seatpost very tight fit
03-03-17, 08:01 PM
#1
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seatpost very tight fit
Hey so I found a seatpost and put it into a bike. But it was very hard to get it in.
The frane takes a 27.2 mm and im not sure what size the seatpost is. If it was to big would I be able to slide it in very stiff or would it just not go in at all.
Its so stiff I was only able to get it about 1/3 to 1/2 down.
Does this sound like ita the wrong size or just very stiff?
The frane takes a 27.2 mm and im not sure what size the seatpost is. If it was to big would I be able to slide it in very stiff or would it just not go in at all.
Its so stiff I was only able to get it about 1/3 to 1/2 down.
Does this sound like ita the wrong size or just very stiff?
03-03-17, 08:16 PM
#2
Calamari Marionette Ph.D
All seat posts are "stiff". Some fit tightly and some fit loosely, but they are all "Stiff".
Did you grease it?
Did you grease it?
03-03-17, 08:28 PM
#3
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Does the seatpost have any inscribed numbers that might be the diameter?
If not, best bet would be to take some calipers and measure both so you know both seatpost diameter and seat tube inner diameter.
If there's any gunk or corrosion on the inside of the seat tube, that can prevent the seatpost from being fully seated. A bike shop can use a seat tube reamer and clean it out for you.
If not, best bet would be to take some calipers and measure both so you know both seatpost diameter and seat tube inner diameter.
If there's any gunk or corrosion on the inside of the seat tube, that can prevent the seatpost from being fully seated. A bike shop can use a seat tube reamer and clean it out for you.
03-03-17, 08:37 PM
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I'd check to see if either the seat post or the bike frame's seat tube were bent. I'd also check the inside of the seat tube for obstructions. If you can get it in 1/3 of the way I'd have to think that the seatpost was the right size.
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03-03-17, 09:18 PM
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Originally Posted by flik9999
The frane takes a 27.2 mm and im not sure what size the seatpost is. If it was to big would I be able to slide it in very stiff or would it just not go in at all.
As bargainguy noted, if the seat tube is rusty or dirty inside or distorted, the fit could be very tight even with the right size seat post.
03-03-17, 11:43 PM
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Originally Posted by flik9999
if it is the next size up 27.4 and its rammed in is that safe?
03-04-17, 02:49 AM
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Originally Posted by peugeot mongrel
If you force a 27.4 in a 27.2 it will freeze up later and it will become one of those horror story's of a stuck seat post.
03-04-17, 08:25 AM
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Originally Posted by Altimis
Its probably cracks first though if you actually forced it
03-04-17, 08:51 AM
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Could the post just be too long? My Cannondale seat tube narrows after a certain distance. I had to shorten a post so that my saddle could sit a bit lower.
03-04-17, 11:09 AM
#11
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A perfect fit was attained in the process of taking my 27.0 RB1 seat tube , to 27.2, by having the seat post in hand,and using an adjustable reamer
to shave out just enough, ID until the post fit , and quitting..
a shop I worked in, used to get out a ball burnisher ( It looks like a grape cluster ), chucked up in a Drill-motor. and running it into the seat tube
of every new bike as we were assembling it. for a second. de burring the factory ream job.
...
to shave out just enough, ID until the post fit , and quitting..
a shop I worked in, used to get out a ball burnisher ( It looks like a grape cluster ), chucked up in a Drill-motor. and running it into the seat tube
of every new bike as we were assembling it. for a second. de burring the factory ream job.
...
03-04-17, 03:18 PM
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Seat post fit is based on both the ID of the seat tube below the lug/joint area and the fit at the clamp. Note I didn't say "the ID at the clamp" The clamp insides are often not very round, distortion from heat being a common cause although other after manufacturing causes can also be present. The seat tube ID below the joint (and therefore away from any heat distortion) is usually the max post diameter that will work. Smaller post diameters might be needed to fit within the clamping portion. I suggest a lot of care and consideration before taking a reamer to a seat tube, once metal comes off it usually is gone forever and where that metal is removed is not always where it seems that it should be from. I have heard of seat tube wall being tragically thinned to a point of failure. The tool operator was watching the post fit in the clamped portion and not what was going on below. Honing with the common flex hones won't remove hardly any metal but will reduce down any burrs. I would work a tight clamp area first with mechanical methods then metal removing ones. Andy
