BSA / English threaded bottom bracket shell (1.37" x 24 TPI)
What a BSA / English threaded shell measures, which crank spindles it hosts, and the bottom bracket to buy.
Published dimensions
| Type | threaded |
|---|---|
| Shell inside diameter | 1.37 in (about 34.8 mm) threaded bore |
| Shell width | 68 mm (road), 73 mm (MTB), 83 mm and 100 mm (fat / DH) |
| Thread | 1.37 in x 24 TPI, drive-side cup left-hand (reverse) thread, non-drive right-hand |
| Crank spindles it hosts | 24 mm (Shimano Hollowtech II), 24/22 mm (SRAM GXP) and 28.99 mm (SRAM DUB) via the matching threaded BB |
SHELL 68 mm (road), 73 mm (MTB), 83 mm and 100 mm (fat / DH)
SPINDLE 24 mm (Shimano Hollowtech II), 24/22 mm (SRAM GXP) and 28.99 mm (SRAM DUB) via the matching threaded BB
SPINDLE 24 mm (Shimano Hollowtech II), 24/22 mm (SRAM GXP) and 28.99 mm (SRAM DUB) via the matching threaded BB
Used on: the long-standing threaded standard on road, gravel and MTB frames worldwide.
The drive-side cup is reverse-threaded, so it tightens anticlockwise. This is the most serviceable standard because the cups thread in and out rather than press, and creaks are usually cured by re-greasing the threads.
Fit a crank to this shell
Shimano Hollowtech II (24 mm) in a BSA / English threaded shelldrops inSRAM DUB (28.99 mm) in a BSA / English threaded shelldrops inSRAM GXP (24/22 mm) in a BSA / English threaded shelldrops inItalian threadedrelated shell (36 mm x 24 TPI)
SOURCES: Park Tool, Bottom Bracket Standards and Terminology · Wheels Manufacturing, BB Overall Width Reference Chart