Join Date: Oct 2004
Location: DC / Maryland suburbs
Bikes: Homebuilt tourer/commuter, modified-beyond-recognition 1990 Trek 1100, reasonably stock 2002-ish Gary Fisher Hoo Koo E Koo
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Well, you *do* need to get the same type of bottom bracket spindle if you plan to keep your current crank.
There is absolutely nothing wrong with square taper BBs/cranks, they are widespread and reliable. It's just that the newer splined designs are slightly stiffer and lighter, and thus becoming more popular. There are essentially 3 such splined designs: ISIS (standardized, many manufacturers make ISIS cranks + BBs), Shimano Octalink version 1, and Shimano Octalink version 2.
I don't think 116 mm is a common spindle length unfortunately. I have replaced many bottom brackets with spindles that differed slightly in length, and I can assure that it's not a problem to tweak the chainline by 1 or 2 mm. There are basically only two major problems that you could run into: if the spindle is way too short, the inner chainring could whack into the chainstay, and if the spindle is way too long, the front derailer might not be able to reach all the way out to the outermost chainring. A 1 or 2 mm change in chainline is pretty darn unlikely to cause either problem.