I have an oldish bike around 8 years old.

My bottom bracket has started to make a clunking/clicking sound.

It currently has a SM-BB51 fitted. I'm unable to find a exact replacement in stock. I'm taking it is now end of life.

What other bottom bracket could I replace the SM-BB51 with?

Thank you for your help.

  • Before you blame the bottom bracket, take off the pedals and grease the axle threads... It has been more than once that I though the bb has gone bad and it turned to be just pedals... Jun 16, 2021 at 13:23

1 Answer 1


Hello and welcome to bicycles.stackexchange.com

You will struggle to find components in stock anywhere right now given the global component shortage + covid.

As to your question, compatible parts are...

From Shimano:

  • SM-BB52 - Deore level component. Direct successor of your SM-BB51

  • SM-BB70 - SLX level component

  • BB-MT800 - XT level compoment. You will need a different tool or an adapter. I've recently replaced my SM-BB52 with BB-MT800. See this thread: SM-BB52 vs BB-MT800

  • SM-BB80 - Saint level component

  • SM-BB-93 - XTR level component. Nuff said

If you choose to go with other manufacturers you can grab anything that conforms to all of the following three standards:

  • 24mm spindle diameter
  • BSA threaded
  • 68/73mm width to match your frame

Good luck!

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