.washington.edu>
(Disclaimer: my opinions do creep in from time to time!)
When frames fail due to manufacturing defects they are usually
replaced under warranty. When they fail due to accident or abuse
(gee, I don't know *why* it broke when I rode off that last
motorcycle jump, it's never broken when I rode it off it before!)
you are left with a crippled or unridable bike.
There are various kinds of frame damage that can be repaired.
The
major issues are (a) figuring out whether it's repairable (b) who
can do it and (c) whether it's worth doing (sometimes repairs just
aren't worth it).
Kinds of repairs: Bent or cracked frame tubes, failed joints, bent
or missing braze-on brackets, bent derailleur hangars, bent or
broken brake mounts, bent forks, etc. A frame can also be bent
out
of alignment without any visible damage; try sighting from the back
wheel to the front, and if the front wheel hits the ground to one
side of the back wheel's plane (when the front wheel is pointing
straight ahead), then the frame is probably out of alignment.
* Can it be repaired?
Just about any damage to a steel frame can be repaired. Almost
any
damage to an aluminum or carbon fiber frame is impossible to repair.
Titanium frames can be repaired but only by the gods. Some frames
are composites of steel and other materials (e.g., the Raleigh
Technium). Sometimes damage to steel parts cannot be repaired
because repairs would affect the non-steel parts.
Owners of non-steel frames can take heart: non-steel frames can
resist some kinds of damage more effectively than steel frames, and
may thus be less likely to be damaged. Some frames come with
e.g.,
replacable derailleur hangers (whether you can *get* a replacement
is a different issue, though). Also, many non-steel frames have
steel forks and any part of a steel fork can be repaired.
Note: For metal frames, minor dents away from joints can generally
be ignored. Deep gouges, nicks, and cuts in any frame may lead
to
eventual failure. With steel, the failure is generally gradual.
With aluminum the failure is sometimes sudden.
Summary: if it is steel, yes it can be repaired. If it isn't steel,
no, it can't be repaired.
* Who can do it?
Bent derailleur hangers can be straightened. Indexed shifting
systems are far more sensitive to alignment than non-indexed.
Clamp
an adjustable wrench over the bent hanger and yield the hanger
gently. Leave the wheel bolted in place so that the derailleur
hanger
is bent and not the back of the dropout. Go slowly and try not
to
overshoot. The goal is to have the face of the hanger in-plane
with
the bike's plane of symmetry.
Just about any other repair requires the help of a shop that builds
frames since few other shops invest in frame tools. If you can
find
a shop that's been around for a while, though, they may also have
some frame tools.
* Is it worth it?
The price of the repair should be balanced with
* The value of the bicycle
* What happens if you don't do anything about the damage
* What would a new bike cost
* What would a new frame cost
* What would a used bike cost
* What would a used frame cost
* What is the personal attachment
If you are sentimentally attached to a frame, then almost any repair
is worth it. If you are not particularly attached to the frame,
then you should evaluate the condition of the components on the rest
of the bicycle. It may be cheaper to purchase a new or used frame
or even purchase a whole used bike and select the best components
from each. For example, my most recent reconstruction looked
like:
* Bike's estimated value: $300
* Do nothing about damage: unridable
* Cost of new bike: $400
* Cost of new frame: $250+
* Cost of used bike: $200+
* Cost of used frame: N/A
* Cost of repair: $100+
* Personal attachment: zip
Getting the bike on the road again was not a big deal: I have lots
of other bikes, but I *wanted* to have a commuter bike. Since
I
didn't *need* it, though, I could afford to wait a long time for
repairs. The cost of a new bike was more than I cared to spend.
It is hard to get a replacement frame for a low-cost bicycle.
I
did a good bit of shopping around and the lowest-cost new frame
that I could find was $250, save a low-quality frame in the
bargain basement that I didn't want. Used frames were basically
the
same story: people generally only sell frames when they are
high-quality frames. Because the bike was a road bike, I could
have
purchased a used bike fairly cheaply; had the bike been a fat-tire
bike, it would have been difficult to find a replacement. The
cost
of the frame repair included only a quick ``rattlecan'' spray, so
the result was aesthetically unappealing and also more fragile.
For
a commuter bike, though, aesthetics are secondary, so I went with
repair.
