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I need help finding a pressfit BB (BB386) for Shimano 24mm for my road bike. I have a Felt FR30 2017 bike, I checked the Felt website to find my bottom bracket and it said this: "40- BSA BB386". What does the "40" mean? Is that the diameter of the frame bottom bracket shell? I've checked most bottom brackets and they have a diameter of 46mm so I am confused.
You've got a BB386 shell and Shimano road cranks, which are all 24mm. There are a lot of individual replacement bottom bracket models that could do what you need here. The expensive ones are often this sort:
The cheaper ones are usually BB models that go in both BB386 and PF30 shells (which use the same 46mm bore but are different widths) and have dust seals that telescope to adapt. This would be used along with a plug-in style 30mm to 24mm crank adapter:
The setups that don't use an adapter are at least conceptually better because the adapter (aka reducer) wastes space that could be used for bigger, more durable ball bearings.
If what came with the bike is a 30mm bearing plus stepdown adapter type setup, the actual cheapest way to fix the BB will usually be put new standard BB30 type 6806 bearings into the existing cups and reuse everything else. (These are the most common type of BB30 replacement bearings and are available as bearing-only). If you got decent life out the bearings the first time around and things are mostly still in good shape, there's not a lot of reason not to do it this way IMO. (To do this you would typically use the same tools used to remove and install BB30 bearings).
It's not clear what your "40-" means but it's possibly part of a model number for whatever BB unit was in there stock. The reference to BSA in the same line could be part of a shorthand for someone trying to say it's a type of 30mm to 24mm conversion BB, since 24mm is originally more associated with traditional threaded shells. None of it matters since you know what the shell standard is now.
I’m not able to locate a set of original specs that say what you reported. BSA means an English threaded bottom bracket. BB386 should mean a press fit BB, with diameter 46mm, and width 86.5mm, I.e. same diameter as Pf30, but quite a bit wider. Those standards are incompatible. If you accurately reported the specs, then Felt is wrong. (Or it’s possible that the lower end versions have BSA BBs?)
It’s not clear what the prefix 40 means, either. It’s not in the nominal dimensions of the BSA spec, and it wouldn’t be necessary to specify any of the BSA nominal dimensions either (if the frame were BSA).
If you like, you can post a photo of your frame. If it could be either BSA or BB386, then it should be easily possible to distinguish the shell types visually.
