T47 Bottom Bracket

T47 is a threaded bottom bracket standard with a 47mm shell diameter — wider than the traditional BSA/English standard (which uses a smaller shell).

The wider shell allows a larger spindle (commonly 30mm) without giving up the reliability and serviceability of threaded cups. T47 has become popular on modern frames that want the stiffness of press-fit standards with the fewer creak issues of threaded systems.

Common variants include T47 internal-bearing and T47 external-bearing designs; they are not always interchangeable. Always confirm your frame's exact T47 variant before buying.