Facing the bottom bracket

[Darrenjs92ni]

Does anyone here face their bottom brackets? I rubbed the face of mine with a oil stone would that give the same affect? How important is it to have the bottom bracket as close to 68mm as possible, I watch one video on the net that said the point of facing it is to get it closer to 68mm. But every other thing I have read says it’s to get the faces flat and Parallel. Which makes more sense to me as the adjustment compensates for length and I don’t see the point in chasing the threads as this would make the threads a lose fit (not at I would ever be able to afford the tool).

[DaveM]

The 68mm measurement is not that critical. The point of facing the BB shell is to make the two faces parallel and perfectly perpendicular to the threads. This is necessary to have the bearings aligned properly as various bearing configurations rely on different parts of the BB shell to clamp down to.

Facing is not that important for a cartridge BB because the bearings are held in alignment in their casing. But for three piece BBs or external bearing BBs, facing can have a big impact on bearing life and performance.

Chasing threads (done properly with a tool in good shape) won't make the threads any looser. But it's usually only really needed if there was some damage, corrosion to the threads.