In and amongst all the Contris on this topic lays the answer to the ques tion.
In the 50s and 60s reynolds 531 DB tubing could be obtained in a very of gauges and weights to cater better for the variety of sizes of frames that builders were called upon to put together. Possibly as a result of th e decline in interest in cycling when folk became more affluent and bought other means of transport, Reynolds removed to a very large extent the avail ablity of these tube sets.
I think it was in the mid-70s,possibly the early 70s when reynolds reint roduced lighter gauges of 531DB, but on that occasion they called it 531 SL . I think that Doug Fattic must have come across the tubes at Ellis_briggs because I know that they used it quite regularly, much to the displeasure o f Jack Briggs who once told me that the company had had more broken frames using that tube set than with all the other frames put together.
As Toni stated, the main problem was the drive side chainstay . The mann er in which Reynolds had pressed in a "flat"in the region of the inner chai nring, tended to produce a stress-riser which in turn led to the stay crack ing. Jack said that EVERY 531 SL frame made by Briggs had cracked at the sa me point. There was also some concern about the gauge of the seat-stays and chain-stays as the frames tended to whip around more than was required.
Not to admit defeat, Reynolds built on the "SL" theme by introducing the 531 Pro set. This was very similar in the main triangle to the 531 SL, as far as I can recall, but the chainstay indentation was changed, and the sea t-stays became bi-conical. Tjhere might have been an option for standard st raight taper ones, but Reynolds were trying to capture a more "continental" look to the tube set.
Once again history almost repeated itself, as the Pro tube set also had some in-built problems. Although the set performed far better than "SL" set .particularly in rear triangle stability and effective cornering, the bi-co nical stays could cause problems when used in certain applications.
Over the winter period in the UK the sport of cyclo-cross is very popula r, whereby as you will no doubt know, the rider rides his bike along the ro ads and rideable paths but often has to heft the machine over his shoulder and carry it when the going gets really rough or the slopes too steep to ri de. Therefore many riders siought frames that were lighter than the standar d 531DB..and 531 Pro became popular. However it was soon discovered that th e constant minute flexing of the cantilever studs on the seat-stays under b raking forces, was causing the stays to develop hairline cracks at the poin t where the studs were brazed in place.
I think it was Wes Mason who first drew my attention to this phenomenon. He had been commissioned to build all the frames for a leading Leeds-based club cyclo-cross team, I think it was the Seacroft Wheelers. Not long into the season riders started complaining about irregular braking and creaking noises . When Wes investigated he found the cracks.
The problem arose due to Reynolds having reduced the gauge of the metal at the point where the studs were brazed, in order to "blow out" the stay t o its fattest point in the bi-conical pattern. If that fat point just happe ned to coincide with the point at which the stud was brazed on, then one co uld eventually expect a broken stay. On the other hand Columbus always main tained a constant wall thickness for their bi-conical stays. As a result of this experience all our subsequent 531Pro "cross" frames and small l ightweight touring machines were built with the heavier and thicker 531 DB seat-stays.
True to form, Reynolds built on adversity, scrapped the 531 Pro set and replaced it with the 653 one, complete with sexyily shaded transfers. I thi nk that this set had 531DB (lighter gauge) main tubes.. possibly fork blade s as well..but 753 rear stays.
About the time of the 531 Pro cyclo-cross framsets, the other popular ve ry light frameset was the Speedwell titanium one. Thank goodness that never appeared, as far as I know, with canti bosses TIGGed on the stays.
Norris Lockley..Settle UK
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