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Bottom bracket and frame standards, one hub

Bike-frame standards describe the frame, not the part you bolt to it. This hub gathers every threaded and pressfit shell reference and the comparison guides that explain how they differ, so you can name your frame's standard and find the exact bottom bracket.

Start with threaded or pressfit

The first split is whether the shell has machined threads or a smooth pressed bore. Threaded shells (BSA, Italian, T47) screw their cups in and are the most serviceable. Pressfit shells (PF30, BB30, BB86, BB92 and the rest) press bearings or cups into a smooth bore for a wider, stiffer frame. The comparison guides below explain each family.

If you are not sure which your frame is, measure the bore diameter and the shell width, because those two numbers name almost every standard.

Threaded shell references

The threaded standards covered here, each with dimensions and the cranks it hosts:

BSA / English: 1.37 in x 24 tpi, 68 or 73 mm, reverse-threaded drive side.

Italian: 36 mm x 24 tpi, 70 mm, right-hand both sides.

T47: 47 mm x 1 mm pitch, houses 30 mm bearings in a threaded shell.

Pressfit shell references

The pressfit standards covered here, by bore and width:

PF30: 46 mm bore, pressed cups, 30 mm spindle.

BB30: 42 mm bore, bearings direct in frame, 30 mm spindle.

BB86 and BB92: 41 mm bore, 24 mm spindle, road and mountain widths.

BB386EVO: 46 mm bore, 86.5 mm wide, long 30 mm spindle.

Comparison guides

The guides that answer the common comparison questions:

PF30 vs BB30: same spindle, different frame interface.

BB86 vs BB92: one standard, two widths.

T47 vs BSA: threaded, but wide enough for 30 mm.

Thread direction: which way a bottom bracket unthreads.

Related

Sources: Park Tool: Bottom Bracket Standards · Wheels Manufacturing bottom bracket fitment reference · BikeGremlin: Bottom bracket standards explained