Crankset and BB Madness

Forums Mountain Bike Forum Crankset and BB Madness

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    • #500280

      I’m trying to convert my bike from a 3×9 to 1x setup but running into issues with the crankset. Bike currently has a Shimano Alivio (FC-M4000) crankset with the 30t chainring being completely worn down. I looked around to see if there was an easy way to get a single chainring crankset on the bike but apparently the Shimano Octalink bottom bracket supports exactly one MTB crankset which is the same one I have on there now.

      What’s the most inexpensive option to get a single chainring crankset on this bike? Do I need to replace the bottom bracket? If so can anyone recommend a good BB/crankset that would work?



    • #500333

      I swapped out my 2×9 with a Eagle GX 1×12, needed a DUB BB.

    • #500401

      I am not sure if your chainrings are removable on that crank. If so it is simple, replace the chainring and go with a 1×10 or 1×11, leave the old crank on but remove the rings you don’t use. You could get away with keeping your BB and crank and just replace the cassette, chain and rear derailleur and shifter. The minimum size of a 104mm bolt circle chainring is 30t if it is an even bolt pattern.  If it is a 3×9 bike I assume there are other aspects of the bike (geometry, suspension) that are not the latest and greatest. Don’t dump too much money into the bike if that is the case. 1×10 stuff is inexpensive.  Keep the upgrades inexpensive and save your pennies for a bike that has what you want.

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