Above: The main 531 sticker on a Raleigh Record Ace Frame (courtesy H Lloyd Cycles). This was unique to the RRA. However some Gillott frames have also been built using this same sticker
The main tubes of the Raleigh Record Ace frame are manufactured from 531 tubing.
The forks could be specified with round or “D” section 531 tubes. D section tubes were no longer available as an option after 1949.
Pips for rear rack, or pump braze ons could be specified by customer, as could the braze on for a Sturmey Archer boss for the control wire.
531 tubing- a brief history
531 is a seamless tubing made of Manganese Molybdenum, better than standard Cro-Mo, but time has caught up with it a little as the top tubes from Columbus and Reynolds have a higher UTS (ultimate tensile strength).
531 tubing in various forms has been around for over 60 years now. It was originally used in aircraft construction, then racing cars, motorbikes and most importantly for cycles.
In that time, as a tube set, it has notched up more Tour de France wins than any other tube set.
Originally plain gauge, it has over the years been available as:
* taper gauged,
* wafer thin,
* ovalized and even larger diameter in the centre of the tube than the ends.
It has also been used by the master builder Horace Bates in his ‘Cantiflex’ frames with perhaps the weirdest incarnation being the “Curly Stays” fitted to Hetchins and now some Bob Jackson cycles.
No other manufacturer of cycle tubing offered this kind of range and flexibility (and probably will never do so again) so 531 became THE tubing for custom build frames. Its availability in a dazzling array of shapes and sizes to the custom builder meant that elements could be picked and mixed to match all different rider combinations and purposes.
It can also be cold set (bent about) which meant that if the builder wanted to widen the rear width years after the frame had been made there is no problem, and no fancy construction techniques are required to build or repair it beyond the limit on brazing temperature.
The relatively low UTS compared with the newer tubes isn’t really a problem as the gauges need for touring are too thick to ever break even on a loaded bike, it only becomes a factor when the tube is drawn wafer thin then used by heavy riders, as in the past with 531 Professional.