Bicycle Mechanics - Crankset/derailluer compatabilty

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hoovec

03-22-09, 10:50 AM

I'm rehabing a 15+ y.o. beater mtb used for road use which has a Shimano 7 spd drivetrain, rear derailluer labeled Mountain Lx, front just labeled Shimano. The middle ring needs replacement. It would be cheaper to replace the entire crankset with a Shimano CO51 set listed as "8sp", but will it work? Thanks All!

laura*

03-22-09, 11:06 AM

rear derailluer labeled Mountain Lx

replace the entire crankset with a Shimano CO51 set listed as "8sp", but will it work?

It probably won't work. The C051 crankset is speced to use a 122.5 width bottom bracket spindle. I don't know what your existing crankset would use, but it is probalby something narrow like 107 or 110. Putting the C051 on your old spindle will position the gears too close to your frame.

Of course, you could replace the bottom bracket too - and it probably needs to be replaced anyway by now. However, this changes the cost equation.