Jerome & Elizabeth Moos wrote:
> Well, I don't know, I've heard several reports of riders winding up
> on the pavement when a Campy crank broke during a hard downstroke,
> throwing them completely off balance. This is probably more likely
> to happen if the crank fails at the pedal hole rather than at the
> spider. But Campy NR cranks were prone to cracking there also. In
> fact the nastiest cracks I've found in Campy NR cranks have been at
> the pedal hole.
Ok, but that's probably the exceptional case in a crank failure. With a
stem failure you *WILL* lose control every time. When my (off-topic,
non-AVA) stem failed, I was leading a pace line at 20+ mph and barely
had time to think "what the h..." before the bike was off the road and
airborne over a drainage ditch. I consider myself lucky because the bike
went to the right and dumped me on a nice soft suburban grass lawn
rather than to the left into oncoming traffic and asphalt. If it had
gone the other way I'd probably have ended up as a hood ornament on an
SUV rather than just suffering the collapsed lung and broken ribs. As it
was, my bike was otherwise undamaged except for some grass stains!
> Maybe I'm too complacent, but I remain unconvinced that quality alloy
> bicycle components fail catastrophically and without warning any more
> frequently than say humans being struck by lightning or being killed
> by an airplane crashing into their house. In my experience, alloy
> components have always shown visible cracks well before actual
> failure. So I continue to ride AVA bars, AVA stems, Campy NR/SR
> cranks and ALAN aluminum frames. I just inspect them regularly for
> cracks. And if I detect cracks, the component is removed immediately
> and used for display only.
Be that as it may, but aluminum does not fail gradually like steel, but catastrophically, going from an initial crack to complete failure very quickly -- sometimes in a matter of only a few stress cycles.
--
John (john@os2.dhs.org)
Appleton WI USA