Chuck Schmidt wrote:
>Once again Jan... I never said tread was of no concern!
and
>I said that the small tread difference between a steel crank and an
>aluminum crank in the early fifties was not why the pros only used
>aluminum cranks for mountain stages and steel cranks for the rest of
>the stages in the Tour de France.
>
>I find your conclusion that difference in tread was the factor, and
>not the fact that aluminum cranks were unproven in pro racing in the
>early 1950s, baffling in the extreme.
We agree that the racers considered a difference in tread (Q factor) of 7 mm between the first generation Campagnolo Record cranks* and the 1960s model significant. (According to P. Delay, the chief mechanic of the Tour de France in Le Cycle, tread width was the reason Campagnolo re-designed the cranks.)
Yet you don't think a difference in tread between aluminum and steel cranks of 14-19 mm** - more than twice as much as the "significant" difference noted above - had any bearing on the decision of which cranks racers used.
Your assertion that the European pro racers were concerned about the cranks breaking would make sense if they always used steel cranks. However, a number of pros (but of course, not all) used aluminum cranks on mountain stages, where riding out of the saddle and sustained high power outputs will stress the cranks most. (If you are going to break a crank, it will be in the mountains!)
Consider that switching cranks between stages also required switching the bottom bracket (square-taper vs. cottered). This was not a trivial thing to do. I believe the consistent use of aluminum cranks for the mountains and steel cranks for the flats cannot be explained with a fear of cranks breaking. I propose that the well-documented concern about tread width (Q factor) provides an explanation that is consistent with the observations.
Professional racing bikes by the 1940s used many aluminum parts, including crucial components such as brakes and handlebars (Philippe Professionel, Ambrosio and other brands were common). I do not think there was a general fear of aluminum among the European professionals.
Of course, I am only talking about European professionals here.
British clubmen may have had other concerns. In the 1940s and 1950s,
the influence of European pro racing on the British scene probably
was much less pronounced than it was from the 1960s onward, when
British riders began to emulate British professionals racing in
Europe.
>I think if you are looking to me for heavily researched and highly
>academic articles to publish in Bicycle Quarterly you're talking to
>the wrong guy. I'm certainly not qualified and besides, it takes
>valuable time away from riding my beloved vintage bikes.
Yet you have no problems claiming that those who do the research are wrong.
Jan Heine Editor Bicycle Quarterly 140 Lakeside Ave #C Seattle WA 98122 http://www.bikequarterly.com
* The tread of a 1960 Cinelli S.C. with first-generation Campagnolo cranks (1958 model) is 139 mm. The tread of a 1965 Cinelli S.C. with 1965 Campagnolo cranks is 132 mm. The early cranks themselves are 3 mm thicker each than the later ones (15 vs. 12 mm).
** A 1957 Cinelli S.C. with cottered Magistroni steel cranks has a tread of 120 mm. A typical Stronglight 49D crank with double chainrings has a tread of between 134 and 137 mm. The first-generation Campagnolo was a tad wider than that (see above).
Tread usually is measured over the pedal mating surfaces of the crank, not the pedal center. Even with pedals of different width, most racers place their feet close to the crankarms.