
Shimano BB91-42A Press Fit MTB Bottom Bracket
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 |
Product Information
Product Information
Shipping & Returns
Shipping & Returns
Description
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 |













