Originally Posted by
gauvins
Will eventually try with a different clamp. In the meantime: the seatpost isn't positively locked in place, despite the bolt being properly tightened. The frame is a Surly Troll. The seatpost is a Nitto, 27.2mm. The clamp is stock.
There is some grit on the clamp, but it doesn't seem to interfere. As we are currently traveling, I don't have solvent on hand, so we adjust frequently.
Any idea what could be the cause??
Another thing to do (along with cleaning and greasing everything) is to ensure the gap in the clamp is aligned with the gap in the seat tube:
If that doesn't fix it you can make a shim from an aluminum can or get the Surly heavy duty clamp.