Originally Posted by
norwood
I think the OP is refering to the seatpost/saddle rail junction.
Take it all apart and examine every piece. Make sure there are no burrs or any foreign material that could keep the clamp from tightening properly. It's a simple apparatus, there can't be too much wrong with it, unless it's cracked or something. Why would you ride it without it being tightened correctly?
Oh that makes sense.
Uh, OP. Take apart the entire clamp clean the grease out of the splined interface, regrease the bolt itself and reassemble. While the seat is out - visually inspect the condition of the rails to see if they've been worn away.