Sliding seat post
 

I brought a new touring bike last December. Because of the bad weather and the fact that I have other bikes I did not ride it until recently. Well, I have a major problem with sliding seat. It is really uncomfortable and it is embrassing because I have a little weight to my hips. I took the bike back to REI (they are nice people and the service is great.) Anyway, I explained to the service person my problem and told him that I am not happy. Has anyone else had a problem with sliding seat and what have they done about it.? Unfortunately, this is not the first time i had a proble with a sliding seat. My regular LBS corrected the problem and he was very apolibetic about it. Still,t hurts to have this problem.

Easy fix and you may have it already.

Get a seat post mounted reflector or blinky safety light. Set your seat to the height that is right for you and then put the clamp for the reflector on the seat post and slide it down to the union of the frame post and tighten the crap out of it. I bet this will completely solve your problem.

http://i425.photobucket.com/albums/p...s/IMG_0935.jpg

http://i425.photobucket.com/albums/p...s/IMG_0937.jpg

Good Luck

Jay

I had the same problem with my quick release seatpost clamp. If the thumbwheel on the opposite side of the lever has a hex socket, use an allen wrench to tighten it down. You won't be able to open the quick release lever, but the post will stay up better. If you have to adjust it, just use the allen wrench. The other added benefit, is that you can lock up your bike without someone stealing the seat (unless they have an allen wrench!).

http://i245.photobucket.com/albums/g...2008/Clamp.jpg

I would think some diameter is out of spec here. Or perhaps try another seat post clamp?
AFAIK, this should not happen with correct parts.

Depending on the bike it could be an easy fix.

I had this issue with my Giant Sedona, and tried a variety of fixes before I finally found the fix, and when I found it, I did a slap of the palm to my forehead...

I tried everything, including eliminating a QR collar and going to a bolt... I assumed the problem was my 350 pounds, and I may have done better at a lower weight, but the issue was corrected without having to lose a lot of weight (although the weight loss is still an objective).

For some reason, certain bikes (even from the factory) come with a seat post shim... and if the slot in the shim doesn't align with the slot in the seat tube it is virtually impossible to tighten the clamp enough to keep the seatpost from sliding into the seat tube during a ride. You can slow it down, but you can't stop it.

Once this was pointed out to me, I aligned the shim, and my problem went away.

If you have a shim... Try it, you'll like it.

+1. They should make sure it is tightened correctly. When tight enuf, the quick lever should almost be "impossible" to tighten by hand.

The only places QR seat posts are a good idea is off-road bikes where it's sometimes a good idea to lower the seat. For bikes that are used on the road and could potentially be locked up and left somewhere, all they do is make it easier for someone to steal the saddle, by opening the QR and sliding out the post and walking away. You come back to find your missing saddle and post. A bolt on seat post clamp means they need or need to find the proper tool, to open the bolt and remove the post.

Been there, done that, tried everything then got a Surly Constrictor for the everyday bike, and a Salsa Lip Lock for the bad weather beater. Both are excellent seatpost clamps and will solve whatever issue you may have.

I would take Lutz's suggestion and double check the diameters fo the seat post and seat collar against the manufacturers specs. I know Surly lists the name and diameter of the seatpost and seatpost collar. I am not sure if REI has the device (don't know the technical name) that measures the diameters, but I would think most LBS would.

Also when you take out the seatpost see if it feels greasy. I'm not sure how much that might affect it slipping but it happened once when I sprayed some Frame saver in my bike (though I am not sure if I re-tightened the collar enough).

1) my original seat post was a sloppy fit. I cut down a Guinness can and wrapped around the post as a shim, which helped.

2) I upgraded the seat post to a two bolt model (which I love, where has it been all my life)...and this upgraded post had a MUCH closer fit, a much better tolerance. No need for the shim now.

another tidbit...

tube and post tollerances can be as much as 0.1mm... so you could have a 27.2 tube, and a 27.2 post... if the post is on the small side @ 27.1mm and the tube on the big side 27.3 you're going to get some fit issues...

good luck man
mark

Urban I had the same issue with my novara from REI. I talked to the tech thinking it was my weight and he said nope it should never do that. He replaced the seat clamp and I have not had another days problem. He did mention that the clamps they had been using had done that a few times and he got them to order better clamps. so you may want to talk to the REI tech again.