I love biking, but I'm really no mechanic. I currently have a Shimano M6100 groupset (Deore) with me. A friend is going to give me a good deal on a carbon MTB frame, but I'm worried about compatability, particularly the bottom bracket (BB-MT500-PA). The frame specs describes it as "PF 30 bottom bracket" and "46*73 mm" with the Greek fie or phi symbol in between. Would that work or fit?

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  • For reference, the phi symbol means “diameter”. It’s supposed to be a perfect circle with a line through it, but I presume that the phi symbol is less obscure. It should be ⌀
    – MaplePanda
    Jan 11, 2021 at 2:05

1 Answer 1


Bottom bracket standards are numerous and confusing. Have a look at https://wheelsmfg.com/bb-standards. That's the best online resource I have found so far that explains them.

PF30 bottom brackets are designed for a 30mm crank axle. Shimano cranks have a 24mm axle. What you need is a bottom bracket that adapts between the PF30 specification frame and the Shimano crank. An example is https://wheelsmfg.com/pressfit-30-to-outboard-bottom-bracket-for-24mm-cranks-shimano-black.html. Other manufacturers make similar products.

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