I am currently riding a Guru Ti road bike with a 27.2 Easton EC90 seatpost that keeps slowly slipping down into the frame. In an effort to help keep the post in one place I purchased a Salsa LipLock seat collar, but even at 10 nm of force the post will still slide scraping little bits of carbon off as it goes. Obviously, that is not good! Initially, I just tried the Salsa clamp and Finishline carbon assembly paste. After that failed to work I went ahead and sprayed a few layers of Krylon clear coat to help build up the post so it would fit more snugly. Now after a handful of rides the post is slipping again and the assembly paste seemed to have melted the clearcoat. So my question is: what other products could I use to help create friction so the post will stop slipping? Also, it will need to be safe for both carbon and ti. Thank you for your ideas in advance!
Have you been able to use a different post successfully?
I would have used clear epoxy on the post instead of clearcoat.
I have heard of Gurus with construction problems before.
I had a frame where the seattube was off-spec so the post kept slipping. A 0.05mm thick sheet of brass foil did the trick for me.
HugoDrax wrote:I know the frame is a 27.2 and the post is as well.
That's the nominal size. I was asking about the actual size of the parts. At this point I would measure both of them since it is obvious that one is out of spec.
I have heard of Gurus having similar issues such as slightly oversize press fit BBs.
if you imagine the clamp being larger than the frame, and the frame larger than the post, its easier to visualise that, when tightening, the parts have to slide against each other to shrink in circumference.
So after completely removing all of the remaining clear coat I went ahead and...
1. Put friction paste between the clamp and frame
2. Cut out and thinned a Fat Tire beer can for a shim
3. Insert the clean seat post with the shim and friction paste
I am now going to go for a ride to see how it works! Thanks everyone for the suggestions and hints!
I used a set of calipers on the frame and post to see what the true size is looking like:
Guru frame inner diameter: 27.305mm
Easton post outer diameter: 27.127mm
Then after a bit of math it looks like the area that I need to fill will be 7.6096 square mm and the brass foil I just picked up is 0.005 inches in thickness which in a simple loop should fill 5.4328 square mm. It looks like the carbon paste will add a decent amount of space filling (possibly too much) so I might have to see about sanding down this circular piece or just cover a portion of the post. Thank you everyone for your help! I will see what this new information can do for me!
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