Chains
Cycling · 10 specs
Direct Answer
Bicycle roller chains are standardized under ANSI B29.1 and ISO 9633. Across all modern bicycles, the chain pitch (distance between consecutive pin centers) is strictly 1/2 in (12.7 mm). Drivetrain speeds (1-speed to 13-speed) differ in internal roller width (1/8" for single-speed down to 11/128" for 11/12/13-speed) and external pin length (tapering from 8.6 mm on 1-speed to 5.25 mm on 12-speed chains).
Source: ISO 9633 (Cycle chains–Characteristics and test methods) / ANSI B29.1 · Last reviewed Aug 28, 2026
Specs
| Chain Pitch (All Speeds) | 12.70 mm (0.500 in / 1/2 in pin-to-pin pitch universal) |
| Single-Speed (1s / BMX / Track) Inner Width | 3.18 mm (1/8 in / 0.125 in roller width) |
| Single-Speed External Pin Length | 8.60–9.40 mm |
| 6/7/8-Speed Inner Width | 2.38 mm (3/32 in / 0.0938 in roller width) |
| 6/7/8-Speed External Pin Length | 7.10–7.30 mm |
| 9-Speed External Pin Length | 6.50–6.70 mm |
| 10-Speed External Pin Length | 5.88–6.10 mm |
| 11-Speed External Pin Length | 5.50–5.65 mm |
| 12-Speed External Pin Length (Shimano / SRAM) | 5.15–5.30 mm (e.g. SRAM Flattop / Shimano HG+) |
| Maximum Wear / Elongation Threshold | 0.5–0.75 % elongation (replace at 0.5% on 11/12-speed to save cassette) |
Chain Width Evolution Across Cassette Cog Densities
- Constant 1/2" Pitch with Shrinking Outer Width: As rear cassettes advanced from 5-speed freewheels (cog pitch 5.5 mm) to 12-speed cassettes (cog pitch 3.65 mm), the overall width of the chain shrank by over 35% (from 7.3 mm to 5.2 mm) to fit within tight cog spacing while maintaining the universal 12.7 mm pin pitch.
- 0.5% Wear Limit: Chain 'stretch' is caused by microscopic wear on the internal pins and bushings. Replacing a chain at 0.5% wear on 11- and 12-speed systems prevents premature shark-tooth wear on expensive titanium and steel cassette cogs.