"September 11, 20167:58 AM
Thank you for your kind comments. I don’t know all these details but will try to help where I can. And as I found out myself, sometimes even within Reynolds we get different answers.
Because of the initial development of the manganese moly steel (cold work=531) and then as a heat-treated version 753, followed by the comments from Eddy Merckx that he preferred a “softer” main triangle after he tried the first 753 sets, this led to the 531 front/753 rear which was also used in later years (e.g. by Indurain ~ 1990).
When 631/853 air hardening steel was developed from 1993 onwards, this replaced the Mn-Mo steel usage, and we started using more Cr-Mo (under our 525/725 brands) for practical reasons including availability, along with 631/853.
So – the initial 653 would have been 531 front, 753 rear.
Then, as we phased out high volume 531 and reduced the raw material range, we would have kept the 653 concept alive by using 725 stays. Note that from a technical point of the view, the stiffness and strength of a 531/753 and 531/725 combination would be very similar if the dimensions were the same.
At present, for most builders we still make a (very) limited range of 531 for a front triangle, but we have a reasonable range of 725 stays. So if a current customer wanted the “feel” of 653, they could use that 531 option (or from the large range of 631), combined with heat treated 725 stays.
I hope this answers the query?
Reynolds Technology Ltd"