The debate about Campy crank breakage continues -but unless I missed something a very important piece of info was left out of the messages I read. Yes - crank failure is typically (but not always as discussed below) a fatigue issue. But, riding style is extremely important in determining when the fatigue failue is likely. As engineering friends tell me, on every revolution of the cranks the rider puts a peak moment on the arm. Riders that are heavy and powerful but very even in their stroke may cause only a modest peak moment, while a choppy lightweight rider might actually put a higher moment on the arm. If I'm interpreting what I've been told correctly, the relationship between fatigue failure has I believe a square functional relationship to the peak moment. So, the choppy lightweight rider is much more likely to have a failure than the heavier, powerful, but smooth rider. This correlates well with some evidence I've seen. I know of one super strong rider (Olympic medal winner) who never broke much of anything. I then had a regionally strong local rider who came into Bicycle Classics inc. years ago who said he broke 27 crankarms - (some on the first day of use in one sprint! - not even a fatigue failure). And no, don't believe that cranks don't fail at the arm spider junction. Years ago I discussed this with a distributor and former Campagnolo employee who had seen many hundreds of failed cranks. Yes, they most often failed near the pedal, but he assured me that many also failed at the spider/arm junction. The kicker is that you can see the crack at the spider/arm junction but you can't usually identify an arm that is about to fail elsewhere. And finally, the idea that Campy NR arms are safe because "I've never broken one yet" is false. Yes, if you are a super smooth rider your risk is lower, but as the miles go on the probability of a failure increases. No matter what your past experience kids you into believing, the risk of failure is increasing with every stroke. Mike Kone in Boulder CO
> In a message dated 9/14/2004 2:08:23 PM PST, gpvb1@comcast.net writes:
\r?\n> Absolutely, don't ride the old Campy cranks. Instead, send them postage
\r?\n> pre-paid to me, and I will see that they are properly recycled. If they are
\r?\n> clean-looking Strada 175s, I may even split the postage with you! ;-)
\r?\n> It has been my experience that some folks experience breakage of these, and
\r?\n> the vast majority of us don't. It doesn't correlate well to rider weight or
\r?\n> power or fitness level, or even to the vintage or age of the cranks to some
\r?\n> extent (although I would say that generally the ones that break are from 1968 to
\r?\n> about 1985, i.e. the "classically" shaped 144 BCD ones - the earlier "boxy" ones
\r?\n> had a beefier cross-section and that seems to be a factor). It does correlate
\r?\n> very strongly to the total mileage on them, as it's a fatigue failure. As
\r?\n> Phil stated, these have some well-known failure modes, but in nearly three
\r?\n> decades of riding them almost exclusively, I've never broken one, nor has my
\r?\n> wife,
\r?\n> nor has anyone I've ever ridden with on a regular basis. Recently, I replaced
\r?\n> my wife's SR cranks at about 70,000 miles pre-emptively, more for cosmetic
\r?\n> reasons than concern over any impending failure. It certainly does happen,
\r?\n> though,
\r?\n> and somewhat more often with these old cranks than with most other comparable
\r?\n> old cranks of the same period. Check out Damon Rinard's site of crank
\r?\n> failures for pics. of lots of brands of broken crank arms. It's sobering, but it
\r?\n> doesn't stop me from using them.Check for cracks often!
\r?\n> Regards, Greg Parker
\r?\n> -----------------------------------------------------------------------------
\r?\n> Greg-
\r?\n> It sounds like your experience has been a lot like mine, especially the 1985+
\r?\n> SR/NR models. Even though I think its out of the "CR timeline", that's the
\r?\n> time that Campy got wise about designing in extra material at the
\r?\n> spider-arm/crank arm junction. You probably know them as the non-fluted crankarm
\r?\n> design,
\r?\n> but other manufacturers, i.e., Gipiemme were designing in that extra-beefiness
\r?\n> about 4 or 5 years before Campy. In any case, my experience is a lot like
\r?\n> yours, I have never had any cranks break on me, but have seen after 10+ years
\r?\n> riding the same crank, very minor stress cracks did start to form at that
\r?\n> critical
\r?\n> junction. I am sure everybody is aware of the most common prophylactic for
\r?\n> this problem is to file smooth the "stress-risers". I have had nothing but good
\r?\n> luck with this method.
\r?\n> Cheers-
\r?\n> Dave Anderson
\r?\n> Cut Bank MT