Archive-name: bicycles-faq/part3

[Note:  The complete FAQ is available via anonymous ftp from
draco.acs.uci.edu (128.200.34.12), in pub/rec.bicycles.]

------------------------------

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>

Two points here:

1. The jamb 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.

2. Breaking off stems with a frame pump comes from pumping
   incorrectly.  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 is $1000 in California.  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 should be treated under its
   own heading.

------------------------------

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 the use of the term brinelling
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 an "indexed" head bearing.

Damage to the head bearings seems to be twofold in this case because the
steering, if properly adjusted, only gets looser from dimpled bearings and
would not become arrested by the dimples.  So the head was adjusted too
tight or it got tighter inadvertently.  However, dimpling is caused by
lubrication failure and occurs while riding straight ahead.  This condition
is worsened by a tight bearing while a loose bearing would introduce more
lubricant if it were to rattle.

If you believe it comes from hammering the balls into the races, I suggest
you try to cause some dimples by hammering with a hammer onto the underside
of the fork crown of a clunker bike of your choice.  Those who pounded in
cotters on cottered cranks will recall no such dimpling on the BB axle and
even though this is a far smaller bearing race than a head bearing and the
blows are more severe and direct, no dimples were made.

Ball bearings make metal-to-metal contact only when subjected to fretting loads
(microscopic oscillations) while in the same position, as in riding straight
ahead on a conventional road.  If you watch your front axle while rolling
down the road at 20+ mph you will notice that the fork ends vibrate fore and
aft.  This motion arises not at the blade tips but at the fork crown and
articulates the head bearing in fretting motions that are not in the normal
direction of bearing rotation.  Any substantial steering motion replenishes
lubrication from adjoining areas.

Lubrication failure from fretting causes welding between the balls and
races and these tiny weld spots tear out repeatedly.  The result is that at
the front and rear of the races elliptical milky dimples occur.  Were these
brinelling (embossed through force) they would be shiny and round.  Various
testimonials for the durability of one bearing over another may be based on
good experience, however, the differences in most of these was not in the
design of the bearing but rather the type of lubricant used.  A ball bearing
is not suitable for this use.  This is in spite of their use in almost all
bicycles.

To reduce point loads and to protect the rolling elements from fretting
motion, roller bearing head bearings have been built.  In these the rotary
motion is taken up in needle bearings on conical races and the fork
articulation is absorbed by an approximation of a spherical cup (the steel
race) against the aluminum housing.  Both of these bearings are ideally
loaded.  The rollers all remain in contact and carry rotary motion while
the plain spherical bearing remains in full contact carrying low pressure
fore and aft motion.

I am disappointed that roller bearings until now have not been suitably
perfected to rid us of the age old bearing failure.  Maybe some day soon
Sun Tour, Campagnolo, Shimano or Stronglight will emerge with an easily
adjustable and fully compatible bearing.  The one I am using is durable but
not easily adjusted and it has too great a stack height to qualify for a
recommended replacement.

------------------------------

Subject: 8.24  Center Pivot vs. Dual Pivot Brakes
From: Jobst Brandt <jbrandt@hpl.hp.com>

Sidepull (one central pivot) brakes operate at a small angle to the
rim.  That means the pad moves in a nearly perpendicular direction to
the braking surface and the pads can be completely worn down without
adjusting their position.  The unit is light and has a self contained
quick release and cable adjustment feature.

Its weakness is its thin arms that, in the pursuit of light weight,
flex in the bending direction.  With the current practice to minimize
tire clearance on road bicycles, sidepull brakes cannot be used off
road for lack of dirt clearance.  Their return spring is anchored in a
way that relative motion occurs between it and the brake arms.  This
motion demands lubrication and in its absence the brake does not
center itself.  This is a perpetual problem that has not been solved
and has given rise to many designs, the latest of which is the Shimano
dual pivot brake.  This brake has the disadvantage that it cannot
track a wobbly wheel because it is forced to be centered.

The cantilever and centerpull brakes are inversions of the same
design.  Both have pivot points that are at 45 degrees to the brake
surface, but the centerpull offers no advantage over sidepulls because
it has all the same problems and not the advantages.  In contrast the
cantilever is the most rigid of available brakes and offers more tire
clearance for off road use.

The approach angel moves the brake pads in an undesirable direction so
that as the pad wears it must be adjusted to prevent falling off the
rim.  With wear, the centerpull goes into the tire while the
cantilever allows the pad to pop under the rim, never to return.
Cantilever brakes have the additional problem that their reaction
force spreads the forks.  For this reason, U shaped stress plates are
made to contain this force.  For forks with telescopic suspension,
braking restricts forks motion.

