How do I tell which bottom bracket standard my frame uses?
By Crankworthy · Published · Updated
Look at the shell first: if the bottom bracket screws in, the frame is threaded (most often BSA, 68 or 73mm wide); if the cups or bearings are pressed into a smooth shell, it is a press-fit standard. Then measure the shell width, and for press-fit the inside diameter, to name it exactly.
The numbers
| BSA (English), threaded | 1.37″ × 24 tpi, ~33.7 mm bore |
|---|---|
| BSA shell widths | 68 or 73 mm |
| T47, threaded | M47 × 1.0, ~46 mm bore |
| BB86 / BB92 (PF41), press-fit | 41 mm bore |
| BB30 (PF42), press-fit | 42 mm bore |
| PF30 (PF46), press-fit | 46 mm bore |
Where on your bikeBottom bracket shell, between the cranks
The main families
Threaded BSA (also called English) is the most common: the cups screw into a shell threaded 1.37″ × 24 tpi, and the drive-side cup has a left-hand thread [1]. The shell is 68 or 73mm wide [2]. T47 is a larger threaded shell, about 46mm inside, and its drive side is left-hand threaded too [1].
Press-fit shells are a smooth bore with no threads [1]; the bearings, or cups holding them, are pressed in. They are named by that bore: PF41, sold as BB86 and BB92 (the number is the shell width), BB30, also called PF42, and PF30, also called PF46 [1].
T47 and PF30 share the same 46mm bore [1] — only the threads tell them apart, so look before you buy.
The shell standard and the crank spindle are separate questions. A 24mm Shimano spindle or a 28.99mm SRAM DUB spindle can each fit several shell types — the bottom bracket is the part that adapts one to the other.
How to identify yours
- Threaded
- External cups sit outside the shell with tool notches around their edge, or a cartridge sits inside with a splined end. Either way, it unscrews.
- Press-fit
- Cups sit flush with, or inside, a smooth shell and have no notches for a threaded tool. They are removed with a drift or a press-fit extractor.
- Measure the width
- With the cups out, measure straight across the shell. It will read very close to a standard number such as 68, 73, 86.5 or 92mm.
- Measure the bore (press-fit)
- Measure the inside diameter: about 41mm is PF41 (BB86/BB92), 42mm is BB30, 46mm is PF30 [1].
- Check the frame spec
- The manufacturer's spec sheet usually names the standard outright.
Skip
- Don’t buy: a bottom bracket chosen by the crank alone
- Instead: match it to both your shell standard and your crank’s spindle.
What real bikes use
From our research, the bottom bracket standard each maker lists for these bikes.
- 2024 Cannondale CAAD13 Disc 105 — BB30 / PF30 maker’s spec page
- 2024 Cannondale Synapse 1 — BB30 / PF30 maker’s spec page
- 2024 Cannondale Synapse 2 — BSA threaded maker’s spec page
- 2024 Cannondale Synapse 3 — BSA threaded maker’s spec page
- 2024 Cannondale Synapse Carbon 2 LE — BSA threaded maker’s spec page
- 2024 Cannondale Synapse Carbon 3 L — BSA threaded maker’s spec page
- 2024 Cannondale Synapse Carbon 4 — BSA threaded maker’s spec page
- 2024 Cannondale Trail 5 — BSA threaded maker’s spec page
If your press-fit bottom bracket creaks
- Thread-together bottom brackets
- You cannot cut threads into a press-fit shell, but thread-together bottom brackets replace the pressed cups with two halves that screw into each other inside the shell. They are a common cure for press-fit creaking. Match one to your shell standard and crank spindle.