Fit a Shimano Hollowtech II (24 mm) crank in a Specialized OSBB shell
Whether a Shimano Hollowtech II (24 mm) crank fits a Specialized OSBB shell, and the bottom bracket that makes it work.
The crank and the shell
| Crank spindle | Shimano Hollowtech II (24 mm) (24 mm constant diameter) |
|---|---|
| Frame shell | Specialized OSBB (42 mm bore (alloy, BB30 style) or 46 mm bore (carbon, PF30 style), 68 mm (road) and 73 mm (MTB) wide) |
| Verdict | needs a reducer |
| Bottom bracket to buy | OSBB to 24 mm Shimano reducer bottom bracket |
SHELL Specialized OSBB (42 mm bore (alloy, BB30 style) or 46 mm bore (carbon, PF30 style), 68 mm (road) and 73 mm (MTB) wide)
SPINDLE Shimano Hollowtech II (24 mm) (24 mm constant diameter)
BB OSBB to 24 mm Shimano reducer bottom bracket
SPINDLE Shimano Hollowtech II (24 mm) (24 mm constant diameter)
BB OSBB to 24 mm Shimano reducer bottom bracket
A 24 mm Shimano crank runs in a Specialized OSBB shell using a reducer BB that presses into the 46 mm carbon or 42 mm alloy bore and steps the bearing down to 24 mm.
Match the reducer to the bore: a PF30-style reducer for a 46 mm carbon OSBB, a BB30-style reducer for a 42 mm alloy OSBB. The wrong one will not press cleanly.
The bottom bracket to buy
Search Amazon for OSBB to 24 mm Shimano reducer bottom bracketaffiliate searchFind OSBB to 24 mm Shimano reducer bottom bracket on eBayaffiliate
Related fits
Shimano Hollowtech II (24 mm)24 mm spindleSpecialized OSBB42 or 46 mm boreShimano Hollowtech II (24 mm) in a BSA / English threaded shelldrops inShimano Hollowtech II (24 mm) in a Italian threaded shelldrops inShimano Hollowtech II (24 mm) in a T47 external (T47-68 / T47-73) shelldrops inShimano Hollowtech II (24 mm) in a PF30 press fit shellneeds a reducer
SOURCES: Park Tool, Bottom Bracket Standards and Terminology · Wheels Manufacturing, Crankset Spindle Standards & BB Compatibility · Hambini Engineering, Specialized OSBB Engineering Guide · Kogel Bearings, Specialized OSBB explained