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Bottom Bracket Help

dannbodgedannbodge Posts: 1,029
edited July 2017 in Workshop
I've got a 2017 Specialized Tarmac SL4 Sport with the Praxis Alba crankset.

I want to switch it to the Shimano Ultegra crankset so I can run a stages power meter and save a bit of weight.

However I do not know which BB my bike currently has fitted.
Can anyone help?


  • imposter2.0imposter2.0 Posts: 11,767
    Ten seconds on google tells me your bike has a threaded BB. Not sure you're going to save much, if any weight though.
  • No real world experience,
    but this suggests it's a proprietary Praxis BB which looks like the M30 family. The Spesh website says your BB is threaded, and Praxis seem to say it's not compatible with any other 30mm spindle apart from theirs. No idea if that's true, but you might need to replace the bearings/with an adapter to run Ultegra.
  • dannbodgedannbodge Posts: 1,029
    I'm fine with changing the BB and replacing with an adaptor. I figured I would need to do that anyway.
  • imposter2.0imposter2.0 Posts: 11,767
    You won't need an adaptor. If you have a threaded BB shell and you want to fit an Ultegra chainset, you just need a Shimano HT2 BB.
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