I've spent a good bit of my free time over the last few days searching the internet trying to understand exactly how the Reynolds 653 tube set was made.
I've found this Reynolds Constructor's Guide which lists the dimensions
https://postimg.cc/image/4m8eh9gmt/
And on BF there is this quote from @
Scooper;
Reynolds 653 is an odd duck. The stays are 753, but the main frame tubes and fork blades are 531. So, the seat tube is 531 (which is not heat treated), but the seat stays at the seat cluster are 753 which is heat treated.
Copied from another forum FWIW:
Reynolds 653 History
Thanks Jim. Reynolds have sent me a helpful reply so don't spend any more time on this one on my account. I'll tell you what they said as it's interesting and other folk might appreciate it too. In essence, 653 was invented following feedback from Eddy Merckx that a pure 753 frame was too harsh for certain stages. So Reynolds produced a 653 tubeset which combined 753 stays with 531 main tubes and forks. Not any old 531 though, but an even thinner gauge than usual - just for use in the 653 set. Eddy and other riders were very pleased with the result, which combined a light, ultra-stiff and efficient transmission with a more forgiving and comfy ride. Nowadays when folks are after a similar ride builders use 725 stays and usually 631 for all other tubes. I heard it from the horse's mouth.
"Cold drawn" has nothing to do with whether the tubes are heat treated or not; it's simply the term used to describe drawing the tubing through dies and piercing with mandrels to get the tubing to the specified wall thickness and butting.
So this got me thinking. Given Reynolds 753 is made from the same alloy as 531 that is then drawn thinner and heat treated and the 653 main tubes are made from 531 that has been drawn thinner but not heat treated. And the dimensions of the tubes in a 753 set are the same as the tubes in a 653 set. Isn't this the same as saying that 653 is just a 753 tube set where the main tubes have not heat treated? Am I off base on this one?
For some reson there is very little definitive information on Reynolds 653 anywhere online.
I also wonder if the Eddy Merckx connection is real or legend given Eddy retired in 1977 and Reynolds 653 hit the market a full 10 years later around 1987. Unless he was concerned about other racers that bought his frames.