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New build on an old frame - seat post question

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New build on an old frame - seat post question

Old 12-11-11, 09:38 AM
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New build on an old frame - seat post question

I got hold of a 1970s Claude Butler frame and am in the process of building it up as my next commuter bike. It's a nice 531 frame, lovely lugwork, want to make a good job of it, etc. Just got it back from the powder coaters, now for assembly. I'll take it to the LBS to get the BB installed but am planning to do the rest myself.

I had the previous seat post measured; 27.2mm, so the calipers say (measured around the middle). I went and got a 27.2mm seat post to replace the rusty old steel one but it seems quite a bit too wide - it won't even start to go in. When I got the bike, there was about 17cm of seat tube showing above the frame. It wasn't until I removed it that I realised it was only 20cm long in total! On closer inspection, it also seems to taper to almost 25mm at the end. I wondered if the seat post clamp area could actually have been bent inward due to being over tightened around the tapering section of the seat tube.

What can I do about it? Should I continue to use smaller diameter seat posts, or should I somehow try and widen the clamp area back out? I've tried inserting the old seat post all the way in (with saddle attached). it does go all the way, past the 27.2mm middle section, and back out. It just closes back on itself when empty. One idea that crossed my mind was to put the old seat post right in, remove the saddle, and heat the end up under a flame causing it to expand... crazy?

RE. the rest of the bike, I've got all the bits including the wheelset (rear hub is a Sturmey Archer S3X fixed 3 speed), am excited to get this thing on the road...
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Old 12-11-11, 10:55 AM
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Apparently the "ears" and the slot in the seattube that clamp the seattube around the seatpost have been distorted by overtightening. Realign them and the new seatpost should fit. DO NOT use heat. You will destroy the paint and, if you overdo it, you could damage the brazing. If you are worried about doing this yourself, a knowledgeable bike shop or frame builder can correct the problem for you.
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Old 12-11-11, 11:04 AM
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Definately get it to accept the correct seat post for the frame.
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Old 12-11-11, 11:26 AM
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It might be good to measure the inside diameter of the frame partway down the tube to see what size it really is. Pop over to CT and you can borrow my telescope gauge and micrometer.

Also, post in Classic & Vintage with as much detailed frame info as possible, including pictures of the seat cluster, and someone there may know the correct size.
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Old 12-11-11, 12:40 PM
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HillRider - I did think heat was probably a bad idea, thanks for confirming I like my LBS, I'll let them sort it out.

CACycling - noted! Will do.

Homebrew01 - kind offer, I'd totally take you up on it if it weren't quite so far;

I'll definitely do more homework on the correct seat post size for this frame.

Cheers guys!

Hmmmmm lots more questions about other bits. Guess I'll be back when the time comes to put it all together.
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Old 12-11-11, 12:51 PM
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Originally Posted by MarkN
...1970s Claude Butler frame ...lovely lugwork, want to make a good job of it, etc. Just got it back from the powder coaters,... (rear hub is a Sturmey Archer S3X fixed 3 speed),...
Huh. Good luck with your project.

Maybe take the frame to a bike shop you trust, have them measure for a seatpost, order seatpost through them. That way, if it's the wrong size, on them to make it right instead of you guessing. If a rusty post came out, could very well need slight reaming just to clean things up.
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Old 12-11-11, 02:35 PM
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Beside the above suggestions check the condition of the seat tube interior; paint may have gotten inside the seat tube and reduced its size.
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Old 12-11-11, 08:05 PM
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Originally Posted by MarkN
Homebrew01 - kind offer, I'd totally take you up on it if it weren't quite so far;
I need to get over there & visit my dad before it's too late.
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