SHIMANO Bottom Bracket BB-UN300 BSA 73mm 122.5mm Without Fixing Bolt

The SHIMANO Bottom Bracket BB-UN300 is designed to deliver reliable performance, smooth pedaling efficiency, and long-lasting durability for everyday cycling and performance riding needs. Built with Shimano’s trusted engineering quality, this bottom bracket provides a stable and consistent drivetrain experience while reducing unwanted movement and friction during riding. The BB-UN300 features a strong sealed cartridge design that helps protect internal components from dust, dirt, and moisture, allowing riders to enjoy dependable operation in different riding conditions. With a BSA threaded 73mm shell compatibility and a 122.5mm spindle length, it is suitable for selected crankset setups and bicycle configurations. Whether you are upgrading an existing drivetrain or replacing a worn-out bottom bracket, the Shimano BB-UN300 offers durability, smooth rotation, and dependable performance for daily rides, touring, and recreational cycling.

Key Features

• Brand: Shimano

• Model: BB-UN300

• Bottom Bracket Type: Sealed cartridge bottom bracket

• Shell Compatibility: BSA threaded

• Smooth Rotation: Designed for stable and efficient pedaling

• Durable Construction: Built for long-lasting use

• Protected Internal Bearings: Helps resist dirt and moisture entry

• Low Maintenance: Sealed design reduces maintenance requirements

• Reliable Performance: Suitable for daily and long-distance riding

Product Specifications

• Product Name: SHIMANO Bottom Bracket BB-UN300

• Shell Width: 73mm

• Spindle Length: 122.5mm (LL123)

• Thread Type: BSA Threaded

• Fixing Bolt Included: No

• Compatibility: Compatible with selected Shimano cranksets and compatible systems

• Construction Type: Sealed cartridge unit

• Application: Road, MTB, hybrid, and general bicycle use

Bottom Bracket Performance & Durability

The Shimano BB-UN300 is built with a sealed internal structure that improves bearing protection and helps maintain smoother crank movement over extended use. Its construction reduces contamination from external elements and supports consistent pedaling performance. The strong design also helps reduce unwanted play, vibration, and drivetrain inefficiencies during rides.

Easy Operation / Usage

• Remove the old bottom bracket from the bicycle frame

• Confirm frame shell width and spindle compatibility before installation

• Install the BB-UN300 into the BSA threaded frame shell

• Tighten according to recommended specifications

• Install the crankset and check for smooth rotation before riding

Why Choose This Product

• Genuine Shimano quality and reliability

• Smooth and efficient pedaling performance

• Durable sealed cartridge construction

• Reduced maintenance requirements

• Suitable for multiple bicycle applications

• Long-lasting design for regular use

• Trusted replacement and upgrade option

In the Box

• 1 x SHIMANO BB-UN300 Bottom Bracket