There is also a risk that the `fixed' frame will be damaged. I
had
a frame crack when it was straightened. I could have had the
tube
replaced, but at much greater expense. The shop had made a point
that the frame was damaged enough that it might crack during repair
and charged me 1/2. I was able to have the crack repaired and
I
still ride the bike, but could have been left both out the money
and without a ridable frame.
* Summary
Damaged steel frames can always be repaired, but if the damage is
severe, be sure to check your other options. If the bicycle isn't
steel, then it probably can't be repaired.
------------------------------
Subject: 8.35 Frame Fatigue
From: John Unger <junger@rsg1.er.usgs.gov>
I think that some of the confusion (and heat...) on this subject
arises because people misunderstand the term fatigue and equate it
with some sort of "work hardening" phenomena.
By definition, metal fatigue and subsequent fatique failure are
well-studied phenomena that occur when metal (steel, aluminum,
etc.) is subjected to repeated stresses within the _elastic_ range
of its deformation. Elastic deformation is defined as deformation
that results in no permanent change in shape after the stess is
removed. Example: your forks "flexing" as the bike rolls over a
cobblestone street.
(an aside... The big difference
between steel and aluminum
as a material for bicycles
or anything similar is that you
can design the tubes in
a steel frame so that they will
NEVER fail in fatigue. On
the other hand, no matter how
over-designed an aluminum
frame is, it always has some
threshold in fatigue cycles
beyond which it will fail.)
This constant flexing of a steel frame that occurs within the
elastic range of deformation must not be confused with the
permanent deformation that happens when the steel is stressed beyond
its elastic limit, (e. g., a bent fork). Repeated permanent
deformation to steel or to any other metal changes its strength
characteristics markedly (try the old "bend a paper clip back and
forth until it breaks" trick).
Because non-destructive bicycle riding almost always limits the
stresses on a frame to the elastic range of deformation, you don't
have to worry about a steel frame "wearing out" over time.
I'm sorry if all of this is old stuff to the majority of this
newsgroup's readers; I just joined a few months ago.
I can understand why Jobst might be weary about discussing this
subject; I can remember talking about it on rides with him 20 years
ago....
------------------------------
Subject: 8.36 Weight = Speed?
> I was wondering if anyone could help me figure out why heavier
> people roll down hills faster than the little scrawnies like myself.
Surface as well as cross sectional area of an object (a human body)
increases more slowly than its weight (volume). Therefore, wind
drag,
that is largely dependent on surface, is proportionally smaller for
a
heavier and larger object than a smaller one of similar shape and
composition. A good example is dust at a rock quarry that remains
suspended in the air for a long time while the larger pieces such as
sand, gravel, and rock fall increasingly faster to the ground.
They
are all the same material and have similar irregular shapes but have
different weight to surface area ratios, and therefore, different wind
resistance to weight ratios. This applies equally to bicyclists
coasting down hills if other factors such as clothing and position
on
the bicycle are similar.
------------------------------
Subject: 8.37 Adjusting SPD Cleats
Six adjustments can be made when setting up SPD cleats. With the
foot
parallel to the ground and pointing in the direction of travel, the
adjustments are:
1) Left/right translation
2) Front/back translation
3) Up/down translation
4) Front to back tilt
5) Side to side tilt
6) Azimuth, often called "rotation"
Front to back tilt is adjusted as the bicycle is pedaled since the
pedals themselves rotate freely in this direction.
Some people may need to adjust side to side tilt, but this requires
the use of shims which are not provided and can cause the cleat to
protrude beyond the tread of the shoe. Custom insoles that have
one side slightly thicker than the other may have the same effect
as shims between the cleat and the shoe.
Separate up/down adjustments for each leg may be necessary for
individuals with established leg length differences. To adjust
up/down translation in one shoe use a combination of an insole
and raise or lower the seat. To make small up/down changes
equally in both legs, simply raise or lower the seat.
The usual adjustments for SPD cleats are left/right, front/back,
and Azimuth. Of these Azimuth is the most sensitive. For
most
people these three adjustments are sufficient to obtain a
comfortable alignment.
-----------------
Aligning SPD cleats:
Position the cleat so that it lies on the imaginary line between the
bony knob on the inside of your foot at the base of your big toe and
a similar but smaller knob on the outside of the foot at the base of
the smallest toe. Set azimuth so that the pointed end of the
cleat
points directly toward the front of the shoe.
