Bicycle Mechanics - installing seatpost into new frame - how much pressure?
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05-20-07, 06:33 PM
It is a 27.2 mm alloy seatpost and a steel frame - True Temper AVR. It's an older frame but NOS - I don't think a seatpost has ever been installed.
First few inches were tough but ok. But, I'm still a couple inches from the min insertion line and it's become almost impossible to continue moving the seatpost into the seattube.
How much effort should I put into making this work, or is it more likely that this is a 27.0 seatpost?
05-20-07, 06:39 PM
It shouldn't be that hard. My suggestion is to remove the seatpost and find somebody who can ball hone out your seat tube.
05-20-07, 10:59 PM
I have to think your older steel frame was designed for a 27.0 seatpost. Sorry.
05-21-07, 07:17 AM
Are you 100% sure of the correct size required? LBS owner told me that there are 40 different seapost sizes from over the years. Even if available the mfgs. specs can be misleading. Had a Jamis Eclipse that the spec sheet showed was a 27.2. Turned out to be a 1998 frame which took a 26.8. If your LBS has a seatpost sizing device use it or a micrometer would be helpful. Micrometer is the second tool I purchased and have used it 100s of times to make sure things are the right size.
all true, but do not discount the advice of the first response. Sometimes a "correctly" sized seatpost will just be too darn tight. A light buffing of the tube or post might cure it.
Just get a 27.0 and move on. The clamp is supposed to provide the force required to hold the seatpost in place, not the seat tube.
05-21-07, 08:39 AM
I think you've probably got a frame intended for a 27.2 post and it so happens you have a tight fit. Sanding or having the seat tube cleaned up at a bike shop would probably be the way to go. If you can, find another 27.2 post and see if it fits any better, there's variation from post to post, too. If the seat tube were intended for 27.0, I doubt you'd have gotten the 27.2 in as far as you have. .2mm doesn't sound like much, but in seatpost sizing, it's quite a difference. And I'd definitely rather have a very snug post than one that's loose-
Oh come on! Just get yourself to any decent bike shop nearby and try a 27.0. Can't take more than an hour. Probably less time than you'd end up spending getting the damn thing out again some time in the future...
05-21-07, 09:29 AM
This is a non issue, get a digital caliper, measure seatttube and measure the seatpost.
05-21-07, 09:48 AM
Guys, I appreciate the responses.
I am a pretty strong guy, and I almost sprained my wrist trying to get the thing in last night (using an old saddle as a lever, plenty of grease, blah blah blah). This morning I got up, my wrist felt better, and I almost shattered my back trying to get the thing out.
That said, I was able to get the thing in about 4 inches. Measuring carefully with a ruler - I do believe it is possible to eyeball, with a good ruler, within .2 or .3 mm - the seat tube is definitely 27.0 or 27.2, and not 26.8.
I will go with 27.0.
05-21-07, 10:14 AM
I had the same kind of problem with my other (old) bike. Well almost the same problem, my new post was to small, so I ended up tightening the frame far more than I should have. If i remember correctly the old seatpost was 27.0 and the new was measured to fit that exact size.
I think there's just something with either measuring errors by manufacturers or thermal wear. Specially if you store your bike outside or in cold places off-season the frame might, over time get modified. However this is just my own theory (too far fetched?).
Anyway, as i think some already suggested, I'd just grind the seatpost down a bit. If it's coated with something that, if removed would severely damage integrity I'd try to grind the inner-side of the frame.
05-21-07, 10:46 AM
A new frame should be reamed to insure proper fitting.
05-21-07, 10:47 AM
I'd just grind the seatpost down a bit. If it's coated with something that, if removed would severely damage integrity I'd try to grind the inner-side of the frame.
I would grind the steel frame before the aluminum seatpost.
But, I will go one size smaller first and see how that works out.
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