Hi I am a bit baffled, all of the usual fixes don't seem to fix this slipping seatpost of mine.
Campy NR seatpost is the correct size for the frame('51 Rotrax, 531 tubes). Seatpost is a very good fit in the seat-tube. Seat-tube has been flex-honed(last week). Seat-post shaft is in excellent condition. Seat-lug slot is not pinching closed when tightened. Seat binder bolt is not bottoming on the threads at all. Everything is cleaned and greased prior to assembly. Sufficient torque is applied to the bolt.
Despite all this, it slips about 0.5" in 40 miles. Is there something I am missing here?
Rosin on the tubes will give you a bit of "BITE". It has worked for me.