Correction here,
The typical 531 tube in the 78 catalog is a 5/10 tube in the non-butted section. But 4/10 tubes were available going way back in time I believe. And a reading of the Reynolds catalog makes no mention of the 531 SL tube being anything other than a thinner standard 531 tube. Its all marketing I say.
Mike Kone in Boulder CO
> Am I missing something here? Isn't 531 SL just a 531 tubset with very thinwall
\r?\n> tubing packaged as such by Reynolds?
\r?\n>
\r?\n> In the early days of French touring bikes (yep, there I go again), builders
\r?\n> built frames with 5/10 or even 4/10 tubing. In fact, they were using this lite
\r?\n> stuff even in the 30's. So while it was not labeled as such, the very light 531
\r?\n> tubes were available for many years before they were called SL.
\r?\n>
\r?\n> Mike Kone in Boulder CO
\r?\n>
\r?\n> -------------- Original message --------------
\r?\n>
\r?\n> >
\r?\n> > 531 SL, like other 531 sets, probably came with a few different choices
\r?\n> > of chainstay shapes - I don't remember. But I saw several SL bikes that
\r?\n> > broke, which all had a particular chainstay shape that I associated with
\r?\n> > 531 SL in my mind. These stays had a sort of flattened area for the
\r?\n> > tire clearance, making the cross-section close to a "D" there, instead
\r?\n> > of the more normal indent like Columbus used at the time, or the
\r?\n> > perfectly acceptable Reynolds round-oval-round or rapid taper styles.
\r?\n> > The ones I saw that broke numbered two or three, not a valid sample size
\r?\n> > but it made me suspicious, and they all broke where the flattened area
\r?\n> > transitioned to the round - the shape changed too abruptly and the
\r?\n> > crease was too sharp, in my opinion. Also being the weaker, non-heat
\r?\n> > treated steel made it harder to get away with less than perfect shaping
\r?\n> > of the tubes -- 753 in that shape might not have broken.
\r?\n> >
\r?\n> > Did any one else here notice this chainstay shape, and did it live a
\r?\n> > long, fruitful life or did it die young?
\r?\n> >
\r?\n> > To the poster who worried (back in the day) that 753 might be too stiff
\r?\n> > - it was in fact a bit less stiff than 531 SL. They did make some
\r?\n> > variety of wall thicknesses in 753, but even the heaviest of the
\r?\n> > commonly available 753 sets was lighter and less stiff than 531 SL.
\r?\n> > (Not counting tandem and off-road 753)
\r?\n> >
\r?\n> > Tubing specs for 531 SL and 753 as of 1978 can bee seen in these catalog
\r?\n> > scans:
\r?\n> > http://bulgier.net/
\r?\n> >
\r?\n> > or http://tinyurl.com/
\r?\n> > http://bulgier.net/
\r?\n> > or http://tinyurl.com/
\r?\n> >
\r?\n> > Note the thicknesses are given as gauge, where a larger number means a
\r?\n> > thinner wall. Sorry the text is so hard to read; I should have put them
\r?\n> > up at a higher resolution. In case you can't read it: All three choices
\r?\n> > shown for 753 are thinner than 531 SL in places, some tubes being the
\r?\n> > same thickness in both, and no tubes being thicker in 753.
\r?\n> >
\r?\n> > Mark Bulgier
\r?\n> > Seattle WA USA