Re: [CR] Measuring bike frame angles

Ken Freeman wrote: "I am amazed that Carlton offerred such options in frame ordering, back in the day. Seat angle is driven primariily by leg proportion, the rider's need for a certain front/back saddle position, and consideration of weight distribution. The head angle is much more connected to performance, toe clearance, upper body comfort, and handling of the bike - rather more complex.

"Short rake Russ" certainly suggests small rake, which (depending on head angle) could result in a larger amount of trail and some toeclip overlap. Of course, this also is related to the amount of top tube length that is not behind the BB."

I have had some correspondence off-list with Fred Rednor, and my latest reply may be of interest, in view of Ken's comments regarding the options in frame ordering:

"If you go to http://www.classiclightweights.co.uk/bikes/harrison-super-circuit-rb.html you'll see another of my bikes. In the 1938 R O Harrison catalogue, the angles are listed as 75 head/73 seat; in the 1939 Catalogue, 74/72. For other models in the 1939 catalogue, the angles listed range from 70/70 (Club Tourer) through 71/71 (Club), 72/70 (Meteor grass track/time trial) model 74/70 (Madison 6-Day track model), 73/71 (Omnium cement, grass and cinder track model; Lyta ultra-lightweight model and Continental model). However, like many of the small builders, R O Harrison would build the various models to the customer's requirements, within reason."

This suggests that at that time, the frame angles were linked to the purpose for which the machine was required, rather than the customer's own characteristics. However, the builders must have been able to, or they wouldn't have stayed in business too long.

I wonder how critical the dimensions quoted by Ken are; I ride frames varying from 22" to 24" centre to top, with various top tube lengths and various frame angles, because in the old bikes, I have to take what comes along, within reason. As long as I have the seat height and handlebar reach right, I find them equally comfortable from the point of view of my position on the bike. On the other hand, for example, Gillott offered two variations of their Taper-Tube model for the tall rider in their 1953 catalogue:

Specification (A) for "The man with the long thigh [who] needs to sit back...": head 73/seat70, top tube 23.5", fork rake 2.75", rear triangle 18", wheelbase 41.75", bottom bracket height 10.75" with 27" wheels.

Specification (B) "For racing and where a more forward specification is necessary...": head 72/seat72, top tube 23", fork rake 2.5", rear triangle 17.5", wheelbase 41.5", bottom bracket height 10.5" with 27" wheels.

My own Gillott Taper Tube is to Specification (A), and although I'm 5' 10", and of average dimensions, I find it comfortable. Do such small differences in dimension really make that much difference? Maybe I'm relying on the flexibility of the human frame in adjusting to varying dimensions, and am not obtaining maximum efficiency, but I genuinely can't tell the difference, in terms of comfort.

As far as the small makers of high-class lightweights are concerned, I suspect that the interest in frame angles developed during the latter half of the 30s, when "upright" frames became fashionable. Before that time, I have found no mention of angles as a criterion in framebuilding, especially from the customer's point of view, either in contemporary catalogues or in cycling publications I've read. Before this time, frame size and weight seem to have been more of interest; during the 20's and early 30's, the fashion was for very small frames, with a long length of seat post protruding, especially for tall riders. Plus ca change...

Neil Foddering
Weymouth, Dorset, England