I have a question for all you mechanical gurus: I recently bought a trek 7100 hybrid. It skips between the biggest and second biggest cogs on the rear cassette, I have had it into the local lbs 3 times over teh last 6 weeks and it never quits for long. Could this be due to bad or inferior shifters, derailer. chain, or cassette, or all of the above? Like I said this bike is new and should be shifting smoothly. all other gears shift quite well with the exception of once in a while somewhere in the middle of the cassette it will skip. By skip I mean it shifts down to the smaller cog and once you put a lot of pressure on the pedals it will skip back to the larger cog. this is sometimes iratating others have almost caused me to spill.I like the bike a lot other than this ((well my wide but is not happy with the saddle yet)) I am willing to go to a different derailer as this has the sram esp 3.0. i guess the next question would be what would work with this cassette? or would it have to be changed as well?