Is T47 the same as BSA, just bigger?

Both are threaded standards, but they're different sizes: BSA threads into a 68mm or 73mm shell at 1.370" x 24 TPI, while T47 threads into a wider, larger-diameter shell (46mm bore). They are not interchangeable — a frame is machined for one or the other.

Can I put a BSA bottom bracket in a T47 frame?

No. The shell diameters don't match — BSA cups are sized for a narrower bore than a T47 shell. You need a bottom bracket made specifically for T47.

Why do some frames use T47 instead of BSA?

T47's larger shell diameter gives frame designers more room to route internal cables and hoses through the bottom bracket area, and its wider bore accepts a broader range of crank spindle standards (24mm, 30mm, GXP, DUB) using the correct bearing cups, without needing a press-fit shell.

Does T47 solve the creaking problems press-fit bottom brackets are known for?

That's a large part of its appeal — because it's threaded like BSA, it avoids the interference-fit tolerances that press-fit standards depend on, which is a common source of creaking. It keeps a threaded standard's reliability while accepting a wider range of crank spindle sizes.

Compatibility guide

T47 vs BSA bottom brackets: two threaded standards, not one

Both T47 and BSA are threaded bottom bracket shells — which means both avoid the press-fit creaking problem — but they're different diameters and aren't interchangeable with each other.

The short answer

A frame is machined for exactly one bottom bracket shell standard, and the shell itself can't be converted from one to the other — T47's bore is significantly wider than BSA's. What decides your bottom bracket purchase is your frame's shell standard, not your crankset brand: both T47 and BSA bottom brackets are available to fit most common crank spindle diameters (24mm Shimano-style, 30mm, SRAM GXP, SRAM DUB), you just need the cups made for your frame's actual shell.

The specs

Spec	T47	BSA
Type	Threaded	Threaded
Shell bore	46mm (wide)	Narrower — sized for 1.370" threading
Common shell widths	68mm, 73mm, 85.5mm, 90mm, 100mm	68mm (road), 73mm (mountain)
Thread direction	Non-drive side reverse-threaded, like BSA	Non-drive side reverse-threaded (self-tightening)
Crank spindle support	Wide bore fits more spindle standards with the right cups	Narrower bore limits which spindle sizes fit without an adapter
Cable routing	More room for internal routing through the shell	Tighter clearance

Where it breaks

A T47 bottom bracket will not thread into a BSA shell, and a BSA bottom bracket cannot be forced into a T47 shell — the bore diameters are different, not just the thread pitch.
Shell width (68/73mm for BSA; 68/73/85.5/90/100mm for T47) is a separate spec from the bore standard — you need both the correct family (T47 or BSA) and the correct width for your frame.
A crankset spindle standard (24mm, 30mm, GXP, DUB) is a separate compatibility question from the shell standard — the bottom bracket cups bridge between the two, so the cups need to match both your frame's shell and your crank's spindle.

Practical takeaways

Check your frame, not your crank, first: the frame's bottom bracket shell decides whether you need T47 or BSA hardware — that's fixed by the frame and can't be changed.
Buying a new crankset: as long as you get bottom bracket cups matched to your frame's shell and your crank's spindle diameter, most modern cranksets work in either shell family.
Creaking bottom bracket: if you're replacing a press-fit setup and have the option, both T47 and BSA avoid the tolerance-stack creaking that press-fit shells are prone to — but switching shell standards means a new frame, not just new bearings.

Check a specific pairing

Got a specific part number in mind? Drop it into the compatibility checker for a verdict with reasoning, or spec a full build in the planner.

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