My seatpost slips no matter how hard I try, After a few miles I have to stop and raise the seatpost at least 5-10 mm and it's pretty annoying. I've tried tightening the Turtleneck clamp as much as I can but to no avail It's seems like the clamp isn't strong enough. I've cleaned the shim and the seatpost but it doesn't do the trick... The seatpost and the shim are new by the way. I am trying to get to the point that it doesn't slip and you don't need to break a finger when tightening the clamp.
Any tips, suggestions, thoughts ?