Subject: Re: crank arm shape Posted by: Randy Shoquist on December 13, 2000 at 04:28:13: In Reply to: crank arm shape posted by Kiwi on December 07, 2000 at 02:54:34:

Message: >I've noticed that the Ultegra crank arms on my race bike >are curved, and those on my old ride-to-work Campag equipped bike are straight. The dimension between the >ends of the Ultegra cranks is 10mm greater than the Campag >ones, for an identical BB width. Is one design superior >to the other? Or is this more an appearance issue? Is there any penalty in pedalling efficiency? Cheers! In the days of yore when Campagnolo Nuovo Record reigned supreme o'er all the realm, front derailleurs were but simple devices, with thin, flat outer cage plates. Then they got much more sophisticated, with much more shape to the outer plate, requiring more clearance between the chainring and the crankarm. Second, aluminum frames typically have fatter chainstays than steel and thus are wider where the crankarm ends pass, again requiring a modification to crankarm shape. (I had to use a longer BB spindle to fit my old Campys to a Specialized M2 frame.) Third, BB spindles got shorter in an effort to reduce flex. Another reason to change crankarm shape. And I think you're right about appearance. Designers probably think that curved or angled crankarms look more sleek. As for "Q factor" I think Jim is correct. I certainly prefer a narrower pedal stance, although I get along OK with my wide-Q tandem. Also, many people walk, and presumably pedal, with their feet angled outward. They may benefit from the extra ankle clearance.