Bicycle Mechanics - HELP! my seatpost is slipping! :(

I bought a new seatpost. Same size as the one I had but lighter(;)). 27.2

My former seatpost had a dull finish and kind of rough to touch. But my new one is super shiny!

My problem is. If I move my butt while on the saddle, the saddle seems to rotate. And eventually after some time, I notice my seat is getting lower. After about 30mins to the ride I stop and adjust the seatpost to its orig position.

Any tips?

BTW, the seatpost is "Dimension". Cheap, $25US, and lighter than my old seatpost.

Thanks

I had the same problem and tried first just to clean out the tube in the frame with a rag and that helped a lot, but then I got a little more slippage so then I gave a light rough up to the inside of the tube in the frame with a fine grain sandpaper. Not sure if this is the best way but I haven't had a problem since.

Good luck!
Damo

If your seatpost clamp is a collar that sits on top of the seat tube, try replacing it. It worked for me. ~ $8 at the LBS. I used one marketed for BMX on my mountain bike.

just put some sticky tape round the seat post- not very elegant but it works

just put some sticky tape round the seat post- not very elegant but it works ...and hope you NEVER have to take the post out of the tube again. "Overstuffing" a post/tube interface with something like tape just sounds like a recipe for a permanently stuck post. If it doesn't get the post stuck permanently, it will probably compress and work loose over time, causing the post to slip again.

Are you absolutely sure 27.2 is the right diameter? The old post might have been too narrow, but happened to work anyway because of its finish. If you can get your hands on one, try sliding a 27.4 post into it. Don't try too hard! If it doesn't go right in, then never mind, it's probably a 27.2, in which case the above-mentioned new collar idea might be best. Or just make sure you've tightened the allen bolt sufficiently. Again, the old post might have just been more tolerant of an under-tightened bolt.

...and hope you NEVER have to take the post out of the tube again. "Overstuffing" a post/tube interface with something like tape just sounds like a recipe for a permanently stuck post. If it doesn't get the post stuck permanently, it will probably compress and work loose over time, causing the post to slip again.

Are you absolutely sure 27.2 is the right diameter? The old post might have been too narrow, but happened to work anyway because of its finish. If you can get your hands on one, try sliding a 27.4 post into it. Don't try too hard! If it doesn't go right in, then never mind, it's probably a 27.2, in which case the above-mentioned new collar idea might be best. Or just make sure you've tightened the allen bolt sufficiently. Again, the old post might have just been more tolerant of an under-tightened bolt.

Its definitely 27.2, since the 27.4 won't fit, we tried at the LBS.
The seatpost that came with the frame was 27.2.

well, its the LBS(where I bought the frame and seatpost) problem now... :D

I bought a new seatpost. Same size as the one I had but lighter(;)). 27.2

My former seatpost had a dull finish and kind of rough to touch. But my new one is super shiny!

My problem is. If I move my butt while on the saddle, the saddle seems to rotate. And eventually after some time, I notice my seat is getting lower. After about 30mins to the ride I stop and adjust the seatpost to its orig position.

Any tips?

BTW, the seatpost is "Dimension". Cheap, $25US, and lighter than my old seatpost.

Thanks
I had the same problem on a Waterford I owned. 27.2 will fit if they clamp it down real tight. Look at the back of the seat tube lug. Is the space bigger at the bottom than the top or is the slit compressed so much that it touches? Have the LBS measure the ID in several directions. Sometimes the 27.4 ID can be measured by turning the calipers around in the seat tube. Good luck.

I forgot to ask, what kind of bike is it?

Tim

may need an Al beer can shim or a thinner one from the "Red Bull" can. No joke it works.

Don't rough up anything with sandpaper and avoid a shim unless using a shim is spec'ed by the frame manufacturer as a shim creates a stress riser which locally loads the post and seat tube. The least invasive method is to degrease both the post and seat tube I.D., spray the seat post with hair spray...the part that penetrates only, let is dry for about 30 seconds and insert the seat post to the desired height...what I and others do with great success.
HTH,
George

Don't rough up anything with sandpaper and avoid a shim unless using a shim is spec'ed by the frame manufacturer as a shim creates a stress riser which locally loads the post and seat tube. The least invasive method is to degrease both the post and seat tube I.D., spray the seat post with hair spray...the part that penetrates only, let is dry for about 30 seconds and insert the seat post to the desired height...what I and others do with great success.
HTH,
George
Yeah, use "hairspray" if you wanna to have a "sticky" problem :rolleyes:

IF- you are using the correct size post, take it out of the seat tube, clean both it and the inside of the seat tube and apply a thin coat of bike grease to the post. Insert the post and tighten the collar. That's it. That's what I've been doing for years. I know it sounds crazy to use slippery grease to stop something from slipping but all the shops I know of use this technique too.

sj