Condensed Answer: Chainrings are less “pretentious” when it comes to chain size than cassettes. A 12-speed chainring can operate with a 10-speed chain if the rest of the drivetrain is also designed for 10 speeds.
Chain Width Depends On The Number of Speeds
A chain has inner and outer width. The inner width is the distance between the inner plates whereas the outer width is the distance between the outer plates.
The inner width of a chain stays the same or changes very little with each gear increase.
This is necessary because the thickness of cassette sprockets remains the same or close to it regardless of the gear number.
However, the outer width of the chain has to decrease with each gear increase because the cog pitch of the cassette gets smaller when there are more gears. (The cog pitch is the center-to-center distance between each cassette cog.)
The distance between the cogs decreases with each gear increase so that the same hub can accept a wide range of cassettes.
The decreased distance requires a chain with a narrower outer width. Since the inner width of the chain cannot be reduced, the only option is to reduce the thickness of the outer plates. Hence why chains designed for more gears have thinner outer links.
The decreased outer width of the chain makes it possible to use a chain designed for more speeds on a cassette with fewer cogs (e.g., using a 10-speed chain on an 8-speed cassette.) The opposite, however, is not possible because the chain will be too wide and will rub against the cogs surrounding the gear that’s currently in use.
Chain and Chainring Compatibility
The requirements for chain and chainring compatibility are:
- The inner width of the chain shouldn’t be too narrow for the chainring. If that condition is not met, the chain will bind against the chainring.
The table below contains the inner and outer width of 7 to 12-speed chains:
| Number of Speeds | Inner/Roller Width | Outer width |
| 7 | 2.38mm | 7.3mm (Shimano), 7.1mm (SRAM) |
| 8 | 2.38mm | 7.3mm (Shimano), 7.1mm (SRAM) |
| 9 | 2.18mm | 6.5-7mm |
| 10 | 2.18mm | 5.88-6mm |
| 11 | 2.18mm | 5.5-5.6mm |
| 12 | 2.18mm | 5.3mm |
The inner width of 10 and 12-speed chains is the same. 12-speed chains, however, are 0.3mm narrower overall due to their thinner outer plates.
The inner width of a 10-speed chain is sufficient to accept a standard 12-speed chainring.
If the bike has a 1x drivetrain (single chainring), then the combination of a 10-speed chain and a 12-speed chainring will more than likely succeed.
It’s also worth mentioning that 12-speed cassettes are not compatible with 10-speed chains. A 10-speed chain is simply too wide for 11 and 12-speed cassettes.
Front Derailleur Compatibility
If the bike has multiple chainrings, then the front derailleur could create issues. The cages of front derailleurs have to reflect the chain width changes too.
For example, the cage of a derailleur designed for 8-speed chains will be wider than that of a derailleur made for 12-speed chains. If such a derailleur is used on a 12-speed system, the shifting will be subpar due to the gap between the outer plates of the chain and the derailleur cage’s walls.
If a 10-speed chain is used with a front derailleur designed for a 12-speed chainring, the user will experience the opposite effect – the derailleur’s cage will be narrower than needed. The result will be the rubbing of the chain against the cage of the derailleur. To what extent this will manifest, depends on the particular drivetrain.
When is the 10-speed chain + 12-speed chainring combination viable?
A 10-speed chain is not compatible with a 12-speed cassette. Consequently, a 10-speed chain cannot be integrated into a 12-speed drivetrain.
Therefore, the only option left is to integrate the 12-speed chainring into a 10-speed drivetrain (10-speed cassette + 10-speed chain+10-speed shifter).
In that context, the combination will work normally if the drivetrain operates with a single chainring. If the drivetrain has multiple chainrings and a front derailleur, some problems are expected.
If the front derailleur is built for a 12-speed chain, then some rubbing between the derailleur’s cage and the chain is expected.
If the front derailleur is built for a 10-speed chain, however, the shifting is expected to be decent.
