My new Roadrat, single Alfine crankset, rear 105 short mech with 9 speed 12-25 105 cassette, new XTR chain and cable… all setup by me (whom I thought was a good mechanic) Why am I having trouble at the "big" end of the cassette ?? Got perfect dialled shifting from the 12 tooth up to the last 2/3 sprockets, then it all goes t**ts up. Bottom of a hill today, go to move off and there's all sorts of skipping, trying to change to the next cog etc… Really is doing my head in now. Anyone come up with something to look at ?

if it shifts ok at the top but not the bottom (or vice versa)i'd look at a bent hanger.

straight as a die it is, part of the removable "dogs body drop-out"