Re: [CR]Campagnolo crank breakage?


Example: Production Builders:Frejus

Date: Mon, 23 Jun 2003 08:44:44 -0700
From: Steve Maas <smaas@nonlintec.com>
To: marcus.e.helman@gm.com, classicrendezvous@bikelist.org
Subject: Re: [CR]Campagnolo crank breakage?
References: <OFE7861996.458F92B5-ON85256D4E.00531D66@mail.gm.com>


This is apparently true. There is a some discussion of this on rec.bicycles.tech, which I recommend. The great guru of all things technical regarding bikes (and a lot else, apparently) Jobst Brandt, has expounded on this frequently.

The problem is related to the thin web of metal between the crank arm and the spider. This is a stress concentrator; cracks start at this point and quickly propagate. Another point associated with failure is around the pedal hole in the crank arm. If you see cracking, however small, in either of these places, you should not ride on the thing at all, and replace it immediately.

Some people file out the web with a rat-tail file, to minimize the stress concentration. I don't know if that really does more than a little good, since there isn't a lot of material that can practically be removed. Still, I've done it on a couple cranks, on the theory that even a little improvement is better than nothing.

There is a little more info in the FAQ at http://draco.acs.uci.edu/rbfaq/FAQ/8f.10.html

Steve Maas (a dreary morning in) Long Beach, California

marcus.e.helman@gm.com wrote:
> At the risk of sounding like that Gilda Radnor character on SNL, what's all
> this I hear about Campagnolo cranks being subject to sudden catastrophic
> failure? Is it true? Do I really need to closely inspect my cranks before
> each ride?
>
> Thanks,
> Marcus Helman
> Huntington Woods, MI