A 9-speed bicycle chain has an outer width ranging from 6.5 to 6.7 mm.
When discussing bicycle chain "size," the most critical dimension for compatibility, especially with multi-speed drivetrains, is the chain's outer width. This measurement determines whether the chain will correctly fit between the cogs of your cassette and chainrings without rubbing or causing shifting issues.
Understanding Chain Outer Widths
The outer width of a bicycle chain is specifically designed to match the spacing of the cogs on the cassette. As the number of speeds (sprockets) on a cassette increases, the cogs become more closely spaced, requiring a narrower chain. Below is a general guide to the outer widths for common multi-speed bicycle chains:
| Number of Sprockets (Speeds) | Chain's Outer Width (mm) |
|---|---|
| 6 speed | 7.8 |
| 7 speed | 7.3 |
| 8 speed | 7.0 – 7.3 |
| 9 speed | 6.5 – 6.7 |
Note: While there might be slight variations between manufacturers, these ranges are standard.
Why Chain Width Matters
Using a chain with the correct outer width is crucial for the optimal performance and longevity of your bicycle's drivetrain. An incorrect chain width can lead to:
- Poor Shifting: A chain that is too wide for a higher-speed cassette (e.g., an 8-speed chain on a 9-speed system) will not fit properly between the cogs, leading to sluggish, inaccurate, or incomplete shifts.
- Chain Rub: It may rub against adjacent cogs or even the derailleur cage, causing unnecessary friction and noise.
- Increased Wear: Improper fit can accelerate wear on the chain, cogs, and chainrings.
- Dropped Chains: A chain that is too narrow for a lower-speed system (less common, but possible) might not engage the cogs effectively, potentially leading to chain drops.
For comprehensive information on selecting the right bicycle chain and understanding various dimensions, you can explore detailed bicycle chain buyer's guides.
