Bottom bracket not sitting flush?

Today while doing a workout on the trainer I realized that there was a small gap on my bottom bracket. As you can see below it doesnt seem to be sitting flush to the frame there’s like 1-2mm gap. Is that something I should be worried about?

Worried…no, but it does mean the frame could do with facing.

Thanks for the reply but I’m not sure I undertand what you mean by “it does mean the frame could do with facing”

At the risk of being lambasted for the mention of the name… Hambini on youtube has some probably highly relevant info here.

TLDR = carbon frame tolerances by some prominent manufacturers are such that perfectly machined BBs won’t fit perfectly. Probably nothing to worry about safety wise. Might cause premature BB bearing wear. Probably possible to fix/adjust if desired.


Before looking at frame tolerances etc…have you checked it is actually tight? And if it is tight, do you know that it hasn’t been cross-threaded?


It’s a process where you remove parts of the frame (using the correct tool) material so the surface is perfectly flat. It’s quite common but others here have made some good suggestions like checking the install of the BB.


I don’t think that’s a gap. To me, it looks like the metalic part is just missing some of the black coating (paint / adhesive???).


On closer look… you may be right.

I don’t see a gap…

Yeah, not sure it’s supposed to be like that, rotated and pointed out for everyone.

Can you share what frame this is on and what bottom bracket is installed?

Bit of a hack job, but it imagine it should look more like this if properly installed.

^ thats exactly what I meant. Frame is the Tarmac SL6, FACT 10r carbon and bottom bracket is the Praxis, BB30 for Shimano that came stock with the bike (Men's Tarmac Disc Pro |

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Ok, you should be good to go, that’s just the way the Praxis BB is designed. :+1:


Ah! Great thanks