[CR]crackeded crankarms


Example: History:Norris Lockley

Date: Wed, 15 May 2002 18:19:06 -0400
From: Mark <rena.cutrufelli@comcast.net>
In-reply-to: <C102531FB711D411B5B90060B0A468760DADA0@mail.bulgier.net>
To: Mark Bulgier <mark@bulgier.net>, classicrendezvous@bikelist.org
Subject: [CR]crackeded crankarms

The LBS did my SR crank as a preventive measure using a dremel tool only-Filed the point where the arm meets the spider. The guy who described this procedure sent arrows back on my internet pic showing where to file. "Do this and it will last forever" he said. How could I ignore it? Sheldon Brown also gave me further advice on this issue before I was a listmember.He thought my cranks had had only light use anyway, and he commented a bit more on frequency of occurrence.. Thanks Sheldon!But I went ahead just to have the LBS file the sharp corner to be doubly safe. So quick, so easy. Never heard of following up with polish. I was too ignorant to know that this preventive procedure, with some variations apparently, was common.I am anything but a hard grinder anyway, so the risk was probably low for a number of reasons.

Best Wishes, Mark Cutrufelli in Laurel,MD

-----Original Message----- From: classicrendezvous-admin@bikelist.org [mailto:classicrendezvous-admin@bikelist.org]On Behalf Of Mark Bulgier Sent: Wednesday, May 15, 2002 4:48 PM To: classicrendezvous@bikelist.org Subject: RE: [CR]Was Paletti - Now Cracked crankarms

Charlie Young wrote:
> Help me out here folks. I see what appears to be the crack:
>
> http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=1829066549
>
> Is this particular crankarm toast or can it be reclaimed by
> filing down to the innermost extent of the crack?

I'd expect that is salvageable. I've filed and ridden worse anyway. But other than armchair cogitatin', I don't have any real evidence of the lifespan of cracked cranks, with and without filing. Anybody else have anything more definitive?

I use a tiny needle file (about 1/8" diameter; that's 3mm in Communist countries ;^), file all the crack out, then round and fair all the edges where I filed, then smooth out the filemarks, usually with something like 220 grit paper or cloth followed by 400 grit. I do believe that filemarks are coarse enough to be stress concentrations that might initiate a crack down the road, even from my fine needle file. Ideally the whole area would be polished, but I stop where I imagine the point of diminishing returns to be. I haven't done it lately, but I imagine it's about a 20-minute job, and it's worth it to me if only for the placebo effect.

I'd love to hear others' methods and results.

Mark Bulgier
Seattle, Wa
USA