BB86 Bottom Bracket too long?

Question

I upgraded my 2016 Canyon Endurace with a C-Bear BB86 DUB ceramic bottom bracket to fit a Quarq PM. The BB didn't last a year, but I managed to get a replacement on warranty. The BB I received was exactly the same but "gen2". However, my problem is that it is far too long so it will not fit all the way into the BB shell.

I have attached an image with a standard SRAM BB86 DUB BB on the left, and my warranty replacement BB on the right. My Endurace BB shell has a lip, so the SRAM BB fits perfecty, but the C-Bear BB will hit the lip before it's inserted all the way, and therefore end up sticking out.

The SRAM BB is awful and creaks, so I've currently gone back to my ultegra cranks while I decide what's best to do (so no power meter).

The C-Bear BB has a scribed line around it which matches how long it needs to be to fit my bike, but surely I don't need to cut it to size at this point?

Why is this C-Bear BB so damn long? Do new BB86 frames not have a lip anymore?

Any advice appreciated, cheers.

Answer 1

I am not able to find a formal technical diagram of the BB86 shell. Thus, what follows is speculation. It does seem like the official specs from Shimano call for a lip/step. This page by Lightning Bikes does say so explicitly. The diagram there is a brief one, reproduced below:

Basically, I wonder if the official specs don't specify exactly how deep the step in the shell should be, maybe leaving the fine details to the discretion of the frame designer. The cups can be shorter than the step and still install correctly. If this is true, then perhaps Canyon made the step shallower than many other companies, not anticipating that someone would put such a deep set of cups in the frame. Or perhaps the usual practice for everyone has drifted over time (i.e. many frame manufacturers now realize that they need to make the steps deeper, maybe to support the cups better to prevent creaking, but they did not do this in 2016).

This is something you should definitely raise with C-Bear.

In contrast, see the diagram of an FSA BB386 shell below:

There's a step, but the stepped area (whose dimensions appear to be 14mm minimum) is a smaller diameter than the rest of the shell. So, again, there's not an exact specification about the length of the stepped area, but manufacturers exceeding the spec (as long as they adhere to the stated minimum) wouldn't cause a problem. Do note note #2 in the diagram, where it says that all details not explicitly specified are left to the frame designer's discretion.