Juan Foote

Bought the wife a used Jamis at the local. She loves it, and we are riding frequently. Each time we ride she is having issue with the seatpost sliding down into the tube. It is the original seatpost to the bike, as well as clamp. It's one of the "lever" clamps, and I have it tightened to a point I can barely open or close it by hand, and it feels as if the lever will break if any tighter.

I took it back to the shop we bought it from a few weeks ago. Shame on me, it was Friday afternoon and moments before close. I asked the fellow behind the counter if he would apply some of the "paste" to the post so it could get grip. I could see him eyeing the bike with a mind towards thinking we didn't buy it there, it's not one of their brands. Without really having time to go into it, I just wanted him to put some paste on the post and tighten it down...where he goes on to argue with me that it is designed for carbon, and won't work...that they apply white lithium grease (which explains the sliding) to keep them from seizing. Long story short we are pretty much pushed out the door without a resolution and continued to stop every few miles to raise the post again.

I KNOW there is some manner of paste we used at the shop I worked to combat this. IDK if it were specific to carbon, metals, w/e, hell it may have even been tooth paste.
Can someone please tell me if they are aware of what CAN be used on a metal to metal seat post to stop it sliding without having to buy a new part of any sort? Or just what it's called?

ThermionicScott 

The seatpost should be a snug fit in the seat tube -- maybe it was *originally* shipped with the wrong one?

Have you tried lubing the QR? I've found that to reduce the effort. On my MTB, I switched from the QR to a bolt-and-nut setup, not to reduce slipping but because I wanted my saddle to be a little harder to steal.

Juan Foote

Well, I know when I look up the bike, and 09 Jamis, the picture and parts list is identical to this bike aside from the tires. Perhaps with was a problem common to the whole line. I have not seen that reflected in any post about the bike when searching for details.

As I said, I know there is something that can be used. It was white, pasty, and had what felt like sand or pumice in it.

Z953

I have very limited experiece from my three bikes (a complete upgrade and two build-ups done that I did myself) and I'm only familiar with a paste that is used for carbon fiber parts only (I use it for my seat post and bars). In all of the videos that I've watched and web pages that I've read, the only thing applied to non-CF parts is grease so that they don't freeze up (as Thermionic mentioned).

veloz

Replace the QR seatpost clamp with a bolt version. The seat tube should be lightly greased so it doesn't freeze in place. You shouldn't need any friction paste.

fietsbob

The factory that Made the Jamis stuff, buys seatposts chosen for price according to the model level.

They Dont Make them.. any hints as to which? Tried one 0.2mm larger?



Im @ 220# I cured slipping seat posts With a second Band clamp directly around the seat post, sitting above the Frame seat post clamp.

One is 27.2; the Brompton 31.9, got a 2nd QR band , since the post going down is part of the Fold.




'/,

ramzilla

You could try the aluminum beer can fix. Make a shim out of a beer can: (wear gloves) Cut a 1" x 3" strip out of an aluminum beer can with scissors. Mark the seat post at exact height you want it to stay. Open the seat post bolt. Wrap the aluminum strip around the post right next to seat post bolt. Tighten bolt. Test ride.

fietsbob

Precise Fit.

bhchdh 

Park Tool SAC-2 SuperGrip Assembly Compound
https://www.nashbar.com/bikes/Product...18_-1___204666
https://surlybikes.com/parts/small_parts/constrictor

TimothyH

Using assembly paste with grit isn't a substitute for a properly fitted seatpost and a seatpost clamp which is tightened properly. If the clamp is so tight that you can barely loosen it then something else is wrong.

Again, if the clamp is that tight then it isn't the grease which is making it slip. It would probably slip without grease. Something else is wrong.

Someone needs to check the fit of the post to the seat tube and the operation and fit of the clamp. Grease and paste on the seatpost are secondary issues.

Juan Foote

"or aluminum"

Thank you, I knew I wasn't imagining things.

Juan Foote

I will check again to make sure the clamp isn't splitting somewhere. It appears to have plenty of room between "tab closure", so it hasn't squeezed itself past the point of mechanically holding, that I can see.

FBinNY 

Two points.

1- to answer the specific question, the product you're asking about is often called "carbon assembly paste" and is OK to use on an aluminum post. There are two kinds, on uses grit one uses rubbery particles and doesn't scratch. You can also use lapping compound which you can beg from your local auto mechanic.

2- MORE IMPORTANT

Greased aluminum posts shouldn't slip. The fact yours does implies something else is going on. You can diagnose the specific issue with a quick eyeball check of two possibilities.

1- the cut slot in the frame tube is typically 1/8" or 3mm or so. If the post fits correctly the top shouldn't pinch closed much and the gap should be only a bit smaller than at the bottom. If the gap it the top is close to 1/16" when closed, odds are the post is undersized.

2- clamp bands often fail, not always by cracking. Look at the back of the ears and see if they touch (or even come close) you won't be able to clamp the post any tighter. If so, the only solution is a new clamp. Look for one where the ears transition to the band without an angle or notch (like this -- not this).

Lastly, if the post and band check out, you might solve the problem without buying anything. Remove the post and wipe it dry. Then wipe out all the grease to a depth of one inch or so in the frame. All the clamping happens in this top inch, so if you have it dry there you can still have grease below. Just be sure that as you insert the post you don't push it in too far and pull it back up, since that will smear the grease where you just wiped it out.