netorius77

Someone - please help me. I purchased a second hand 2003 Giant NRS Air with full Shimano XTR components, and Mavic Crossmax wheels. I have had nothing but grief with this surposedly pretty high end setup. I am reasonably mechanically minded, but this has me stumped. I have read through numerous posts on the subject with no definitive answer.

It started off with having to get the front middle chainring replaced as the original one was damaged/bent. That done, they changed the chain and rear cluster at the same time. I could now ride on the middle chain ring, but on a down hill, the chain somehow got caught against the tyre. I sent it back but apparently there was some problem with the Crossmax freewheel hub which they serviced and seems to be resolved although if you are peddling fast on a downhill in a high gear and stop abruptly, it does tend to catch - I can live with this.

Now my major, so far unresolvable, problem. When ever I am climbing a steep hill in a lowish gear, I seem to get some kind of slipping of the chain (or possibly free wheel hub). It doesn't move out of the selected gear, just "slips" what feels like a tooth or so every pedal rotation or so. I cannot work out exactly where it is slipping, but pretty sure it is at the back and not on the chain ring. It is ususally middle chain ring, and second or third gear at the back when this occurs, and under considerable load (climbing).

It really has me stumped. Being a full suspension bike I thought it may be flex in the frame/swingarm, but this doesn't seem to be an issue at all as all the bushings/ bearings are tight with no perceivable play.
My chain ring is an XTR P-46/34/24 with an HG53 chain and a 34/30/26/23/20/17/15/13/11 rear cluster. As stated the rear wheel is a Mavic Crossmax including the freewheel hub. General no load shifting is fine. I have tried to simulate the problem on a bike stand with no success. How do I access where the problem lies?

Any suggestions would be greatly appreciated.