An 8-speed chain is usable with a narrow-wide chainring, but the combination isn’t ideal because 8-speed chains are wider both internally and externally than 9/10/11/12-speed models.
And since most narrow-wide chainrings are optimized for 9/10/11/12-speed chains, the connection better the chain, and the ring’s teeth won’t be as tight as needed for optimal chain retention and power transfer.
Therefore, it is recommended to use this combination only when you don’t have access to a thinner chain or an 8-speed narrow-wide chainring.
Chain Width Is Crucial
The deciding factors for chain and chainring compatibility are:
- Chain width
- Chainring teeth thickness
- Gearing
Bicycle chains have inner and outer widths.
The inner width is the distance between the inner plates; the outer width is the distance between the external plates.
Narrow-wide chainrings have one main goal – to improve chain retention on 1x drivetrains.
1x drivetrains (drivetrains with a single chainring) have no front derailleurs and face a greater chance of a dropped chain due to poor chain retention.
In the past, this problem was remedied via chain guides, but narrow-wide chainrings made those obsolete in many situations.
How does a narrow-wide chairing work?
Narrow-wide chainrings have teeth of alternating width. One is wide; the next is narrow.
The narrow tooth goes between the inner plates of the chain; the wider tooth slides between the outer plates.
Thanks to the alternating tooth widths, the chain wraps tightly around the chainring. The result is supreme chain retention and lower chances of a dropped chain.
In different, standard chainrings have teeth of identical width. As a result, there are larger side gaps between the teeth and the outer plates. The extra spacing makes the chain more flexible and helps with shifting but hurts chain retention when operating in 1x mode.
Most narrow-wide chainrings are optimized for 9/10/11/12-speed chains. In other words, the thickness of the teeth respects the outer and inner width of those chains. If the teeth are too thick, they will bind; if they’re too narrow, they won’t provide the needed chain security.
The inner and outer width of 8-speed chains is different, however.
Why?
Chain width depends on the number of gears on the cassette. As the number of gears increases, chains get thinner because the cogs on the cassette get closer to one another.
This “density” is needed so that the same hub can accept a multitude of cassettes. Hence the possibility of installing a 10-speed cassette on an 8-speed hub, for example.
That said, the inner width of 9/10/11/12-speed chains is the same because the thickness of the sprockets doesn’t change.
7 and 8-speed chains, however, have a larger inner width.
The table below contains the inner and outer widths of most 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 |
8-speed chains have a 2.38mm inner width and a 7.3mm outer width. Those dimensions are respectively 0.2mm and 1.3mm larger than what we see on chains designed for fewer speeds.
The inner width discrepancy isn’t massive, but the outer width difference is fairly substantial and will hurt the chain retention properties of standard narrow-wide chainrings due to the extra space between the ring’s teeth and the outer plates.
The system would still be usable, just not ideal. To minimize the chances of a fallen chain, it may be necessary to use a chain guard.
Another option is to get a narrow-wide chainring made specifically for an 8-speed chain. The company BOX makes one (read more).
