markjgi-@yahoo.com
to check to fork it pretty simple. Most shops should
have a set of campy "cup" tools, that let you in
essesence put the cups open end towards each other in
the fork dropouts. You adjusts them so the open ends
are close together. IF the dropouts are parallel, then
the lips of the two cups are parallel. If the dropouts
are not, then the lips of the cups are visiblly out of
allignment.
no need to send stuff to Calfee in less you want to, a
local shop should be able to check with the fork still
on the bike.
Calfee is right tho, steel can be "cold forged" which
means bent. Carbon and aluminum are either straight or
not. The only fix for them, is the garbage can.
Mark Ginsberg
--- Ron Magnus <ro-@hevanet.com> wrote:
Hello everyone,
Earlier this year there was a thread running for a
week or so concerning why
some bicycles have wobble or shimmy at certain
speeds. What follows is an
explanation from a credible source that should clear
the air. Enjoy the
reading!
Ron Magnus-Portland, OR
The following was sent to our dealers last
month:Calfee Design has
identified a cause of speed wobble (a.k.a. shimmy)
and instability that can
be prevented. Speed wobble is a dangerous condition
that can cause the rider
to lose control of the bicycle and crash. While
loose headsets and out of
true wheels and frames can contribute to
speedwobble, we have found that
fork asymmetry can also cause speed wobble. Fork
symmetry is defined as the
symmetrical position of the forkdropouts in relation
to the steering axis.
Specifically, the equality of the distances from the
dropout faces to the
steering axis must be within a certain tolerance for
the bike to ride in a
stable and confident manner. Traditionally, steel
forks were cold set after
welding or brazing torealign them after possible
distortion caused by the
heating and cooling of the metal. A diligent steel
frame builder can align
the fork blades to within a millimeter of symmetry.
Carbon fiber forks
cannot be cold set. They must be molded straight To
begin with. We have
found that a small percentage of carbon forks by
various makers were molded
with asymmetrical fork blades. Some are Off by a
little over a millimeter
and others are off by two or more. Forks that are
off by over 1.8
millimeters in symmetry have a good Possibility of
being prone to speed
wobble. A symptom of a fork that is off by 1.8 mm
or more is a noticeable
difficulty when riding no hands at a slow speed
(less than 10 mph). One has
to lean to the side slightly to keep going
straight. A bike with
asymmetrical forks seems to corner better in one
direction but not so well
in the other. At speeds of 30 mph or more, the bike
can develop speed
wobble. If your bike has the above-mentioned
symptoms, the fork should
bemeasured for symmetry. This is difficult to
measure without propertools.
Calfee Design measures all forks for symmetry and is
equipped tomeasure any
fork. If any Calfee customer wishes to have their
forkchecked, please send
it to us with a letter requesting a forkinspection.
Non-Calfee customers may
send their forks for inspection for a nominal fee.
Replacements may be
available for asymmetrical forks, depending on the
individual fork maker's
policy. Craig Calfee
To respond to the whole group send to
ob-@topica.com.
To respond to the list manager send to
cmur-@obra.org
To unsubscribe send to obra-uns-@topica.com
Mark J. Ginsberg
Attorney At Law
621 SW Morrison St., Ste. 900
Portland, OR 97204
(503) 542-3000
Fax (503) 227-2530
markjgi-@yahoo.com
www.bikesafetylaw.com
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