internal diameter of 531 seat tubes

ScillySuffolk

Retro Guru
I recently read a post which detailed the above, but I can't find it now I want to.

Can anyone point me towards it? Alternatively, can you tell me if 531c ever came with a 26.4mm seat tube?

I seem to remember that the poster wrote that the top end 531 was either 27.2mm or 27.0mm.

Many thanks.
 
Thanks Tel.

So was "c" only available double butted, ie if it's 26.4mm (and therefore plain guage) it isn't "c".

I'm not a tube-snob or weight-weenie, but the frame is in original condition, with both the manufacturer's and 531c decals lacquered in place (ie apparently kosher) but it takes a 26.4mm seat post; so in my limited experience, something is not right.
 
If it has a 531c badge but doesn't take a 27.2mm seatpost I would certainly be suspect that it is genuine 531c. That's not to say that it never existed, strange things have happened over the years and I'm certainly no expert just talking from experience. Perhaps for example very early 531c took a 26.4....I do believe there was single butted tubing too which I do not know the diameter of (or the badge for that matter).

Are you measuring the size of the tube or the size of the seatpost that was in it?
 
ScillySuffolk":1rroiz76 said:
I recently read a post which detailed the above, but I can't find it now I want to.

Can anyone point me towards it?

Was you referring to this post:

sawston_vulcan":1rroiz76 said:
Could also be a Holdsworthy Claud Butler...need to ask the seller the seatpost size as that is indicative of the tubing...27.2mm or 27.0mm it will most probably be 531 DB but any less.....26.8mm 26.6mm or 26.4mm......then it is likely to be plain guage 531...will give a good ride but heavier......and i'm with Shaun.....the forks go with the frame but of little consequence if they are the originals....which might have perished in a crash etc.

from this thread? http://www.retrobike.co.uk/forum/viewtopic.php?t=210412
 
Yes, that's the one, thanks: it drives me mad when that happens!

It didn't come with a post and I was a bit surprised when I went to drop a NOS Selcof, that I had been saving, in and it didn't fit.

The tube isn't crushed or deformed so I put the calipers on it and got 26.4mm.

I've measured the external diameter at various points and have 28.7/8/9mm; the tube wall measures 2.5/6/7mm.

It's the frame I posted about yesterday. I'm more curious than I am concerned: it's a nice frame anyway and I paid a good price for it, but as I noted above all the decals seem original, which doesn't square with what the calipers are saying.
 
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