BSA / English Threaded Bottom Bracket Compatibility

Also known as: BSC, English, ISO, 1.37" x 24 TPI

BSA (also called English or BSC) is the most common threaded bottom bracket standard on road, gravel and mountain bikes. The frame shell is threaded 1.37" × 24 TPI and comes in 68mm (road) or 73mm (MTB) widths. The drive-side cup is reverse-threaded, which stops it unscrewing as you pedal.

Because the cups thread directly into the frame, BSA is prized for being creak-free and serviceable — there is no bearing pressed into the frame. Nearly every crank spindle is catered for through the choice of BB: 24mm Shimano Hollowtech II, SRAM GXP and DUB, 30mm, and Campagnolo all have BSA-threaded options.

BSA at a glance

Fitment
threaded
Shell
34.8mm shell, 1.37" × 24 TPI thread
Shell width
68mm / 73mm
Native crank
24mm (Shimano Hollowtech II)
Good to know: The drive-side (right) cup is left-hand threaded — turn it clockwise to remove.

BSA bottom brackets by crank fitment

A BSAframe accepts different cranks depending on the bottom bracket you choose. Pick the group that matches your crankset's spindle.

For Campagnolo Ultra-Torque (25mm) cranks (3)

Fits: Campagnolo Ultra-Torque cranksets (two-piece, split 25mm axle).

For FSA MegaExo (19mm) cranks (2)

Fits: FSA MegaExo 19mm-spindle road cranksets.

For Campagnolo Power-Torque (25mm) cranks (1)

Fits: Campagnolo Power-Torque cranksets (one-piece 25mm axle).

For Square taper (ISO) cranks (1)

Fits: Square-taper ISO cranks (older Campagnolo and some European cranks).

Frames with a BSA bottom bracket

234 frames in our catalogue use the BSA standard.

Showing 48 of 234.

Cranksets that fit a BSA frame

These cranksets match a spindle standard a BSA bottom bracket supports.

Showing 24 of 60.

Frequently Asked Questions

Is a BSA bottom bracket threaded or press-fit?

BSA is a threaded standard: the cups screw directly into the frame (34.8mm shell, 1.37" × 24 TPI thread). Threaded shells are generally the most creak-free and serviceable, because no bearing is pressed into the frame itself.

What shell width does a BSA frame use?

BSA frames use a 68mm / 73mm shell (34.8mm shell, 1.37" × 24 TPI thread). Always match your bottom bracket to both the standard and your frame's exact shell width before buying.

Which cranks fit a BSA frame?

With the right bottom bracket, a BSA frame can run cranks on several spindle standards. In our catalogue we have BSA bottom brackets for: 24mm (Shimano Hollowtech II); 30mm (BB30 / PF30 / 386EVO); Square taper (JIS); SRAM GXP (24/22mm); SRAM DUB (28.99mm); Campagnolo Ultra-Torque (25mm); FSA MegaExo (19mm); Campagnolo Power-Torque (25mm); Square taper (ISO). Pick the bottom bracket that matches your crank's spindle — most commonly 24mm (Shimano Hollowtech II).

How many BSA bottom brackets and frames are listed?

We currently track 68 BSA bottom brackets and 234 frames built to the BSA standard, checked against our compatibility engine.

Other bottom bracket standards

T47ItalianPF30BB86BB92BB386EVOBBright

Compare standards

Not sure it fits?

Add your frame, crank and bottom bracket to a build and we'll check the shell, thread and spindle automatically.

Open the Builder

68 BSA bottom brackets checked by our compatibility engine.