Reynolds 531c/sl/? frame weight.

[J0ckieboy]

Is there anyone with the information to help me discover if my light, steel, '70s frame is Reynolds 531c (competition); Reynolds 531sl (super light) or some other lightweight steel? (I don't know much about CIOCC frames but could it in fact be one of those?)
I had the frame stripped and repainted a few years ago. Based on the age and origin (see below) of the frame, I am making the presumption that it is made of something from Reynolds contemporary tube selection. The forks, on the other hand, have a 'Columbus' stamp on the stearer tube - I therefore presume the forks are made of some Columbus steel variety.

The frame is a 'Roy Thame' from the mid-1970s.
The frame size is 600mm c-t.
Originally the frame did not have cable guides on the top tube and gear cable stops on the down tube, but I had them added a while ago.
I've included a picture of the recently painted frame and the forks on a digital kitchen scale. The frame weighed in at 1833 grams. The forks weighed in at 734 grams.
Regular Reynolds 531 frames of similar size seem to be near 3000 grams, hence my suspicion that this frame is made with something lighter.

I would appreciate any help I can get uncovering this mystery.

 

[hamster]

Looks about right for a 531c frame, although your looks a large size.

 

[glpinxit]

My Raleigh 58.5cm frame in 753 is 1800g and the matching forks are 670g. My 58cm 531c frame is 2000g. All weights are painted.

 

[J0ckieboy]

Thanks 'hamster' and 'glpinxit'.
I've already 'cold set' the frame for a modern width hub so it is definitely not Reynolds 753 because it can't be 'cold set'.

glpinxit - based on your frame, I have a suspicion that my 60cm frame would appear to be too light for 531c.

 

[hamster]

I think you are right, it's not stock 531c. For a biggie it looks on the light side. However I though 531SL was the same as 531Pro (just a rename) and Pro used 753 stays - but you managed to cold set it. As it's from a custom builder it may have been from the loose tube option of 531. For example, the seat tube with the longer 280mm butt.

This may help:

On the other hand, as it has a Columbus steerer, maybe it's a cool frame made from mixed tubes from various suppliers.

 

[J0ckieboy]

I was thinking 531p (professional) after a little more research but if you (hamster) are correct about the 753 stays then it can't be. I have not been able to find any information about when 531p was introduced. Does anyone watching have a clue?

 

[Midlife]

There was deffo Pro in 1982, SL came about in about 1976 IIRC.

There was a lot of mixing and matching going on back then, Reynolds relented in the end and brough out a DS (Designer Select) decal >)

 

[pigman]

...so it is definitely not Reynolds 753 because it can't be 'cold set'.

sorry for the idiot question, but why can't it be cold set? Is it that stiff, it won't bend. Genuine question, I've never owned 753.

 

[J0ckieboy]

I believe that the heat treating the 753 tubes underwent made the tubes very stiff and perhaps too brittle to be cold set.

 

[hamster]

753 was simply too stiff - the stuff just sprung back.

Designer Select was the label for a mix-and-match tube set, only given to a few engineering-led builders such as Tony Oliver.