I’m needing a new bb for my 2019 tcr. It’s a pressfit with a shell width of 86mm

Looks like shimano have 3 that’ll fit, sm bb71, bb72 and bb92. But before I press the buy button can i just check they will indeed fit and that the 71/72/92 don’t relate to some measurement I’m overlooking. (Assumed they just related to model – ie 92 is duarace, 72 is ultegra etc)

I know you get 71 mm bb shells, but they aren’t press fit as far as I am aware …but it is causing me a bit of confusion

The 71/72/92 denote position in hierarchy as you say, so are interchangeable. There’s also a 105/Tiagra level one.

Basically any of these will work.

BBRS500PB
BB7141B
BB7241B
BB9241B

Just been researching this myself and as above, you want the SM-BBXX-41B version for road BB shells.

Out of interest, what are you using to install it? Grease, retaining compound or going in dry as per Shimano docs? I’ve opted for Loctite 641 after too many hours spent Googling press fit installation.

Out of interest, what are you using to install it? Grease, retaining compound or going in dry as per Shimano docs? I’ve opted for Loctite 641 after too many hours spent Googling press fit installation.

Absolutely terrible idea for a press-fit BB using loctite. All you need is a tiny bit of grease to ease the cups in and thats it.

@tpbiker any Shimano PF for 24mm HTII will fit, they just get posher.

Cheers guys

Wad planning on a little grease, no loctite

Absolutely terrible idea for a press-fit BB using loctite. All you need is a tiny bit of grease to ease the cups in and thats it.

641 isn’t a thread lock, it’s a low strength retaining compound meant for cylindrical metal to plastic interfaces that may require future disassembly. It’s not to glue it in, but rather to fill any micro imperfections in the BB shell which can cause creaking. Plenty of info online about people successfully using it for PF BBs. It’s also lower strength than Park Tools RC-1 (basically Loctite 680) which is meant for the same purpose.

@tpbiker any Shimano PF for 24mm HTII will fit, they just get posher

They’ll all fit, but the plastic seal/spacer tube is a different length for different models. As mentioned above, B suffix denotes road 86.5mm whereas A is 89.5/92mm MTB and C is for wider 104.5/107mm BBs on DH bikes and SuperBoost bikes.

You’d be best getting the right one.