Nearly all bicycle brakes have about the same mechanical advantage
(4:1) that arises primarily in the hand lever.  The "calipers" all
approximate a 1:1 ratio.  This is necessary to fit the reach of the
average hand and the strength of the hand in proportion to body
weight.  That is to say all brakes are made to about the same human
specification.  Force and motion are a trade-off and this is the
result.

The Campagnolo Delta and Modolo Chronos brakes have a variable ratio
that at the extremes ranges from infinity to zero, its motion being
generated by an equilateral parallelogram that changes from one
extreme to the other.  This is an undesirable feature, especially as
the pads wear and braking takes place in the zone of increased lever
travel and increased mechanical advantage.  The brake bottoms out
abruptly.

Servo activation on cantilever brakes has been offered in a design that
uses the forward thrust on the brake post to add force to the
application.  Self servo effects are undesirable in brakes because the
proportionality between braking and hand force is lost.  You don't
know how much braking you will get for a given hand lever force.  It
can vary widely and in some circumstances cause an unwanted skid.

------------------------------

Subject: 8.25  Seat adjustments
From: Roger Marquis <marquis@well.sf.ca.us>

     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 the 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:
      1) ZERO TO ONE HALF CM. for recreational riders
         (-50 mi/wk.),
      2) ONE HALF TO ONE CM. for experienced riders
         (50+ mi./wk.),
      3) ONE TO TWO 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.
 
------------------------------

Subject: 8.26  Cleat adjustments
From: Roger Marquis <marquis@well.sf.ca.us>

[Ed 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.]

     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.
     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.

------------------------------

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 provide an advantage that is not directly
connected with rollers.  Their main advantage is that they have two
bearings in one and this is important because there are two functions
this bearing must accomplish.  The problem of the head bearing is not
obvious to most users or to the manufacturers or they would do
something about the miserable state of affairs.

The head 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
partly by flex in the steer tube, and this flexing makes the fork
crown rotate fore and aft.  The motion can be seen by sighting over
the handle bars to the front hub while riding and is more pronounced
for the taller heavier riders who also experience most of the head
bearing failures.

The angles through which the fork crown swivels are extremely small in
contrast to the 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 such bearings
absorb easily.  The damage is caused by the lack of substantial
steering rotation while the bearing is fretting in place.  Fretting
breaks down the lubricant film on which the balls normally roll and
without which they will weld to the races and tear out tiny particles.

Fretting that causes lubrication failure occurs most often during fast
straight-ahead road riding where few steering motions occur to
replenish lubricant.  Typically, coasting down long fast descents
rather than rough, jarring trail riding causes dimples in the head
bearings.  The removal of small particles from the races give the
milky texture to the dimples that are often attributed to brinelling.
They are not embossed into the races but are eroded by fretting and
welding.  Once initiated the dimples grow because the balls prefer to
return to the depressions.  As the process progresses the bearing
becomes loose and if adjusted, is tight when not steering straight
ahead, thereby giving the indexed response.

A solution is to separate steering from suspension motion.  This can
be done by using a rolling bearing for low friction steering and a
large plain bearing for the fore and aft tilt of the fork crown.  This
is where the needle bearing comes into play.  Conical steel cups that
approximate a spherical bearing ride in a plain aluminum body to
support the fork crown tilt.  The pressure of a large area plain
bearing is low enough for good lubrication even with fretting while
steel rollers that approximate a tapered roller bearing give low
friction steering.  The rollers run on the backs of the steel cups
that are the plain bearing.  The curvature of a true spherical cup
would be so small as to be invisible, as would the precise taper of a
needle for such a design.  The approximations are appropriate.

The entire bearing is relatively inexpensive, having no precision
races, special hard alloys, or complicated formed steel cages.  Needle
bearings are as inexpensive as balls and a plastic cage holds them in
true radial alignment.  The steel cups are actually bellville shaped
hardened washers and the housings are turned aluminum parts.  It would
be wasteful to combine a ball assembly with the spherical alignment
cups because these cups lend themselves to supporting rollers without
modification.  Balls, in contrast, need curved races.  I expect other
major manufacturers to take up this design soon.

