What's up with the framebuilders on the List? Don't you want to reveal y our trade secrets?
As no one has helped John Redman to understand the profound mysteries of racing frame design, I thought that I might venture forth and try to provi de a little insight.
Your suggestion of 73// parallel is not a bad starting point and, if you had an inside leg measurement of around 33 or 34", coupled to a torso that is shorter as a proportion to the body as a whole, you could do worse than to ride a 23"/57cms frame with 73//73 angles. Eddy Merckx was quoted some years ago that he took the 73//73 configuration as a starting point for his frames, which varied between the sizes of 57 and 58.5 cms depending on the race, the terrain etc. However for massed start racing this design is very adaptable but needs to be varied if the rider is to tackle time-trials, cr iteriums, or stages with very sinuous descents etc.etc.
In the 50s a 72//72 configration was most common linked to a rear triang le length of 42, 43 or even 44 cms. , the bracket height being usually arou nd 10.25 or 10.375" (260 to 263mms) During the 60s these angles changed wit h 73//73 becoming more popular until they were standard almost in the70s li nked to a slightly higher bracket. The late 70s and the 80s saw the "stiffe r" italian designs making an impact and in the UK ;74//74 was very popular, the frames often doubling up for massed start racing and time-trials. At the same time the bracket height seemed to creep up to an all-purpose 1 0.75 (273mms), while the rear triangle became almost a standard 40cms. Ofte n such head angles on smaller frames led to considerable overlap of the toe -clips and the front wheel.. In an ideal world, on smaller road racing fram es the head angle should become shallower as the seat angle steepens in ord er to provide a shorter top-tube while still avoiding front end overlap. Th e opposite should be applied to larger frames.
About 1980 TCT, the French manufacturer of carbon-tubed bonded lugged fr ames developed a type of geometry that was almost universally adopted by ot her continental manufacturers and many craftsmen builders. Because TCT/TVT had more successes in races such as the Tour de France than any other manuf acturer ( frames often bore the transfers of Pinarello, LOOK, Colnago, Vitu s etc etc) it was assumed that this company had developed the ultimate geom etrical formula for road racing frames.
The design philosophy was simple - just keep it simple., TCT/TVT used ju st two seat angles throughout the range of frames from 49 cms up to 62cms.. For the frames up to about 54cms the seat angle would be 75degrees and 30 minutes and beyond that 74.30. Head angles varied very little too, with 73 being common up to around 57cms and 73,30 thereafter. front end clearances ranged from 585mms on the 49cm frame up to 603 on the 62cms frame, with 595 /600 being the most common, There was never a problem with overlap. Rear tr iangle was 40cms..possible due to steeper seat angles, and bracket height w as a standard 270 mms. TVT did offer a made to measure service for th ose riders requiring slacker angles. Lemond wanted a longer top-tube and us ed a 72 degree seat angle.
I hope that this short resume will give you a litle insight, John, but t o cover the permutations of time-trials, criterium frames etc it would be t he work of a Masters Degree thesis.
Time permitting I will try to dig out the frame measurements for Hinault , Merckx, Thevenet, Kuiper, Van Impe , Poulidor, and Zottemelk.
Norris Lockley, Settle UK
Norris Lockley
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