531 Competion seat post diameter

[unicanitor]

I recently acquired a Hewitt track bike thanks to a huge amount of help from fellow forum member Drystonepaul.

I estimate the frame to be mid 90's, 531 Competition and came with a 27.2 seat post. Is this the correct size does anyone know? It seems incredibly tight and i can't find anything conclusive through online searches, opinions varying right down to 26.8

The original picture of the bike showed very little seat post inserted in the frame - i put that down to the previous owners set up as the stem was similarly high, i really need the seat post inserted beyond the minimum level which equates to around 4". Is this a case of copious amount of grease and perseverance or does this tube set take a smaller post?

Thanks in advance for any help.

 

[LikeClockwork]

Ditto, same issue with a 531C Paul Milnes frame! I thought all 531 tubed frames were 27.2.... :?

 

[JohnM]

You could try a 27.0 seatpost to see if this is a loose fit .

 

[hamster]

Nominal for an unbuilt tube is 27.4mm. Usually brazing distorts a little ovalising it to 27.2 or so. Your seatpost might well be oversize, it is not uncommon.

 

[LikeClockwork]

For what it's worth, I gave the seat tube on mine a really good clean out, and ran a needle file around it and the slot to de-bur it. With some grease on the post, 27.2 is no longer a problem...

 

[Dead Rats]

Ditto, same issue with a 531C Paul Milnes frame! I thought all 531 tubed frames were 27.2.... :?

some are 26.4mm IIRC

 

[legrandefromage]

531 is 'normally' smaller than 531c. So far, all of my various 531c frames have been 27.2 with 531 averaging around 26.8

 

[ScillySuffolk]

Ditto, same issue with a 531C Paul Milnes frame! I thought all 531 tubed frames were 27.2.... :?

some are 26.4mm IIRC

My Orbit America is 531C and 26.4mm.

I had my doubts originally, but it's all original (decals under lacquer) and I can't imagine Orbit doing anything underhand.

I did e-mail them, but didn't get a reply.

However, I do know that with the many flavours of 531, it's not exclusively 27.2mm.

 

[unicanitor]

I had a play around with this, this morning - tried two different 27.2 posts on the off chance one may be a little oversized - nothing doing

I've given as good an inspection of the seat tube as i can and it looks and feels as smooth as anything inside. Tried the LBS with their sizing post and they confirmed......yep, 27.2

I can only assume the top of the seat tube is slightly ovalised but i just can't get the 27.2 anywhere near it let alone where i need it to be.

 

[American Friend]

The seat tube may have been deformed by a previous owner over-tightening the seat tube cluster with an undersized seatpost inserted. Any decent framebuilder can ream it out for you for a few quid if it was indeed originally 27.2mm.