It appears that my little anecdote about Mercier's decision to drop Reynolds 531 tubing due in part to problems of splitting, as recounted to me by M Rigobert, lightweight cycles specialist of Annecy, has stirred up a bit of a hornet's nest.
Since posting it I have had a look through my 'Black Museum' - the sort of scrap corner where many framebuilders accumulate various horrors of frame-building. The Raleigh seamed head-tube is still in the bin alongside another crunched Raleigh 531DB touring frame whose tubes also show some evidence of being seamed.
Reynolds 531 is of course the name of a certain manganese-moly alloyed steel that was made into tubes. As most cyclists know the tube, it is usually but certainly not always DB - double-butted, a special process invented by Rynolds to make lighter tubes that retained many of their original physical properties. Additionalaly I think that we, particularly frame-builders, have assumed it is always solid-drawn ie seamless not seamed and simillarly we have assumed that a solid-drawn tube is far better and reliable than a seamed one - not without good reason.
In the early 80s I met up with a Parisien frame-builder , AMR, who introduced me to a French brand of tubes called CAMUS. This firm produced the first full set of tubes designed specifically for low-profile frames, in that the top-tube was banana-shaped, and the seat-tube had the double compound curve, fork blades and stays being all aero-profile, on the European market.
The tubes were excellently presented, very light..and had excellent working properties but turned out to be seamed ones not seamless and not DB. I used dozens of these aero curved-tube sets..and many other standard tubing sets made by CAMUS...and never had a single problem...not a single split or crack. Some riders preferred the tubes to the extralight sets produced by Columbus.
Examining the interior walls of the tubes would yield no indication that the tubes were seamed - there being neither a ridge nor a discoloured line to indicate the butt-weld. Perhaps the most surprising aspect of the tubes is that the PG seat tube that had a wall thickness of 0.8mm could be bent in the compound curve without any distortion or 'crinkling' of the tube..
Unfortunately CAMUS tubing was never a strong enough company to survive the cycle industry's move into aluminium. The various series were extremely versatile and very widely used by the artisan builders of central and northern France.
Norris Lockley
Settle UK