If you're switching from clips and straps, and you are satisfied with
your current alignment, use the following alternate method. Position
your SPD shoe fully in the clip of your old pedal and align the cleat
to the spindle of your old pedal. Center the cleat in the X direction,
leaving room to adjust either way should the need arise.
Some people find pedaling more comfortable if their left and right
feet are closer together. This is sometimes called the "Q-factor".
If you prefer to start with a low Q-factor, then move the cleat so
that
it is as close as possible to the outside of the shoe. Tighten
both
cleat bolts before engaging the pedal.
Adjust the release tension of the pedals so that it is somewhere in
the low to middle part of the tension adjustment range. The higher
the release tension, the harder it will be for you to disengage the
pedals when dismounting. The lower the release tension, the easier
it
will be for you to inadvertently pull out of the pedals, especially
when standing and pedaling. If you stand often to power up hills,
consider setting the initial release tension higher as an unwanted
release under these conditions can result in a painful spill.
See
the pedal instructions.
Mount your bike on a trainer, if you have one, to make preliminary
cleat and release tension adjustments. Practice engaging and
disengaging the pedals a few times before you take a real ride.
Soon you will find this easy. If you notice that a shoe rubs
a
crank or chainstay, adjust left/right translation and azimuth
until the shoe no longer rubs.
As you pedal, you will probably find the initial azimuth
uncomfortable on one or both legs. Notice how your foot would
like
to rotate. Adjust the azimuth of the appropriate cleat in the
same
direction your foot wants to rotate. For example, if your foot
wants to rotate clockwise, adjust the azimuth of the cleat (when
looking at the bottom of the shoe) clockwise. Start by making
moderate corrections. If you overshoot the adjustment, correct
by
half as much.
As you approach optimum azimuth, you may need to ride longer before
you notice discomfort. Take your bike off the trainer, and go
for
a real ride! And bring your 4mm allen key.
You may find very small azimuth adjustments difficult to make.
This
happens because the cleat has made an indentation in the stiff sole
material (usually plastic, sometimes with a tacky, glue-like
material where a portion of the sole was removed). When you tighten
the cleat after making a small correction, it will tend to slide back
into the old indentation. Try moving the cleat one millimeter
or so
to the side or to the front or back, so the cleat can no longer slip
into the old indentation pattern as it is being tightened.
Pain in the ball of your foot can be relieved. One way is by moving
the cleat rearward. Start by moving the cleat about two to three
millimeters closer to the rear of the shoe. Be careful not to
change
the azimuth. When pedaling notice how far your heel is from the
crank. After making a front/rear adjustment, check to make sure
the
crank-heel distance has not noticeably changed.
Moving a cleat rearward on the shoe has the effect of raising your seat
by a lesser amount for that leg. The exact expression is messy,
but
for an upright bike, the effect is similar to raising your seat by
about y/3 for that leg, where y is the distance you moved the cleat
to
the rear. For example, if you move your cleat 6 millimeters to
the
rear, you might also want to lower your seat by about 2 millimeters.
Remember, though, that unless both cleats are moved rearward the same
amount, your other leg may feel that the seat is too low.
Another way to relieve pain in the ball of the foot is to use a custom
orthotic and/or a padded insole. Most cycling shoes provide poor
arch
support and even poorer padding.
After riding for a while with your aligned cleats if you find yourself
pulling out of the pedals while pedaling, you will need to tighten
the
release tension. After tightening the release tension the centering
force of the pedals will be higher, and you may discover that the
azimuth isn't optimum. Adjust the azimuth as described above.
On the other hand, if you find you never pull out of the pedals while
pedaling and if you find it difficult or uncomfortable to disengage
the cleat, try loosening the release tension. People whose knees
like some rotational slop in the cleat may be comfortable with very
loose cleat retension.
As with any modification that affects your fit on the bike, get used
to your pedals gradually. Don't ride a century the day after
you
install SPDs. Give your body about two or three weeks of gradually
longer rides to adapt to the new feel and alignment, especially if
you've never ridden with clipless pedals before. Several months
after
installing SPDs, I occasionally tinker with the alignment.
After performing the above adjustments if you are still uncomfortable,
seek additional help. Some people can be helped by a FitKit.
