Shimano Hollowtech II Bottom Brackets

Shimano offers various bottom brackets primarily using the Hollowtech II system (external bearings and a 24mm spindle) in both threaded and press-fit configurations to fit different frame types.
Other systems like Square Taper and Octalink are also available for older or entry-level components.

Common Shimano Bottom Bracket Types

The type of bottom bracket you need is determined by your bike's frame and crankset. Shimano predominantly uses its Hollowtech II design across most modern groupsets.
Hollowtech II: This is Shimano's main system, featuring an integrated 24mm spindle attached to the right crank arm and external bearings (for threaded) or pressed-in cups with internal bearings (for press-fit). This design is widely praised for its optimal balance of stiffness, strength, and light weight.
Square Taper: An older, cartridge-style system where the crank arms attach to a square spindle. The Shimano BB-UN300 is a common model in this category, known for its reliability and durability.
Octalink: Predecessor to Hollowtech II, this system uses a splined interface between the crank and the bottom bracket spindle for a more rigid connection than square taper. The Shimano BB-ES300 is a popular Octalink bottom bracket.