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PostPosted: Sat Aug 10, 2013 12:31 pm 
Dirt Disciple

Joined: Thu Dec 17, 2009 1:40 am
Posts: 94
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.


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PostPosted: Sat Aug 10, 2013 12:37 pm 
Gold Trader
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Location: High on a hill above the Somerset Levels...
Ditto, same issue with a 531C Paul Milnes frame! I thought all 531 tubed frames were 27.2.... :?


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PostPosted: Sat Aug 10, 2013 1:30 pm 
Dirt Disciple

Joined: Fri Aug 02, 2013 7:35 pm
Posts: 45
Location: Dorset
You could try a 27.0 seatpost to see if this is a loose fit .


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PostPosted: Sat Aug 10, 2013 5:39 pm 
Old School Grand Master

Joined: Tue Oct 09, 2007 1:55 pm
Posts: 8202
Location: New Forest, UK
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.


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PostPosted: Sat Aug 10, 2013 6:14 pm 
Gold Trader
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Location: High on a hill above the Somerset Levels...
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...


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PostPosted: Sun Aug 11, 2013 4:21 am 
Gold Trader
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LikeClockwork wrote:
Ditto, same issue with a 531C Paul Milnes frame! I thought all 531 tubed frames were 27.2.... :?


some are 26.4mm IIRC


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PostPosted: Sun Aug 11, 2013 7:47 am 
King of the Skip Monkeys
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Location: Moomin Valley
531 is 'normally' smaller than 531c. So far, all of my various 531c frames have been 27.2 with 531 averaging around 26.8


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PostPosted: Sun Aug 11, 2013 10:38 am 
Retro Guru
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Joined: Mon Mar 26, 2012 5:21 pm
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Dead Rats wrote:
LikeClockwork wrote:
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.


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PostPosted: Sat Aug 17, 2013 1:37 pm 
Dirt Disciple

Joined: Thu Dec 17, 2009 1:40 am
Posts: 94
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.


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PostPosted: Sat Aug 17, 2013 3:47 pm 
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Joined: Sun May 16, 2010 9:15 pm
Posts: 343
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.


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