Cycling UK Forum

I know this is an old chestnut but... how do you cure an over tightened seat pin?

What has happened as a result?

Post has been crushed or is it stuck in the frame?

sorry for delay coming back:

the result is that that seat post drifts down or the saddle turns. It is my son's nice old Holdsworth 531 frame. I'm assuming he over tightened it. G

I had a similar problem with my old Holdsworth. In the end I discovered that the old seatpost that was on it had been shaved down over the years and was no longer fat enough to fit properly.
So buying a new seatpost which actually was the size written on it, rather than .2mm smaller did the trick.
As your son's seatpost has been slipping and twisting you may well be in the same position.

A bit of a clue was that the two sides of the cut out in the frame were touching each other when I tightened up the clamp!

garry: I'm not sure if I follow you. It's not over tightened as it's slipping: so what is the problem? I would suggest you check as meic suggests that the seat post is the correct diameter (use vernier caliper if necessary) and whether the cut outs have met in the middle. If all is well, I suggest that you check the bolt - we had a problem recently of a slipping seat post and found that the bolt was the wrong size - it wouldn't tighten any further.

I had a similiar issue and found the seat tube was oversized (It'd been fitted with a shim on manufacture, to reduce it from 31.8 to 27.2mm). I found the shim (Soft aluminium had worn), causing creaking/slippage

Thanks very much people. I will investigate these different avenues with laddo. G

I agree check the pin you are using is correct size (generally 27.2 mm for Reynolds 531 frame) .

(I did cure a similar problem on an old track bike by lightly knurling the bottom of the pin but the right size is better.)

Local bike shop should help, they generally drop a reamer in to clean the hole before fitting new post ,particularly relevant if the frame has been refinished or even new, framebulder should have done it as brazing may cause light distortion . (And occasionally tubes get put in upside down I am told, I had an issue with a Peugeot PRX10 and my mechanic said the seat tube was in upside down, not uncommon with old Peugeots apparently)

Paul Arnold

Thanks Paul, very helpful. G

Not sure if this is relevant but I broke the bolt on my seat post clamp when I overtightened it in the middle of nowhere because my seat kept slipping. I believe the clamp had stretched. Eventually my LBS replaced the clamp with one by Campi which is perfect (and the only Campi gear on my bike)

Garry Booth wrote:seat post drifts down or the saddle turns.

if that's the fault, my first attempt to cure it would be a coke or beer can shim. with care not to slice yourself, take strong scissors to a can and cut out a bit to wrap around the post. a 3" square ought to do it

I had a problem with a slipping seatpin once which turned out to be that the two-piece seat bolt (rather than threaded lug) arrangement was bottoming out in the middle before the cutout was. I removed a couple of threads worth off the end of the bolt and all was well with far less tightening torque applied.