Road bottom brackets

How to choose a road bottom bracket

The bottom bracket connects the frame to the crankset. You therefore need to choose it based on two dimensions: the frame standard and the crank spindle diameter. Get either one wrong and nothing will fit.

The frame standard

• BSA / BSC : threaded bottom bracket, 68 mm for road bikes, with English threading. The easiest to maintain, and one that has made a strong comeback in recent years.
• Italian : also threaded, 70 mm, but with a different thread pitch. Found on older Italian frames.
• Press Fit : press-fit cups, without threads — BB86 and 86.5, PF30, BB386EVO, BB30, BBRight. Lighter, but more prone to creaking.
• T47 : threaded, but with a Press Fit diameter. A more recent compromise, available in internal or external versions.

The crank spindle diameter

• 24 mm : Shimano Hollowtech II and most compatible cranksets.
• 28.99 mm : SRAM DUB.
• 30 mm : Rotor, FSA 386EVO, Praxis.
• Ultra-Torque : Campagnolo, with a half-spindle and its own bearing on each crank arm.
• A crankset with a 30 mm spindle will not fit a bottom bracket designed for 24 mm: you need the matching bottom bracket or an adaptor such as the Rotor BB4224.

The bearings can be replaced separately

On many bottom brackets, only the bearings are worn, and they are sold separately in steel or ceramic. Ceramic bearings spin a little more freely but cope less well with water and spray: on a bike ridden year-round, a good steel bearing lasts longer.

Before deciding it needs replacing

A creaking bottom bracket does not always need replacing. Check, in order, the crank bolt torque, then whether the contact surfaces are clean and greased, and only then the bearings for wear. On a Press Fit, just a few hundredths of a millimetre of play in the frame can cause noise — which is why many cyclists switch back to threaded bottom brackets.

To find out more: How to choose a road bike crankset

See also: Road cranksets and crank arms · Road bearings · Road drivetrain spares