I am considering replacing the crank that came with my Cannondale Killer V900 mountain bike, which is a 22x32x42 (175mm), with a Sugino XD300, 26x36x46 (170mm). I had thought about changing the 42t chainring to a 44t, but I am now leaning toward replacing the whole crank with the Sugino. I am mostly interested in using the bike as a commuter/'spin like crazy' exercise bike, hence my going with a 26x36x46 (170mm) crank.
My questions are these:
1) My BB shell measures 70mm, and I wonder if these were Cannondale proprietary sizes and if this might portend difficulties in finding an appropriate BB, if I have to replace the stock BB. The bike was purchased new in 1994.
2)Can I use my present BB, which is not a sealed catridge type? or would I need to buy a new BB? The spindle interface type of the Sugino is Square Taper JIS. I do not know what this means.If I can use the stock BB, should I insist on it beign repacked?
3) The Sugino XD300 is made of steel, weighs 860g and sells for $45.The XD600 is made of alloy, weighs 690g and sells for $67. Is it really worthwhile to spend the extra $22 to get the alloy?
4) If I am going to have to replace the BB, what is a good brand and model to buy, that is reasonably-priced, stiff and ultra-dependable?
By the way, I have a Shimano LX Front Derailleur and a 7-Speed 12x28 cogs.