[CR]Campy Crankarm Breakage & Bearings

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Date: Thu, 27 Jun 2002 13:09:21 -0400 (EDT)
From: "Stephen Barner" <steve@sburl.com>
To: <classicrendezvous@bikelist.org>
Subject: [CR]Campy Crankarm Breakage & Bearings

On the topic of Campy crank cracks, I was with a guy many years ago when he broke off his right campy NR crankarm. He came down on the TT pretty hard, which certainly spoiled his ride. He was a big guy, 250 lbs, and a very strong rider. He said it was the third Camp crank he had broken and refused to ride them ever again.

I have two right arms with cracks. One I purchased and don't know the history of. It actually has cracks on both sides of the arms and I sure wouldn't ride it. The other was originally on a Masi that I purchased many years ago, and now lives on my Marinoni. I checked the spider web and, sure enough, it had a crack about 2mm long. It seems that the design defect is the sharp edge formed in the web, which acts as a stress riser.

I read once that it is not a question of whether a metal component subjected to periodic stress will fail, but when. You can design a partso that it will not fail during its design life, but eventually it will subjected to periodic stress will fail, but when. You can design a part so that it will not fail during its design life, but eventually it will fatigue and fail. Since I like to make things last as long as possible, I took a file and filed out the area of the crack, leaving a slight radius. I hope this will relieve the stress and keep the crack from reappearing in my lifetime. Every ten years, I'll let you know how it is doing.

On the bearing thread, I was once told that Campy kept significantly closer tolerances on their ball bearings than standard Grade 25 balls. It is also my understanding that Grade 25 bearings are made to spherical tolerance of +- 0.000,000,025 inch. I vaguely recall a claim that Campy's bearings where made to a spherical tolerance of 0.000,000,002 inch. There are other parameters that effect bearing quality as well, notably surface finish, but I wonder if anyone else was drinking the same beer I was in those days and had similar halucinations? Anybody have a copy of the Bearing Cyclopedia handy and can look up the specs for Grade 25 bearings? I do recall that I tried building up a Campy road headset with loose Grade 25 balls one time and didn't like the results. When I put a new set of Campy retainers in, that old Vicenza smoothness returned.

One last item--anyone in SW Cal. want to go for a ride this weekend? I am in San Diego with my Bianchi for a few more days.

Steve Barner, Bolton, Vermont--Home of the Huffy Throw Hall of Fame