Condensed Answer: Narrow-wide chainrings are fairly thin since they’re designed for multi-speed chains. Meanwhile, single-speed chains are wider than multi-speed chains and the narrow-wide ring will have no problem fitting between the plates.
Thus, a single-speed chain can operate with a narrow-wide chainring.
That said, the combo makes little practical sense unless you already have the parts.
What is the purpose of narrow-wide chainrings?
The purpose of narrow-wide chainrings is to increase chain retention on multi-speed drivetrains that don’t use a front derailleur or a dedicated chain guard.
Narrow-wide chainrings have teeth of alternating width – one is narrow, the next is wide.
This pattern is specifically chosen to match the varying width of a chain.
A chain has inner width formed by the inner plates and outer width formed by the outer plates – img. below.
The wide teeth slide between the outer plates whereas the narrow ones go between the inner plates. As a result, the chain is less likely to drop on a system without a front derailleur or a chain guide.
Since narrow-wide chainrings are designed for 1x set-ups, the wide teeth on a narrow-wide chainring cannot be wider than the outer width of the chain.
Most narrow-wide chainrings are engineered for 9,10,11 and 12-speed chains.
Thus, the wide teeth of the chainring cannot exceed the outer width of a 12-speed chain which is the narrowest on the list.
As gears increase, the outer width of the chain diminishes too. Otherwise, the chain would start rubbing against the adjacent cogs.
Contrary to what a beginner might believe, the overall width of a cassette does not increase dramatically with each gear jump. It just gets denser. The goal is to make the cassette compatible with multiple hubs.
Single-speed Chain Width
A 12-speed chain has a 5.3mm outer width and a 2.18mm inner width. A narrow-wide chainring reflects that.
Meanwhile, a dedicated single-speed chain has a 1/8″ (3.3mm) inner width and about 9mm outer width.
Single-speed chainrings are therefore thicker to fill up the extra space. Consequently, single-speed chains cannot be used with ultra-narrow multi-speed cassettes. The chain will just get stuck.
However, this isn’t the case for narrow-wide chainrings because they’re slimmer and thus compatible with a single-speed chain.
Note: There are also 3/32″ (2.38mm) single-speed chains. They are narrower than the standard 1/8″ models but still sufficiently wide for any narrow-wide chainring.
The Benefits of Combining a Narrow Wide Chainring with a Single Speed Chain
A single-speed chain is very wide and lacks lateral flexibility due to the bushings connecting the inner plates. As a result, it cannot be used with a derailleur system.
Thus, a single-speed chain is compatible only with single-speed bikes and models with internal gears.
Those types of bikes do not have a problem with chain retention because the chain doesn’t move laterally to shift. Thus, the chain retention offered by a narrow-wide chainring is meaningless in this case.
Ultimately, the only benefit of this combo is the recycling of available parts. If you’re looking for a new chainring to use with a single-speed bike, purchase a dedicated single-speed model because it’s thicker and will last longer than a narrow-wide one.
The Downsides of Combining a Single-speed Chain with a Narrow-wide Chainring
The combination has two theoretical downsides:
- A sloppy connection between the chainring and the chain due to the width discrepancy.
- Faster wear of the chainring and cogs.
In practice, however, people have been reporting no perceivable problems with the combination. Thus, it is questionable to what extent the above issues manifest.