The Shimano SM-BB91-42A is a professional XTR-level press-fit bottom bracket designed for HollowTech II MTB cranksets. The cups are constructed from a fiber-reinforced polymer, which significantly reduces the potential for creaking and prevents damage to high-end frames.
This maintenance-free assembly features advanced sealing to keep out water and grit, ensuring smooth rotation in the worst trail conditions. It is compatible with both 89.5mm and 92mm shell widths, utilizing a 42mm cup diameter for a secure and easy press-fit installation.
Quick Facts
| Feature |
Specification |
| Quality Level |
XTR (Mountain) |
| Crank Standard |
Shimano HollowTech II (24mm) |
| Shell Compatibility |
89.5mm / 92mm |
| Cup Diameter |
42mm |
| Material |
Fiber-Reinforced Polymer |
| Included |
L & R Cups, 2.5mm Spacer |