I'm probably going to end up bugging P20 about this tomorrow, but I thought I'd try to get an answer here first cos it's his birthday and I think he's getting fed up of my stupid bike-related questions...
I have an ancient (?1992) cheapo rigid steel MTB that I use as a commuter cos I can leave it outside the hospital without it getting nicked. However, the drivetrain has seen better days and there are now very few gears that actually work. So I need to replace lots of things.
It's currently got a triple chainset (22,32,42), 7 speed cassette and square taper BB.
I have seen this crankset on CRC which fits my budget for this bike perfectly (and gives me a more usable range of gears for my commute). However, I have no idea which bottom bracket size I am looking for. The shell on the frame is 68mm wide, but I don't know which spindle length will fit my bike/those cranks.
I'm looking at this Shimano BB. Can anyone help me size it correctly, or should I just buy all the sizes and send most of them back?