An 11-speed chain can technically be used in conjunction with an 8-speed cassette, but the combination is not recommended unless there is no other option to get the bike running again.
11-speed chains are simply too narrow, internally and externally, to be coupled with an 8-speed cassette without causing shifting latency.
If you have an 8-speed cassette, it’s recommended to get an 8/9-speed chain for it. Those are cheaper too.
If you have an 11-speed chain, you can pair it with 10/11-speed cassettes.
Why Are 11-speed Chains and 8-speed Cassette Incompatible?
The incompatibility is entirely due to the dimensions of each unit. The cassette sprockets are too thick whereas the cassette is too narrow externally and internally.
Bicycle chains have the following properties:
- Inner and Outer Width
Chains have an inner and an outer width. The inner width is the distance between the internal plates whereas the outer width is the distance between the external plates.
- Chain width changes according to the number of gears on the cassette
The inner chain width remains the same across 9/10/11/12-speed chains because the sprocket thickness of the respective cassettes changes very little.
The external width, however, decreases with each gear increase. This happens because cassette cogs get closer to one another with each gear jump. As a result, the chain has to get thinner or else it starts rubbing against the adjacent cogs.
This is achieved by making the external plates of the chain thinner. For that reason, chains designed for fewer speeds are stronger when all parameters such as build quality are the same.
The table below contains the outer and inner width of common bicycle 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 |
Conclusions
The inner width of 11-speed chains is 0.2mm less than that of 8-speed chains (8.772% difference).
The outer width of 11-speed chains is approximately 1.8mm less than that of 8-speеd chains (2.18% difference).
The next table contains the cog pitch (center-to-center distance between two cogs) and sprocket thickness of 7/8/9/10/11/12-speed bicycle cassettes:
| Number of Speeds | Cog Pitch | Sprocket Thickness |
|---|---|---|
| 8 | 4.8mm | 1.85mm |
| 9 | 4.35mm | 1.78mm |
| 10 | 3.95mm | 1.6mm |
| 11 | 3.9mm | 1.6mm |
| 12 | 3.55mm | 1.6mm |
Conclusions:
The cog pitch of 11-speed cassettes is 0.9mm narrower than that of 8-speed cassettes (20.69% difference).
The sprocket thickness of 11-speed cassettes is 0.25mm less than that of 8-speed cassettes (11.42% difference).
The dimensions of 11-speed chains create the following issues when using an 8-speed cassette:
- Shifting latency
11-speed chains are much narrower than 8-speed models. Also, there’s a fairly large discrepancy between the cog pitch of an 11-speed and an 8-speed cassette. As a result, the derailleur has to travel significantly more to reach the chain and move it onto the desired cog. The outcome is slow and “weird” shifting.
- Loss of flexibility
8-speed sprockets and chainrings could cause some binding due to the narrower internal width. In other words, there simply isn’t enough space for the sprocket/chainring to feel free. The chain will lose its flexibility and thus negatively affect the shifting performance of the bike.
What should I do?
It doesn’t make a lot of sense to use an 11-speed chain in conjunction with an 8-speed cassette unless that’s your only option to get your bike running again.
Thus, it would be logical to combine the two only in a rare scenario where you don’t have access to chains designed for fewer speeds.
This is unlikely to happen even on a tour because 7/8/9-speed chains are much more common, especially in developing countries, than 11-speed models.
If you have purchased the wrong chain, you can try to return it/exchange it for an 8 or 9-speed model. If that’s not an option, list it online. Be honest in the description. You will be surprised how many people will be interested.
