Newsgroups: rec.bicycles.tech
From: jbrandt@hpl.hp.com (Jobst Brandt)
Subject: Re: Un-Warping a rim
Date: Fri, 12 Jan 1996 19:59:36 GMT

Andrew Lavery writes:

> I've got a 'well used' Araya RM-17 lying around in my basement,
> which is warped pretty badly (to the point where I can't true it
> using the old loosen one spoke, tighten the other method).

The most convenient way to straighten a pretzeled rim is in situ.
Don't unspoke it but just loosen the spokes a couple of turns.  You
must bend the rim beyond its elastic limit so that it takes a set in a
nearly straight shape.  If you do not loosen the spokes first, you
will be trying to yield the rim while it becomes retensioned.  The
yield will put facets in the rim that cannot be corrected.

Place the wheel on the ground with the biggest excursion down and near
you.  Put your hands about 1/4 of the circumference apart on the rim
to either side of the wow and press down.  You will get a feel for the
resulting effect and how hard you must press to get a change.  Then
repeat this process each time looking for the worst excursion.  When
it is as good as you can make it, start tightening and truing the
wheel.  Finally, if there are zones with largely loose and tight
spokes on opposite sides, repeat the bending trick but with great
care.  Under tension the rim reacts much more quickly.

There is a book that describes all these operations in detail and with
diagrams.  You could probably use a copy.

Jobst Brandt      <jbrandt@hpl.hp.com>