Slipping Seat Post

[Newcastle Dave]

Any ideas on how to stop the seat post slipping on my Titanium Bossi Summit (carbon seat post). I have had the bike for a few months now, and its only in the last month I have had an issue with the seat post slipping down.

I have removed, cleaned and redone with carbon assembly past, tightened to 5.5 - 6 Nm, but it still slips down during a ride (I weigh 95 kg so apart from losing 25 kg I am out of ideas)

[tallywhacker]

same problem until I tried a gorilla grip seatpost clamp with 2 fixing points, one around the seatpost tube and the other around the seatpost

https://www.aliexpress.com/item/1900707378.html

[peter]

Apply some carbon paste on the seat post, then torque to spec.

My gravel bike has carbon seat post, the shop where I bought the bike did not tighten it properly. As the seat post sunk it created a big scratch. I complained about it, they replaced the seat post with an used one that has a different saddle adjustment mechanism. I wasn't happy but left it at that.

After awhile the seat post sunk again, ever so slightly. So I went to a different bike shop for help, the workshop gave me a packet of carbon paste, no charge and problem solved.

The first shop was in business for 22 years at the time, can't believe their mechanic doesn't know how to tighten a carbon seat post properly. I think he's the owner/manager, not some casual apprentice, very disappointing to say the least and never spent another cent there.

[trailgumby]

I had a similar issue with my new Cannondale SuperSix Evo. Solved by reading the instructions ... which said to cover the *entire inserted length* generously with carbon paste, and the interior of the seat tube as far as you can get your fingers in. I had just been covering the clamp area.

Once done like that it stopped slipping and my knees were happy.

I use this stuff. Much cheaper in the long run than mucking about with those little sachets at $4.50 a pop, that leak once opened.

[robbo mcs]

Any ideas on how to stop the seat post slipping on my Titanium Bossi Summit (carbon seat post). I have had the bike for a few months now, and its only in the last month I have had an issue with the seat post slipping down.

I have removed, cleaned and redone with carbon assembly past, tightened to 5.5 - 6 Nm, but it still slips down during a ride (I weigh 95 kg so apart from losing 25 kg I am out of ideas)

I have a bossi summit with carbon seat post, and was slipping from day 1. Tried repositioning and re tightening, carbon paste etc, helped but still slipped. I changed the tightening collar to a different one, and it hasn't slipped since. The collar that came with the bike was quite thin and stylish looking, the one I replaced it with was slightly thicker looking. Bike has been perfect otherwise

[RayG]

I had this problem. I couldn't even stop an aluminium seat post from slipping with the Bossi clamp. Ending up buying a two bolt post by Pro.

When I slide a clean post into the seat tube, it rattles around like the seat tube is slightly over size. Anyone else noticed that?

[RayG]

FWIW, my carbon post eventually cracked in two lines where the gap in the rear of the seat tube is. Bossi gave me a titanium seatpost as a replacement.

Saw James Bossi at an event last weekend. He said they'd found a shipment of their carbon posts were under sized.