Which Bottom Bracket For Which Bottom Bracket?

“I just need a bottom bracket?"

“Oh yeah, which one?”

“Standard”

-insert face palm here

Bottom Brackets are the most un-standardised standard that there could possibly be in the bike industry. Knowing two key things can help make it easier, or at least point you in the right direction.

Question 1: Is the frame press fit or threaded?

Easy right? But also not. 

Press-fit bottom brackets are, well, pressed into the frame using a bearing press or whatever other high-strength method you want. These bottom brackets are generally single-use only. Once you put it in, good luck getting it out whole again, and realistically, you don’t want to reuse a bottom bracket you just whacked the bearings off with a hammer to remove it. 

Threaded bottom brackets thread into the frame. But there are two types of threads. English (aka BC, BSA, ISO, BSC, T47 and many more). The other threaded option is Italian… we don’t talk about them much, but they still thread in, but both threads go the same way. Simply put, for an English bottom bracket, the non-drive (left) side uses a standard right-hand thread (tightens clockwise), while the drive (right) side uses a reverse left-hand thread (tightens counter-clockwise). 

Inside both these ‘main’ categories are subcategories, however, only certain frame manufacturers do these. Trek, Cervelo, Specialized, Cannondale are a few are manufactures that use a ‘main’ category but add their own spin on it - just to make it even more confusing! If you're ever unsure, these manufacturers tend to have it on their websites.  

Frame width determines the bottom bracket width too! This is super important so you don’t accidentally buy a MTB bottom bracket for a road frame!

Check out this cheat sheet for bottom bracket standards

Question 2: Which drivetrain are you running?

Even easier, right? 

Well this one actually is, as most people are running either SRAM or Shimano.

Shimano has a 24mm spindle. That is it. Easy as, get the right bottom bracket and throw it all on there and you will be riding by the afternoon. This spindle diameter does not change between MTB and Road.

SRAM used to have two spindle options: GXP and DUB, but DUB is now the norm. If you opened a SRAM bottom bracket or crankset box you would see SRAM DUB30. No, the spindle is not exactly 30mm but it is actually 28.99mm. We round up for ease. 

Other crank brands will use either a Shimano or SRAM interface, making it easier for customers to customise their bikes away from the main two headliners.