Shimano UN300 Square Taper Bottom Bracket

The Shimano UN300 Bottom Bracket is the most popular square taper bottom bracket at Crows by far! Shimano has been producing bottom brackets in this standard for decades and they have proven to be high quality and very long lasting in all iterations. It is not uncommon for us to see one of these ridden hard, year after year, and still running damn smooth! This bottom bracket is a sealed cartridge with non-replaceable bearings. This product includes crank bolts (requires 14mm metric socket/wrench for crank arm installation.)

Available for BSA (1.37 x 24 thread pitch,) threaded bottom bracket shells in 68mm and 73mm.

*Consult your crank manufacturer for spindle length recommendations to get the correct chainline. If there is no manufacturer recommend spindle length unfortunately you are going to have to make your best guess because there is no standardized placement of the chainring on vintage cranks. Best of luck! 

**The UN300 replaces the UN26 and the UN55 as the sole square taper bottom bracket option from Shimano.