Bottom Brackets

Bottom Bracket Buying Guide

The bottom bracket is a pair of bearings that your crankset spindle rotates in. It's a simple job done by a complicated mess of standards — more than any other component, the bottom bracket requires you to know exactly what your frame and crankset need before buying.

The Standards

BSA/English threaded (68mm or 73mm shell, 1.375" x 24 TPI threads) — the oldest and most reliable standard. The shell is threaded, so the BB screws in. No creaking when properly installed. Shimano, Hope, Chris King and Wheels Manufacturing all make excellent threaded BBs. Press-fit BB92 (also called PF41) — 41mm bore, 89.5 or 92mm shell width. The cups press into the frame without threads. Common on mid-range to high-end frames. Prone to creaking if tolerances are loose. PF30 — 46mm bore, 68mm shell. Used by some Cannondale and other brands. T47 — a newer standard that combines press-fit shell dimensions with threads. Growing in popularity because it solves press-fit creaking problems.

Spindle Compatibility

The BB must match your crankset's spindle diameter. Shimano Hollowtech II uses a 24mm spindle. SRAM DUB uses a 28.99mm spindle. Race Face Cinch uses a 30mm spindle. Hope and others use 30mm. A DUB BB won't work with a Shimano crankset — the bearing bore is wrong. This is the most common mistake when buying a bottom bracket.

Press-fit Problems

Press-fit BBs are notorious for creaking. The root cause is frame shell tolerances — if the bore is even slightly oversized, the cups move under load and creak. Solutions: Loctite 641 (retaining compound) on the cups during installation, or thread-together BB kits from Wheels Manufacturing and Hope that clamp through the frame like a threaded BB. If your frame has a press-fit shell and you're sick of creaking, a thread-together conversion kit is the permanent fix.

Bearing Quality

BB bearings are cheap to replace — most BBs use standard cartridge bearings (6805 or 6806 series) that cost £5-10 per pair. Premium bearings from Enduro, CeramicSpeed and SKF last longer but cost significantly more. For most riders, replacing standard bearings annually is more cost-effective than running ceramic bearings. Hope and Chris King BBs are fully serviceable — you can replace just the bearings and seals rather than the entire unit.