If
you're lucky enough to have a good bike shop nearby, seek their
advice.
-----------------
Tightening cleat bolts:
Tighten cleat bolts until they _begin_ to bind. This will happen
when
further tightening produces a vibration or squeal from the cleat.
Tighten no further or you may damage the mounting plate on the inside
of the shoe. After living for a while with a comfortable
alignment,
remove each mounting bolt separately, apply blue loctite on the
threads, and reinstall. Should you later find you need to loosen
a
bolt to adjust the alignment, you will have to reapply the loctite.
Keeping the Pedal/Cleat interface clean:
Occasionally you may find the pedals suddenly more difficult to
disengage. This usually happens because dirt or other contaminants
get caught in the cleat or pedal mechanism. I have found that
a good
spray with a hose quickly and cleanly washes off dust, mud, or other
gunk from the pedal and cleat. You may also wish to spray the
pedal
with a light silicone or teflon lubricant.
Acknowledgements:
John Unruh (jdu@ihlpb.att.com)
Lawrence You (you@taligent.com)
-----------------
Case History:
I have sensitive legs--feet, ankles, knees, tendons, etc. If the
cleats aren't aligned properly, I feel it. I took a long time
to find
a cleat alignment that was comfortable for long and/or intense rides.
I ride a Bridgestone RB-T, 62cm frame, triple chainring. I wear
size
48 Specialized Ground Control shoes--evil-looking black and red
things. They were the only shoes I could find in my size that
were
comfortable. When I installed the M737 pedals, I had 175mm cranks.
I set the release tension so that the indicator was at the loose end
but so that I could see the entire nut in the slot.
The azimuth I found most comfortable had both shoes pointing roughly
straight ahead. The ball of my left foot began hurting, so I
moved
the left cleat back about 4-6mm. This placed the ball of my foot
in
front of the pedal spindle. I did not make any left/right
adjustments.
Unfortunately, on longer rides, the ball of my left foot still hurt,
so I got a pair of custom CycleVac "Superfeet" insoles. I removed
the
stock insole from the shoe, and inserted the CycleVac insole.
The
CycleVac doesn't have any padding at the ball, and my foot didn't like
the hard plastic sole of the shoe. I had a pair of thin green
Spenco
insoles lying around, so I put those under the CycleVacs to provide
some padding. I didn't use the stock insoles because they are
too
thick. Finally, the pain was gone! If I remain pain-free
for a while
I may try moving the left cleat forward again.
Then I replaced the 175mm cranks with 180mm cranks, and I lowered the
seat 2.5mm. My left foot was still happy, but my right knee began
to
complain. Not only that, but my right foot felt as if it was
being
twisted to the right (supinating), toward the outside of the pedal.
After fussing with the azimuth of the right cleat, I couldn't find
a
satisfactory position, though I could minimize the discomfort.
I moved the right cleat as far as I could to the outside of the shoe,
bringing my foot closer to the crank. I also reduced the release
tension further. The red indicating dots are now just visible.
This
helped my knee, but my foot still felt as if it were being twisted,
as if all the force were being transmitted through the outside of the
foot. In addition, my left Achilles Tendon started to hurt at
times.
I lowered the seat another couple millimeters. This helped, but
I
felt that my right leg wasn't extending far enough. Then I tried
_rotating_ the saddle just a little to the right, so the nose was
pointing to the right of center. This helped. But my right
foot
still felt supinated, and my right knee started to hurt again.
I removed the right CycleVac insole and Spenco insole and replaced them
with the original stock insole that provides little arch support.
Bingo. The discomfort was gone. It seems I need the arch
support for
the left foot but not for the right foot.
How long will it be before I make another tweak? The saga continues...
-----------------
Copyright 1993, Bill Bushnell. Feel free to distribute this article
however you see fit, but please leave the article and this notice
intact.
------------------------------
Subject: 8.38 Rim Tape Summary
From: Ron Larson <lars@craycos.com>
This is a summary of the experience of riders on the net regarding
various rim tapes, both commercial and improvized. Any additional
comments and inputs are welcome.
RIM TAPE
Rim tape or rim strips are the material that is placed inside a
clincher rim to protect the tube from sharp edges of the nipple holes
and possibly exposed ends of spokes extending beyond the nipples. Many
materials have been used to produce rim tapes: plastic, rubber, tapes
consisting of a multi-directional fiber weave, duct tape and fiberglass
packing tape.
