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Path: utzoo!watmath!clyde!burl!ulysses!gamma!mb2c!aat!sleat
From: sleat@aat.UUCP
Newsgroups: net.bicycle
Subject: Re: PROBLEM:  My new chain is skipping...
Message-ID: <298@aat.UUCP>
Date: Tue, 8-May-84 20:39:22 EDT
Article-I.D.: aat.298
Posted: Tue May  8 20:39:22 1984
Date-Received: Wed, 9-May-84 02:30:36 EDT
References: <978@wateng.UUCP>
Organization: Ann Arbor Terminals
Lines: 39


Among the alumni of the Naked Wrench Bicycle Co-Op, this is reffered to
as Garcia's Syndrome.  I no longer remember who the original Garcia was,
but he had this problem.  We use to see it all the time.  It is indeed due
to the fact that the teeth on your rear cogs are worn, and yes indeed,
as your new chain wears out, the problem will go away.

Consider the situation:  Neither the chain nor the cog teeth are very
flexible.  If the pitch of the chain is just a slight bit different from
the spacing of the teeth, all of the load will be born by the cog and
link closest to the source of tension.  As the link rolls off that tooth,
the load is suddenly transferred to the next link/tooth pair.  This, by
itself, simply produces a rough "lumpy" transmission of power.  If the
difference in pitch is great enough, as the chain shifts you get, in
effect, a wave propagating around the cog from the feed side, and it skips
a link.  This is a little hard to describe without diagrams, so you'll
just have to work it out.

You shouldn't need to replace the freewheel every time you replace the
chain.  The point is that unless the pitches are very closely matched,
they will wear at a much higher than normal rate until they are matched.
So, if you keep your chain well lubricated and clean, and replace it every
few thousand miles, your freewheels and chainrings should last a long
time.  (Again, this implies starting with an unworn freewheel.)

If you have just one rear wheel or freewheel, then you could simply wait
for your chain to wear out a bit and forget the problem until next time.
If you want to be able to change wheels or replace the chain without
this problem, you pretty much have to replace that freewheel.

Incidentally, the two extreme chainwheel/freewheel combinations, small/small
and large/large are generally best avoided due to the angle the chain must
make.  This is particularly true of 12, 15, or 18-speed setups.


Michael Sleator
Ann Arbor Terminals
{cbosgd, mb2c, psu-cs, uofm-cv, cosivax}!aat!sleat