Seat and post keep lowering

[marymary]

Hi - this seems a silly one, but when I cycle, I start of with a high saddle and by the end of the ride (eg average commute of 10 miles) the seat post has gradually lowered. I had problems with my knee(excruciating illiotibial pain) which is resolved when the saddle is raised, and I was under the illusion for a while that my legs were stretching to extraordinary lengths as I seemed to be having to raise the saddle every ride. Anyway I marked the seat post at the desired height and discovered that it gradually sinks back down made evident by the return of the sharp knee pain. The clamp seems rock solid on the seat post, I have renewed the screw twice just in case,but the problem persists - any ideas on how to resolve this? it is a brand new city bike.

Mary

[thirdcrank]

The clamp (of whatever type) which holds the seatpost in the frame isn't tight enough. If you have really tightened it up, it's possible that it hasn't enough adjustment to do the job. There are various solutions, depending on how the frame is made. As the bike is new, I'd suggest back to the retailer pronto, and don't be fobbed off. Either, the bike is faulty and needs fixing, which is the shop's responsibility, or it's something glaringly obvious we have both missed and it should be corrected with a cheerful smile as a token of goodwill. (If you bought it mail order, see what the retailer has to say - it's still their responsibility if the bike isn't right, but it's harder to sort out at a distance.)

PS I suppose it's possible that the seatpin / aka seatpost is not the right size, although I'd expect that to mean it would be really loose in the frame.

[531colin]

As its new, the post should be the right size!
Sometimes the bolt gets to the end of its thread before the post is held tight...sorted out by an appropriate washer or two.
Sometimes there is debris in the slot in the tube so it won't squeeze together enough.
Shouldn't need shimming with a bit of Coke can...

[Steve Kish]

If you have a collar as opposed to a brazed-on fittings, this will do it:-

http://www.carboncycles.cc/?s=0&t=0&c=73&p=851&

I use these on my two alloy frames with alloy pillars and even with light tightening, they are bullet-proof!

[Malaconotus]

Seatposts can slip, and there are several solutions. To solve my continuing problems with a new 400mm seatpost I used emery paper to scuff up the top two inches of frame tube and my lager can shim (Stella cans are the tallest available) and also fitted a new seat clamp (a bit of bling)

But as TC and Colin say if you bought from a good shop you shouldn't have to go to any of these lengths or expenses. It's a new bike, so it's the seller's job to fix it. Take it back and get them to investigate and resolve. Did they include a free first service or check of the bike after you'd ridden it a few weeks?

[Malaconotus]

If you have a collar as opposed to a brazed-on fittings, this will do it:-

http://www.carboncycles.cc/?s=0&t=0&c=73&p=851&

I use these on my two alloy frames with alloy pillars and even with light tightening, they are bullet-proof!

That's a neat idea. Only works if you have standard tube and seatpost size combinations, though. Wouldn't work with my 27.0 post, for example. And no QR, either.

[thirdcrank]

... But as TC and Colin say if you bought from a good shop you shouldn't have to go to any of these lengths or expenses. It's a new bike, so it's the seller's job to fix it. ...

Friendly discussion should sort this out, but If it turns out you bought it from a bad shop, including one where the answer is that you'll have to wait while they see what the manufacturers have to say, then Consumer Direct may be the next port of call. http://www.direct.gov.uk/en/Dl1/Directo ... /DG_195948

[hufty]

I had this problem on my mountain bike (Thomson seatpost, steel frame) , and a suggestion which has worked is to degrease both the post and the inside of the frame, then dust the post with tailors chalk or climbers chalk. See http://forums.mtbr.com/showthread.php?t=209789. Post and frame haven't fused together so far.

[marymary]

thanks for all the advice. the shop offered any repair to be paid for by them at a good local bike shop, so fair dues. In any event my husband put on a better screw thing (bolt?) and it has stopped.