Brommie - slipping seat post

[Yellow Fang]

Took it into the shop at lunchtime. First, he said the clamp only appeared to be tight because the bolt needed oil. After lubricating it, he said that actually the cam was worn down on the clamp, so it was not actually applying much pressure on the post. My Brommie is an older model, with the older version of clamp. However, he had a stash of 2nd hand clamps, fitted one, and charged me £2.

 

[Milkfloat]

charged me £2.

And people say Brommie ownership is expensive.

 

[Kell]

I had the same problem on day 1. Solved by tightening the hex nut. Are you sure you have tried this properly?

I tried this with mine and it helped, but didn't prevent it from happening.

I've since loosened it after scuffing the post with sandpaper as I've read it can distort the frame if too tight. and I've had no bother.

 

[Yellow Fang]

No, I don't think the new clamp sorted it. Next stop: sanding the post, although I don't like the idea of that. Then a second seat post clamp, then friction paste.

 

[srw]

I find that over time the clamp gradually gets less effective at supporting my prodigious weight. Tightening the nut slightly (less than a quarter of a turn) is all that's required - I vaguely remember reading somewhere that over-tightening the nut will wreck a Brompton clamp.

To the OP - find a position where the clamp slips, and then try some very small adjustments.

 

[Yellow Fang]

Still having problems. Bought a QR 31.8mm seat clamp, but that did not work because even loose, it would not slip down the post very easily. Maybe I should get the next size up. I notice you can buy replacement seatpost sleaves and the rubberized glue, but it looks like a tricky job to get the old one out. I notice the sleeve is thinner one side than the other. I wonder whether it is a bit worn. The other thing I am considering is carbon friction paste.

 

[Yellow Fang]

Have you contacted Brompton themselves?

No, I have not done that.

 

[Yellow Fang]

Why not try it? After all, they may have experience of your problem and a solution to hand.

I was not aware they had a support site. I have emailed them for advice. Cheers.

 

[chris folder]

Hi the rubber sleeve inside bike where seat post slides into wears after time. Some dealers take it out and re new it they use heat to remove old sleeve.

 

[TheDoctor]

The sleeve is plastic. Nylon IIRC. Not rubber.
It's held in with a rubbery glue.

@mickle is a Brompton trained mechanic, hopefully he'll drop by soon...

 

[chris folder]

Hi the rubber/plastic sleeve inside bike wears and when it do the seat post can slip some brompton dealers remove the sleeve with heat to put a new sleeve in. I would check that area on your bike

 

[T4tomo]

Hi the rubber sleeve inside bike where seat post slides into wears after time. Some dealers take it out and re new it they use heat to remove old sleeve.

The sleeve is plastic. Nylon IIRC. Not rubber.
It's held in with a rubbery glue.

@mickle is a Brompton trained mechanic, hopefully he'll drop by soon...

Hi the rubber/plastic sleeve inside bike wears and when it do the seat post can slip some brompton dealers remove the sleeve with heat to put a new sleeve in. I would check that area on your bike

My (Ti) post slips down a little occasionally under heavy breaking, and occasionally slips round if I knock it with my thigh when out of the saddle, but I can thump it back straight on the move. i just tighten to clamp bolt occasionally if it's giving me a problem.

 

[StuartG]

My approach, probably with the aid of the dealer, is simply exchange seat posts with another Brommie. Does the problem move or stay?
That tells you whether it is the seatpost or the tube. Saves wasting time on trying to fix the wrong thing.

 

[Yellow Fang]

Brompton support recommended I take it into the bike shop and get the seatpost sleeve replaced, so that's what I did. I will soon find out if that fixed it.

 

[chris folder]

Hi good idea should be ok after new sleeve Fitted. if you keep tightening up clamp on post to stop slippage when rubber/plastic sleeve is worn the frame could develope a crack around seat post clamp area that can happen on old bikes where sleeve never replaced. A crack can appear