Reynolds 531 Magic Tubing

I would say that 725 is the nearest equivalent to 531c nowadays, certainly it makes lovely touring bikes in the hands of good designers (e.g. Hewitt, Spa).

Note that 531 is just an alloy, there were countless tubesets: 531db, 531SL, 531c, 531 ATB, 531 Magnum, 531ST, Tandem amongst others plus loose tubes (531DS) and versions in metric and imperial sizes. Add in whether the frame is well-designed and then the magic happens.

520 and 525 are identical, the difference is that 520 is sourced and made in Taiwan.
 
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Note that 531 is just an alloy,
I think Reynolds tubes are all alloys whatever the number, I heard that 531 is the proportion for the mix, how true this is I don't know. Chrome molybdenum manganese. You're right 725 is great My Thorn (Long gone) had it. Didn't know that about 520/525.
 
Yes, you are right, 531 is the approximate ratio. The important thing is that it's Manganese-Molybdenum not Cr-Mo and cannot be welded easily.
It was a super-high tech product when launched in the 1930s. Aircraft wing spars were made of it, notably the Hawker Hurricane. It was also used in racing car chassis in the 1950s.
 
The important thing is that it's Manganese-Molybdenum not Cr-Mo and cannot be welded easily.
I think there is no real equivalent to 531. It has probably been retired because of the welding properties, I guess. All modern Reynolds tubing is a form of chrome moly, judging from their info: https://www.reynoldstechnology.biz/materials/steel/s-520/

The feel of a frame, jufging from personal experience is in the tube diameters and wall thicknesses. I reckon a good builder will be able to tune a frame appropiately.
 
This is interesting.
The common wisdom of the internets suggests that the stiffer OD tubing does not ride as well as old-school small diameter tubing.
The same wisdom claims that 531st does not ride nearly as good as 531c because the former is thicker & stiffer.

Yet, 531ATB is even beefier than 531st, and Magnum has almost the same thickness as ATB, but should be stiffer due to larger diameters...

So in theory, based on Dr. Google's knowledge, you are riding one of the stiffest 531 tubesets bar the old non-butted ones, yet you're enjoying the ride 🤔
Must be something about them 531 stickers.

PS in regard to road bikes, my 531db, which later became 531c is a very sweet ride, but not the same league as butted Waltly titanium, with both bikes running the same 25mm tyres.
 
I was told in the early 2000s by a metal rep (531 was used in motor sport for tubular chassis) that reynolds stopped cycle 531, mainly due to swapping production to asia.....the quality became a problem. The replacement was partly to stop direct comparison between uk 531 and asia 531.... two sadly differing quality products.

I dont know if its true, but it does seem that most do not rate 520 etc as a " good" frame tubing choice. It is certainly strong, but so is gas pipe....
 

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