It's been a long time... just over two months... even forgot the email address.. still thinking in French... but it's time to get back to the real world.
Howard Darr asked about the feasibility of converting a road frame into one for cyclo-cross purposes. Yes... it's been done many times.. and quite successfully too.
But it's not just a question of brake stirrup lengths and clearances under the fork crown and the rear brake bridge, although these are clearly extremely important factors. ig you are considering racing or even "rough-stuff" riding for pleasure, probably the most important factor to take into consideration is - ground clearance.
A purpose-designed and built cyclo-cross frame will have a bracket height built to take into consideration the type of terrain to be cycled across. Whereas the "standard" road bike will have a bottom-bracket height of around 10.75", most cross bikes will have a height of 11"/11.25" or even more. This extra height gives extra clearance for cranks and pedals, using "standard" length 170mm cranks. on a well-designed cross bike the chainstays are much nearer parallel to the ground than they are on a standard road bike. To magnify the difference just put two bikes one a "cross" and the other a 1940/50s European "massed start" bike side by side... and you will notice the difference immediately. The 40/50s bikes often had bracket heights of 10.25", with the chainstays ascending quite noticeably to the rear drop-outs.
The wide-spread use of cantilever brakes on "cross" bikes was both an acknowledgement of the generally superior and more rigid functioning of this type of brake, as it was of the fact that the builder was not restricted in placing the fork crown and the rear brake bridge by the length of the brake stirrup - hence he was free to build-in much larger clearances for all that mud and clag.
Hope this helped out a bit.
Norris Lockley.. in a direly miserable Settle, UK
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