------------------------------

Subject: 8.41  Tubular Tire Repair
From: Jobst Brandt <jbrandt@hpl.hp.com>

Opening the Tire

To patch the tube, you must get into the tire and requires opening 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 only one thread.  It appears to make a
pattern of slanted arrows that points in the direction in which it can
be 'unzipped'.  Never open more tire than is necessary to pull the
tube out of the casing.  Remember, the tube is elastic and can be
pulled out of a three cm long opening pretty well.  Even if there are
two punctures not too far apart, the tube can be pulled out of a near
by opening.  If you must insert a boot, you'll need to open about 6 cm
or about the length of the boot and then some.

Base Tape

Never cut the base tape because it cannot be butt joined.  Always pull
it to one side or separate it where it is overlapped.  (also: Don't
cut the tire seam, pull out the stitches.)  When working on the stem,
only unstitch on one side of the stem, preferably the side where
machine finished.  Use latex to glue down loose threads on a sidewall
cut.  Paint the exposed casing zone that is to be covered by the base
tape and the base tape with latex emulsion, allow to partially dry and
put the tape in place.  Put the tire on a rim and inflate hard.

Zipper Stitch

Cut the thread at some convenient place at the upstream end of the
opening and, with a blunt awl like a nitting needle, pull out a few
stitches in the direction the stitch pattern points.  Once you have
exposed a length of thread, you can pull the stitching out like a
zipper.  When you have opened enough, take the loose end and run it
through the last loop that has not yet been pulled to lock the zipper.
If you think the thread is good enough, don't cut it off but use it to
re-sew the seam.

Two Thread Stitch

One of the threads makes a zig zag as it locks the other thread where
it penetrates the tire casing.  Cut both threads near the middle of
the opening and, with a blunt awl like a nitting needle, pull out a
the locking thread in both directions.  The locking thread is the
easier one to pull out so remove as many stitches as you'll need to
get into the tire.  The other thread pulls out like a zipper.  Tie a
square knot with the loose ends at both ends of the opening and cut
off the rest.

Patching

Patch butyl (black) tubes using patches from a bicycle patch kit.

To patch a latex tube make patches from an old latex tube that are
fully rounded and just large enough to cover the hole plus five mm.
For instance, a thorn hole takes a 10 mm diameter patch.  Use Pastali
rim glue wiped thinly onto the patch with your finger.  Place the
patch on the tube immediately and press flat.  Latex will pass the
volatile solvent allowing the glue to cure rapidly with good adhesion
to the tube.

Casing Repair

Repairing tubular tires requires latex emulsion.  You can get it from
carpet layers, who usually have it in bulk.  You must have a container
and beg for a serving.  If you are repairing them you probably ride
tubulars, and therefore, will have dead ones lying around.  The best
tubulars generally furnish the best repair material.

Most cuts of more than a few cords require a structural boot.  For
boot material, pull the tread off a silk sprint tire, unstitch it and
cut off the bead at the edge of the fold.  Now you have a long ribbon
of fine boot material.  Cut off a 50cm long piece and trim it to a
width that just fits inside the casing of the tire to be booted from
inside edge of the bead (the folded part) to the other edge.

The boot must be trimmed to a thin feathered edge so that the tube is
not exposed to a step at the boot's edge, otherwise this will cause
pinholes in a thin latex tube.  Apply latex to the cleaner side of
the boot and the area inside the tire.  Insert the boot and press it
in place, preferably in the natural curve of the tire.  This makes the
the boot the principal structural support when the tire is again
inflated.  If the casing is flat when the boot is glued, it will
stretch the casing more than the boot upon inflation.
After the boot dries, and this goes rapidly, sew the tire up.

Tube Replacement

To replace the entire tube, open the tire on one side of the stem, the
side that seems to be easier to re-sew after the repair.  Open about
eight to ten cm the usual way and pull out the old tube by the stem
locally.  Cut the tube and attach a 1/16" thick nylon cord to the
loose end of the tube to be pulled through the casing as you pull the
old tube out.

Cut the "new" latex tube about 5 cm away from the stem, tie the cord
onto the loose end and pull it gently into the casing.  Dumping some
talc into the casing and putting talc onto the tube helps get the
tube into place.  With the tube in place, pull enough of it out by
stretching it to splice the ends together.

Splicing the Tube

This procedure only works with latex tubes.  Overlap the tube ends so
that the free end goes about one cm inside the end with the stem.
With the tube overlapped, use a toothpick to wipe Pastali rim cement
into the interface.  The reason this MUST be done in place is that the
solvent will curl the rubber into an unmanageable mess if you try this
in free space.  Car