rutan74

OK, I have a Trek Domane ALR. Previous bike was a Felt ZR3. Please no comments on the E-bike. Right now, at 66 I am loving it as it was time to get a little assist.

Problem is the saddle post keeps slipping a bit. I am finding it slips about 2mm on a 20-25 mile ride. I have a torque wrench and the collar clamp is torqued to 7nm which is the upper limit on the clamp. Now, I have not had my torque wrench calibrated so it could be off + or - a bit.

I have tried the Park slippage paste with little luck and this is why I am here as I do not know what to do at this point. I could if I can get the fame tube to open a bit more to put some electrical tape on the saddle post in an attempt to add a bit more diameter so the clamp holds better but I thought I would ask if anyone has another solution or just what they have done to fix this. Tightening the clamp more than the spec'd 7nm is dangerous as I know, so short of adding some thickness to the seat post, what else is there? Otherwise on longer rides I will have to re-adjust my saddle post at a given rest stop. Not idea since my position will then slowly degrade again and affect my overall position.

john

Rolla

The venerable beer can shim, while not ideal, has certainly worked for a lot of people over the years.

https://www.singletracks.com/mtb-gea...aluminum-cans/

freeranger

You could try valve grinding compound. It is a paste and is available in different grades-some finer to grittier and is available at most auto parts stores. One example: PerMatex Valve Grinding Compound 1.5oz (autozone.com)

easyupbug 

As freeranger suggested I have used valve grinding compound and it has worked well long term with no issues. If your wrench is a Harbor Freight type wrench a neighbor had a brand new one way off. I went with him after checking and the store manager said to wait until the new batch comes in as all he had in the store are way off.

Road Fan

One option not to ignore is to see if the next size up in seat post diameter is actually a better fit. "27.2 mm" may be the defacto standard, but usually there's no law saying standards have to be followed. If you have a good LBS, they may be able to find you something that fits, or perhaps even a commercial shim which does not come with the tricky tweaky problems of a beer can shim.

Not knowing where the motor and its bearings are, or how well the motor bearings are sealed, I would think twice about putting abrasive pastes into a tube carrying an electric motor, which could seize up if the abrasive paste lives in the ball bearings for long enough time.

I'm not saying this will be a problem, but I would tend to eliminate the possibility that it might be a problem, if the motor is located inside the frame. Even cheap Ebikes aren't inexpensive.

icemilkcoffee 

Get one of these rack mount clamps :

Clamp it onto your seatpost right where it meets the seat tube, so it can't slip down

Iride01 

Take a gook look at the clamp and any slot that may be cut in your seat tube. If the gap on either is closing and one side is touching the other somewhere, then it won't matter whether your torque wrench is accurate or not.

On an aluminum or steel bike and seat post, I certainly would try going to a higher torque. If you break the bolt, you are unlikely to have hurt anything other than the bolt and possibly the clamp which likely already needed replacing.

Or does your model bike have a clamp that is integral and can't be replaced? If so, I wouldn't resort to the overtightening thing until other fixes have been tried.

Crankycrank

Also try calling the shop you bought it from or TREK directly as they may offer a fix for no charge. Could be a common problem with your model.

Saudadeii

Make sure there's no grease, grit, corrosion, moisture, etc. in the seat tube or on the post. Check the "roundness" of the tube where the post clamps.

rutan74

WOW. It has taken me a while to respond here but that is a very interesting idea. These thin walled aluminum cans are probably ideal for a shim. I have used the beer can method to patch an exhaust a long time ago, but never thought about it in this case.

Thanks for the tip. I am trying the Park paste on the seat post and after my last 2 rides, it appears to be holding but I will surely keep this in mind.

Thanks, john

rutan74

Nice. Thanks for that tip. I will look for this and keep it on hand and give it a go if my current Park compound does not hold up.

thanks, john

rutan74

Right now, my post is fairly tight but I did think going up to bigger diameter post. For me, that is a last resort. Right now, testing the Park paste and after 2 rides it seems to be holding but keeping my fingers crossed.