A few factors influence how well a rim tape works. Some of the tapes
are available in more than one width. It is important to choose the
width that provides the best fit to cover the entire "floor" of the
rim
as opposed to a tape that is barely wide enough to cover the nipple
holes. Another factor is how well the rim tape withstands the stress
of
being stretched over the nipple holes with a high preassure inner tube
applying preassure to it. The main form of failure of the plastic tapes
is for the tape to split lengthwise (in the direction the tube lies
in
the rim) under high preassure forming a sharp edge that the tube
squeezes through and then rubs against. Thus the splitting tape causes
the flat that it was supposed to be protecting against.
REVIEW OF RIM TAPES BY TYPE
Plastic Tapes
Advantages:
Easy to install and remove. No sticky side is involved.
Disadvantages:
Although there are exceptions, they are prone to splitting under
preassure.
Michelin Good Experiences: 0 Bad Experiences: 6
Cool Tape Good Experiences: 2 Bad Experiences: 0
Cool Tape is thicker than other plastic tapes and does not exhibit
the splitting failure noted above.
Hutchinson Good Experiences: 0 Bad Experiences: 2
Specialized Good Experiences: 1 Bad Experiences: 4
Rubber Tapes
Advantages:
Easy to install and remove. Good if the nipples are even with the rim
floor and there are no exposed spoke ends.
Disadvantages:
Stretch too easily and allow exposed nipple ends to rub through the
tape and then through the tape.
Rubber strips Good Experiences: 0 Bad Experiences: 2
Cloth tapes woven of multi-directional fibers:
Advantages:
Easy to install. Do not fail under preassure.
Disadvantages:
They are a sticky tape and care must be taken not to pick up dirt if
they need to be removed and re-installed.
Velox Good Experiences:11 Bad Experiences: 0
Velox rim tape comes in three different widths. Be sure to get
the
widest tape that covers the floor of the rim without extending
up the
walls of the rim. The stem hole may need to be enlarged
to allow the
stem to seat properly. Otherwise the stem may push back into
the tube
under preassure and cause a puncture at the base of the stem.
Non-commercial rim tapes
Fiberglass packing tape (1 or 2 layers)
Advantages:
Cheap. Readily available. Easy to install.
Disadvantages:
Impossible to remove. If access to the nipples is required, the tape
must be split and then either removed and replaced or taped over.
Fiberglass packing tape Good Experiences: 1 Bad Experiences: 1
Duct tape (hey, someone tried it!!)
Advantages:
CHEAP. Readily available.
Disadvantages:
Useless. Becomes a gooey mess that is impossible to remove.
Duct tape Good Experiences: 0 Bad Experiences: 1
CONCLUSION
While plastic tapes are easy to work with, they often fail. The clear
winner in this survey is the Velox woven cloth tape. A quick review
of
mail order catalogs confirms the experiences of the net. Velox was
available in 5 out of 5 catalogs checked. It was the only rim
tape
available in 3 of the catalogs. The other 2 had one or two plastic
tapes available. (None sold duct tape...)
One good suggestion was a preassure rating for rim tapes much like the
preassure rating of tires.
------------------------------
Subject: 8.39 STI/Ergo Summary
From: Ron Larson <lars@craycos.com>
This is the second posting of the summary of STI/Ergo experience. The
summary was modified to include more on STI durability and also the
range of shifting avaliable from each system. As before, I am open
to
any comments or inputs.
lars
THE CASE FOR COMBINED SHIFTERS AND BRAKES.
Shifters that are easily accessible from either the brakehoods or the
"drop" position are an advantage when sprinting or climbing because
the
rider is not forced to commit to a single gear or loose power / cadence
by sitting down to reach the downtube shifters. They also make it much
easier to respond to an unexpected attack.
At first the tendency is to shift more than is necessary. This tendency
levels out with experience. There is also an early tendency to do most
shifting from the bakehoods and the actuators seem to be difficult
to
reach from the drop position. This discomfort goes away after a few
hundred miles of use (hey, how many times have I reached for the
downtube on my MTB or thumbshifters on my road bike???). All
experienced riders expressed pleasure with the ability to shift while
the hands were in any position, at a moments notice.
