Bottom bracket types

The most popular sealed bottom bracket systems

• Square taper: Outdated system that is now hardly ever used. The crank arms are fitted onto the ends of a square spindle and tightened by bolts which screw into the spindle on both sides.

• Octalink and ISIS: Older, and now seldom used system. The crank arms are connected to the ends of a spindle with 8 teeth (10 teeth with ISIS).

The most popular sealed bottom bracket systems with separate bearing cups:

• Shimano-BB (for Hollowtech II cranks): The current standard system for screwed non-sealed Shimano bearings. Spindle is fixed to right crankarm, spindle is 24mm in diameter.
These cranks fit both BSA threaded or Pressfit (86,5/92mm) frames.

• SRAM DUB: SRAM standard with 28,99mm spindle. One spindle for BSA and pressfit. Only cups need to be changed.


Frame BB

• BSA thread: Used mainly for screwed non-sealed bearings

• Press fit BB 86.5: Bearing cups without threads are pressed into the bottom bracket shell using plastic adapters. The spindle diameter is approx. 24mm. This is the most popular press fit bearing standard for road bikes. Housing width: 86.5mm.

• Press fit BB92: Bearing cups without threads are pressed into the bottom bracket shell using plastic adapters. The spindle diameter is approx. 24mm. This is the most popular press fit bearing standard for mountain bikes. Housing width: 92mm.

• There are other press fit bearing standards, which have not as yet established themselves.