Steel axle, cartridge bearings
The main criterion for this Shimano BB-UN300 bottom bracket is its extended service life.
Road specialist
Shimano ’s BB-UN300 bottom bracket (part no. EBBUN300KB27X) is a reliable and cost-effective solution for bikes fitted with a square-axle crankset. Designed for frames with a BSA-standard threaded bottom bracket (68 mm), it offers excellent strength and enhanced durability, making it ideal for everyday use on road bikes, mountain bikes or city bikes.
Featuring a 127.5 mm JIS square taper spindle, this model is particularly suited to triple cranksets or older systems Shimano. Its sealed cartridge design with steel bearings ensures smooth rotation whilst minimising maintenance. Thanks to its sturdy steel and aluminium construction, it effectively withstands mechanical stress and outdoor conditions.
Versatile and easy to install, the BB-UN300 is an excellent choice for replacing a worn bottom bracket whilst maintaining stable and efficient pedalling.
Key features:
threaded bottom bracket cup BSA-style frame mounting 1.37x24
Square taper axle length 127.5mm
Supplied with crank bolts
| Bottom bracket | BSA 1.37x24 |
|---|---|
| Crankset compatibility | Shimano square axle |
| Bearings | steel |
| EAN | 4550170619176 |
| Supplier reference | EBBUN300KB27X |
This is a classic standard where the cranks are attached to a square-section axle (JIS), which is very common on entry-level and mid-range bikes.
It is compatible with BSA threaded frames (68 mm) and square-axle cranksets only.
This length is generally used for triple cranksets to ensure the chain runs correctly.
Yes, it’s designed for versatile use: city cycling, touring, mountain biking or road cycling.
No, thanks to its sealed bearings, it requires virtually no maintenance.
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