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« on: June 20, 2010, 09:26:46 pm »
You will have chain drops and other shifting problems, but they'll be with your front derailer, not your rear derailer. A gap of even 12 teeth like yours came stock can be too many, and bringing that to 14 is almost certainly going to kill it. The chain will end up getting stuck between the chain rings, and even if your mechanic can shim that issue away, the shifts will still be slower and you'll have to slow your pedaling to get it to catch. And you would then almost HAVE to use friction shifters of some sort; indexed shifters like STIs cant handle a shim kit.
As to your options that won't be more trouble than its worth, you can get a 11-36 cassette like the SRAM Apex or the 2011 XT or SLX, which will drop you to 22.5 gear inches, but to drop below 20, you'll need to replace all of your chain rings. Your current top gear ratio is 127, which is unnecessary. Anything above 100 and your really reaching a point where you should only use them on a hill so steep that you could gain speed faster by tucking than you ever could from pedaling. So you can afford to replace your big chain ring. With that cassette, you could run a 46-36-26 or a 44-34-24 and never miss the loss on the high end. I see no reason that you would have to replace anything but the chain rings ($15-35 a piece, depending on quality), but your mechanic will understand what your options are better than I can.