Road riders with a threaded BSA frame and a Shimano Hollowtech II crankset.
The Shimano BB-RS501 is a Hollowtech II external-cup bottom bracket for frames with a 68 mm BSA (English) threaded shell, the most common threaded standard on road bikes.
It takes a 24 mm spindle, so it fits Shimano's two-piece road cranks from Sora and Tiagra up through 105, Ultegra and Dura-Ace. Shimano gave it a new seal design over the older RS500 to keep water and grit out of the bearings for longer.
When your cranks start to feel gritty or you hear a creak from the bottom bracket, fresh cups are an inexpensive fix that makes the whole bike feel smoother.
BSA 68 mm
The most common threaded road shell.
24 mm Hollowtech II
Fits Shimano two-piece road cranks.
Better seals
Updated sealing over the RS500.
Easy to service
Threaded cups remove cleanly for later replacement.
Bottom bracket
Improved seals
Shimano updated the sealing on the RS501 over the RS500 for longer life in wet and dirty conditions.
Hollowtech II
External bearing cups that suit Shimano's 24 mm two-piece road cranksets.
Great for
Maybe not for
Check your frame has a 68 mm BSA threaded shell. BSA cups are marked 1.37 x 24; Italian shells need the separate ITA model.
Fitting tips
Grease the threads, remember the drive-side cup is reverse threaded on BSA, and torque the cups with a proper Hollowtech II cup tool. Any creak afterwards is often dry threads or crank preload, so bring it in if it won't go away.
