It is important to remember that this procedure only helps reduce the chance of a failure at the arm/spider junction. Yes, many failures happen there - but perhaps more fail near the pedal spindle usually on the left arm (but not always).
Failures seem to be highly correlated to riding style, though cranks with mega miles under lighter weight riders can fail too - and without warning.
Despite my reputation for being a doom and gloomer about Campy NR cranks I've never broken one and I ride them quite a bit (but not any with huge miles on them).
On this mornings ride, I rode Campy 50th anniversary cranks on a Baylis frame for a fun 50 mile jaunt into the mountains. Try as I might I wasn't able to break the crank. And the Baylis has an amazing ride - Brian in my opinion has found the cutting edge of performance with skinny tubes (oversize is different - not necessarily better) and has the whole fork rake/head angle trail thing mastered better than anyone else I know. The bike is so quick, yet has the glued to the ground rock steady feel on steep downhills. Most bikes can do one or the other, but this does both better than any other machine I've ever ridden.
Mike Kone in Boulder CO.
At 06:19 PM 5/15/02 -0400, Mark wrote:
>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.
>Mark Cutrufelli in
>[mailto:firstname.lastname@example.org]On Behalf Of Mark Bulgier
>Sent: Wednesday, May 15, 2002 4:48 PM
>Subject: RE: [CR]Was Paletti - Now Cracked crankarms
>Charlie Young wrote:
>> Help me out here folks. I see what appears to be the crack:
>> 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.