[b rock]

My Reverb Stealth keeps slipping in my carbon frame. Any opinions on which brand of carbon assembly paste will best fix this, without scratching things up any more than is necessary?

I started with some red assembly paste that came with the bike (FSA?) and the seatpost tended to slip down occasionally. Then I bought some Finish Line Fiber Grip, and now it sometimes rotates when I nudge it with my knees accidentally, while climbing or descending.

I've read that the Park stuff has the biggest grit particles, but often scratches things up, so I am considering trying Muc Off Carbon Gripper, or maybe FSA. From what I read, Tacx seems less abrasive, so maybe won't get the job done, if the Finish Line stuff isn't working?

 

[Lone Rager]

Something seems wrong beyond choice of grip paste. How well does the post fit the seat tube and what torque are you using on the clamp? Is the post is rotating in the seat tube or is the saddle clamp rotating on the top of the stanchion, which is an issue that's been known to happen with Reverbs.

 

[b rock]

Something seems wrong beyond choice of grip paste. How well does the post fit the seat tube and what torque are you using on the clamp? Is the post is rotating in the seat tube or is the saddle clamp rotating on the top of the stanchion, which is an issue that's been known to happen with Reverbs.

The Reverb Stealth came stock on a Canyon Spectral 2018. Apparently, one of the Canyon mechanics remarked that the tolerance wasn't great, but I wouldn't say it is loose by feel.

I've stuck to the max torque printed on the frame for that screw, 4 Nm.

It's possible it's the saddle clamp! This started happening after I did my own 50 hour service on the dropper for the first time. I tried to do everything by the book (manual + rock shox video). So, if this is happening, the post that goes into the frame wouldn't be rotating at all, is that right? So, I would see the rock shox logo on the back of the post that inserts into the frame stay in the same spot as when I inserted it, correct?

 

[Forest Rider]

If you notice the seat twisting, confirm the seat post is not actually twisting, as mentioned by LoneRager.

My Race Face dropper allows the seat to rotate on the stanchion. Not intentional, more like a defect. I rotate mine sometimes while doing wheelies.

 

[Cleaner]

Motorex carbon paste is non abrasive.

 

[Lone Rager]

What kind of clamp does that Spectral have? From pix it doesn't look like a normal post clamp...maybe a wedge or something? Bikes here with normal clamps are between 7 and 9 Nm.

AFAIK, all carbon friction paste uses plastic grit so shouldn't be abrasive. Of the various brands I've used I've never been aware of a performance difference.

 

[Cleaner]

There are many posts (here and elsewhere) of people seeking a carbon assembly compound that does not scratch the components when used between parts. The particulates used in many products will abrade the resin at the surface of a carbon part because they are a higher hardness material which is the method by which the product increases the coefficient of friction at the assembly interface.

Motorex Carbon Grease.

Product Description
Motorex Carbon Grease is unique for a number of reasons. Most notable is that it lacks the suspended particulates you'll find in typical carbon assembly paste. Where the others use these microspheres to increase the traction between the slick finishes of carbon parts, the Motorex formula relies on a special ability to increase friction under high pressure. The difference is chemical rather than physical, yet the result is the same -- you'll increase the grip between parts and lessen the torque needed to attain the proper performance. Since it lacks the abrasive particulates, Motorex Bike Carbon Grease will not damage the glossy finish of your carbon parts. It is effective and safe for carbon/carbon and carbon/metal interfaces. Use it for handlebars, stems, and seatposts. Bike Carbon Grease comes in a 100g container. Application is easy with the brush on the underside of the lid.

 

[b rock]

What kind of clamp does that Spectral have? From pix it doesn't look like a normal post clamp...maybe a wedge or something? Bikes here with normal clamps are between 7 and 9 Nm.

AFAIK, all carbon friction paste uses plastic grit so shouldn't be abrasive. Of the various brands I've used I've never been aware of a performance difference.

It's an integrated clamp, with a surface inside the seat tube that adds pressure as you tighten the bolt. I can take a picture later. I will contact Canyon, and ask if they approve of higher torques in the case of slipping. For their road bike integrated seat post clamps, they recommend up to 7 Nm if slipping is encountered with the printed 5 Nm on the seat tube.

I'm not too worried about assembly compound abrasions, I just read that the Park Tool assembly compound was exceptionally abrasive, and scratched alloys beyond what some people were comfortable with. However, if the scratches are just cosmetic, and the Park formula works the best, I would consider it.

I'll clean the post and tube and reapply and ride this weekend, and keep an eye on what exactly is rotating.

 

[keen]

If you already tried different pastes you have other problems. If it were my bike i'd put the torque wrench aside and give it a crank w/ an Allen wrench. I used Park paste on a carbon post clamp and it really chewed @ the surfaces as it still had movement.