T47 Inboard bottom bracket
T47 Inboard is a threaded standard: the bottom bracket shell has an internal thread, so the bottom bracket screws straight into the frame. You recognise a T47 Inboard frame by a shell 85.5 mm wide with an inner diameter of 46 mm (T47 thread).
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Sizes of a T47 Inboard bottom bracket shell
85.5 mm
Shell width
46 mm (T47 thread)
Inner diameter
threaded
Inside of the shell
Frequently asked questions
CEMA has T47 Inboard bottom brackets for Shimano, SRAM DUB, SRAM GXP, FSA386/Rotor/Raceface 30mm and PRAXIS M30 cranksets.
Measure the bottom bracket shell: on T47 Inboard it is 85.5 mm wide, with an inner diameter of 46 mm (T47 thread).
Both frame types use a T47 thread. The difference is the width of the frame, which puts the bearings of the bottom bracket either inside the frame (Inboard) or outside it (Outboard). A T47 Inboard shell is 85.5 mm wide, with an inner diameter of 46 mm (T47 thread). A T47 Outboard shell is 68 or 73 mm wide, with an inner diameter of 46 mm (T47 thread). More about T47 Outboard →
A T47 Inboard shell is 85.5 mm wide, with an inner diameter of 46 mm (T47 thread). A T47A shell is 77 mm wide, with an inner diameter of 46 mm (T47 thread), and is asymmetric on the non-drive side. T47A is used mainly on road bikes and certain gravel bikes. More about T47A →
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