If I recall my framebuilding classes correctly the UCI requires a minimum 58cm distance from the center of the BB to the center of the front axle. Short frames will have the same clearance just a shallower
head angle. (and therefore a longer fork rake)
Steve Leitgen La Crosse, WI
On Jan 9, 2006, at 7:16 PM, Fred Rafael Rednor wrote:
> Manny, (please forgive me if I'm being overly familiar),
> Here's my experience as a relatively long legged short guy
> on 51cm to 53cm frames:
> 1) I have NEVER ridden a lightweight frame for 700c or 27"
> wheels that did not have some toe (clip) overlap.
> 2) The top tube lengths varied from 52cm to almost 55cm. It
> looks to me that head tube angles were always about 72 degrees
> (perhaps 73 on my LeJeune tandem and maybe 74 on the track
> bikes.)
> 3) In general, this has never been a problem, although I have
> not ridden with cranks longer than 170mm on a reagular basis.
> 4) Here are the moments when it has been a slight
> inconvenience:
> a) Hollands frame with 52cm top tube (170mm cranks): you need
> to keep your wits about you (and "time" your strokes) on _very_
> tight turns at _very_ slow speeds.
> b) Witcomb fixed gear with 53cm top tube (165mm cranks):
> similar to above; and also at a dead stop (say at a traffic
> signal) my leading foot can hit the tire if I have to turn the
> wheel. So I lift the rear, and rotate the cranks a few degrees
> and then turn the wheel.
> That's it - no problems, otherwise. As for Merckx...
> He rode much larger frames so overlap might never have been an
> issue at all. Even if he had some frames with short top tubes,
> he probably never was going slowly enough for it to be a
> problem.
> What about Luison Bobet, a short guy who rode with long
> cranks? Perhaps in his case it was also never a problem
> because he never was going that slowly?
> Cheers,
> Fred Rednor - Arlington, Virginia (USA)
>>
>>
>> How common was this on on-topic bikes, especially in
>> the mid- to late 70s when short wheelbases became in
>> vogue?
>>
>> Is it a problem in real riding conditions?
>>
>> I have 172.5mm cranks on a bike and already there's
>> noticeable overlap (toe can touch front tire when
>> wheel is turned at a certain angle) and wonder if
>> going to 175mm is asking for trouble.
>>
>> What did Merckx do, given he rode on 175mm cranks?
>>
>> Emanuel
>>
>>
>>
>>
>> =09
>>
>> =09
>> =09
>> _______________________________________________
>>
>
>
>
> =09
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