The disadvantages are extra weight, added weight on the handlebars
(feels strange at first) and expense. Lack of a friction mode was
listed as a disadvantage by a rider who had tried out STI on someone
elses bike but does not have Ergo or STI. It was not noted as a problem
by riders with extended Ergo / STI experience. A comparison of the
weight of Record/Ergo components and the weight of the Record
components they would replace reveals that the total weight difference
is in the 2 to 4 ounce range (quite a spread - I came up with 2 oz
from
various catalogs, Colorado Cyclist operator quoted 4 oz of the top
of
his head). The weight difference for STI seems to be in the same
range. The change probably seems to be more because weight is
shifted
from the downtube to the handlebars.
There was some concern from riders who had not used either system
regarding the placement of the actuating buttons and levers for Ergo
and STI and their affect on hand positions. Riders with experience
have
not had a problem with the placement of the actuators although one
rider stated that the STI brakehoods are more comfortable.
ADVANTAGES OF EACH SYSTEM.
The Sachs/Ergo system was mentioned as a separate system. In fact
(according to publications) it is manufactured By Campagnolo for Sachs
and is identical to the Campagnolo system with the exception of spacing
of the cogs on the freewheel/cassette. With the Ergo system,
all
cables can be routed under the handlebar tape while the STI system
does
not route the derailleur cables under the tape. Those that voiced
a
preference liked the clean look of the Ergo system.
Both Ergo and STI seem to be fairly durable when crashed. Experience
of riders who have crashed with either system is that the housings
may
be scratch and ground down but the system still works. The internal
mechanismsof both systems are well protected in a crash.
Both Ergo and STI allow a downshift of about 3 cogs at a time. This
capability is very handy for shifting to lower gears in a corner to
be
ready to attack as you come out of the corner or when caught by
surprise at a stop light. Ergo also allows a full upshift from the
largest to the smallest cog in a single motion while STI requires an
upshift of one cog at a time.
Riders voiced their satisfaction with both systems. While some would
push one system over the other, these opinions were equally split.
------------------------------
Subject: 8.40 Roller Head Bearings
From: Jobst Brandt <jbrandt@hpl.hp.com>
Roller head bearings provided an advantage that is not directly
connected with rollers. However, compound ball and plain bearings
have recently replaced rollers as is described in the item on "Indexed
Steering". The main advantage of rollers was that they have two
bearings in one that is important because the bearing must accomplish
two functions. The problem of the head bearing is so obscure,
that
until recently, no one had taken into account that head bearing is
subjected different motion than is apparent.
The bearing serves as a hinge about which the front wheel assembly
rotates, but it also absorbs another motion, and this is the problem.
As the bicycle rolls over roughness, the fork absorbs shock mostly
by
flex just above and below the fork crown that makes it rotate fore
and
aft about a horizontal axis. The motion can be seen by sighting
over
the handle bars to the front hub while rocking the bicycle fore and
aft with the front brake locked. This is what occurs when rolling
down a paved road but with much smaller amplitude.
The angles through which the fork crown swivels are extremely small
in
contrast to the relative motion at the hub because the distance
between the hub and the fork crown is large. This motion is not
in
itself damaging to the bearing because it is only a small misalignment
that cup and cone ball bearings absorb easily. The damage occurs
when
these small motions occur when there are no steering motions to
replenish lubricant while the bearing balls fret in place. Fretting
breaks down the lubricant film on which the balls normally roll and
without which they weld to the races and tear out tiny particles.
Because rollers could not absorb these motions, they were equipped
with spherical backing plates hat could move in that direction.
This
was the contribution rollers made before they were replaced by ball
bearings that had this same feature. Balls, in contrast to rollers,
stay in alignment and do not bind up from sliding off center as
rollers often did.
See item on "Indexed Steering".
------------------------------
Subject: 8.41 Tubular Tire Repair
From: Jobst Brandt <jbrandt@hpl.hp.com>
Date: Mon, 20 Apr 1998 15:31:32 PDT
Opening the Tire
The tire casing must be opened to gain access to patch the tube.
To
do this, open the casing by peeling the base tape back and unstitching
the seam. If this is a seamless tire, chuck it. There are
two types
of seams, zipper stitch (using one thread) and two thread stitch.
The
zipper stitch is identified by having o