Queries about the suitability of this particular tubing set crop up on a re gular basis on the List, either rehgarding its use for frames for heavier r iders or about some of the faults it was supposed to , and in certain sense s, did actually have.
It should be remembered that the tubing had been about in the 50s, when it was just one of the various gauges of the standard 531 DB, that were availa ble to help build lighter frames. I don't recall there being any restrictio n on or suggestion of a recommended maximum weight in those days. Indeed I remember top-builders such a Pat Skeates, Clive Stuart, Hilton Wrigley usin g the lighter tubes for frames as large as 24" - some of my clubmates rode these sizes. but only for fast road bikes, and not touring or track machine s.
The metalurgy of the tube ie the alloying elements are the same as those fo r the standard 531 DB...and no special care needed to be exercised, unlik e with 753 that emerged later, which had a different metalurgy. I remember talking to the Reynolds representative when the Series 531 SL was launched in the mid-70s, and recall that he urged the use of silver-solders rather t han silicon brazing alloys, in order to limit the heat input required. Howe ver this recommendation was due to the use of finer gauged tubes, not to al loying elements. It should be remembered also, that when the lighter gauge 531 DBs were in u se in the 50s, many builders were using different types of heat sources and gas mixtures. The age of the ubiquitous oxy-acetylene torch had not really dawned. In those days I was using coal (town gas) and compressed air. This gave a much larger, softer and less hot flame. The large flame actually en veloped the whole of a lugged joint with what we called a brush flame. It w as easy, but took longer, to heat the whole joint area to the same temperat ure without any fear whatsoever of over-heating or burning the tubing..resu lting in the brazing alloy running very freely throughout the joint.
Reynolds 531 SL got itself a bad name when frames started cracking on the c hainstays.. This was not due to any problem with the steel per se, but to t he manner in which Reynolds had put the dented area, adjacent to the poin t where the chainring would spin. Additonally, the gauge of the seat stay s and, I believe of the chainstays, was reduced. This lack of stiffmess gav e rise to the rear of the frame flexing under load.
When the set re-emerged as 531 Pro, with slight reworking of seat=stay se ctions, and indentations of the chainstays, the flexing had not been remove d sufficiently..which led in turn to 653, in which the rear end stays were made up of 753 components.. The problem was then resolved.
However the Peugeot Pro team used 531 SL frames with great success in the l ate 70s. Perhaps flex and stiffness are all relative terms and open to i ndividual interpretation.
Norris Lockley ...Settle UK