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Bottom Bracket Calculator — Find the Right BB
Find the right bottom bracket for your frame and crankset combination.
How We Calculate This
Bottom Bracket Compatibility
- BB shell determines the physical size and thread type
- Crankset determines the spindle diameter and BB interface
- The correct BB connects your frame shell to your crankset spindle
- Common spindle sizes: 24mm (Shimano), 28.99mm (SRAM DUB), 25mm (Campagnolo), 30mm (BB30)
Frequently Asked Questions
Measure the shell width (68, 73, 83, 86.5, 91.5 mm) and check if it is threaded or smooth bore. BSA threaded is by far the most common. Press-fit shells (BB86 = 86.5mm, BB92 = 91.5mm, both 41mm bore) are smooth inside.
BSA (English) uses 1.370" x 24 TPI with the drive-side cup having left-hand thread. Italian uses 36mm x 24 TPI with both sides right-hand thread. BSA is far more common worldwide.
Press-fit BBs can creak if not installed properly. Many cyclists prefer threaded standards (BSA or T47) for reliability. T47 is a newer threaded standard that fits press-fit shell bores.
A quality BB lasts 10,000-20,000 km depending on conditions. Replace when it feels rough, makes clicking noises, or has noticeable play. Clean and inspect annually.
Yes. BB compatibility depends on the frame shell and crankset spindle, not the groupset brand. Use the correct BB for your crankset spindle diameter and frame shell type.
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Last updated: February 2026
All calculations are estimates. Always verify results and consult a professional bike fitter where appropriate.