The SHIMANO BB-UN300 is a high-quality square-taper bottom bracket with sealed cartridge bearings, designed to ensure reliable and smooth power transfer in city bikes, trekking bikes and MTBs. It is the ideal replacement part for those seeking a durable component offering excellent value for money.
Reliable sealed-cartridge design and smooth rotation
Thanks to the use of sealed industrial-grade bearings, the bottom bracket ensures quiet, smooth operation and high resistance to dirt, water and harsh weather conditions. The chainline stabiliser ensures precise drivetrain guidance, reducing wear on the crankset components.
Aluminium cup and secure mounting
The bottom bracket is fitted with a lightweight aluminium adapter, which ensures a secure fit within the frame cup without the risk of play or unwanted squeaking. The BSA thread standard guarantees broad compatibility and trouble-free installation in most classic bicycle frames.
Specifications:
| Manufacturer | SHIMANO |
| Model | BB-UN300 |
| Crank mounting type | Square (Square Taper) |
| Bottom bracket shell width | 73 mm (BSA) |
| Axle length | 118 mm |
| Thread | BSA (English / standard) |
| Adapter material | Aluminium |
| Package contents | Bottom bracket set (excluding crank mounting bolts) |
| Packaging type | Single pack (BOX) |
