From personal experience, the stresses on the drivetrain while touring far exceed the stresses while racing. Recently, we went for a weekend trip, and my Mercian was loaded with camping gear for three, a trailer and a 30-lb. 2-year-old. The Mercian has horizontal dropouts and Campy C-Record hubs. (I had replaced the broken axle prior to the trip.)
Several times when starting from a light, the rear wheel pulled out of the dropouts. I tightened the QR as much as reasonable, but to no avail. I finally "learned" to start using a very light touch, and that helped.
In all my years of racing (up to a Cat. 2), using Campy NR hubs and horizontal dropouts, I never had a wheel pull out during a sprint (fortunately, I might add - I might not be around to tell the tale).
Why? I don't know, but I suspect the reason is simple: When Cipollini pushes on the cranks, the bike has the option of going forward to alleviate the stress. A loaded touring bike puts up much more resistance... and thus stresses the entire drivetrain much more.
But we are getting away from classic bikes here.
Jan Heine, Seattle
>
>From: Tom Dalton <tom_s_dalton@yahoo.com>
>Subject: Re: [CR]Predicting/preventing NR/SR crank breakage
>To: classicrendezvous@bikelist.org
>
>
>Jerry & Liz Moos wrote:
>I suspect that laboring up a mountain pass with 50 lbs of gear
>stresses a crank as much as a Cippolini sprint.
>
>Sure, and the crankshaft in my Chevy Nova gets just as much stress
>as the crank in Michael Schumacher's Ferrari... Ugh!