British Standard Cycle Threads
British Standard Cycle is a British Imperial screw thread standard.
British Standard Cycle is a British Imperial screw thread standard made for bicycle and motorcycle applications.
| Diameter (in) | TPI | Pitch (in) | Outside Diameter (in) | Core Diameter (in) |
|---|---|---|---|---|
| 1/4 | 26 | 0.0385 | 0.250 | 0.209 |
| 5/16 | 26 | 0.0385 | 0.3125 | 0.272 |
| 3/8 | 26 | 0.0385 | 0.3750 | 0.334 |
| 7/16 | 26 | 0.0385 | 0.4375 | 0.397 |
| 1/2 | 26 | 0.0385 | 0.5000 | 0.459 |
| 9/16 | 26 | 0.0385 | 0.5625 | 0.522 |
| 5/8 | 26 | 0.0385 | 0.6250 | 0.584 |
| 11/16 | 26 | 0.0385 | 0.6875 | 0.647 |
| 3/4 | 26 | 0.0385 | 0.7500 | 0.709 |
| 1 | 26 | 0.0385 | 1 | 0.959 |
| 1 3/8 | 24 | 0.0417 | 1.625 | 1.326 |
- TPI = threads per inch
- the thread angle is 60 degrees
The fine pitch allows high torque settings and is resistant to vibrations.
Note that the most commonly used bottom bracket thread today is 1 3/8" x 24 TPI.
