The state of narrow/wide chainrings
How bicycle chainrings evolved to what we know today as narrow/wide chainring
SO NARROW/WIDE THEN?
Nowadays there are a lot of companies that offer chainrings with alternating tooth profile. You can pick a component perfectly matching your taste: of any color and shape. Some manufacturers put the engraving on their products, which is great yet it does not improve the performance.
So how different models really differ from each other? What should you pay attention to while choosing a narrow/wide chainring?
If we will look at these questions from the technical point of view, we should admit that there are certain fundamental differences between the regular chainrings and those designed for 1x drivetrains, for example:
modified shape of a tooth profile;
Each of the elements mentioned above affects the chain retantion in a big way.
ALTERNATING TOOTH WIDTH
At this point, we should probably dip a little deeper to make everything seem more obvious.
If you will look closer at the links composing bike chain, you can see that they have different width. Standard chainrings have teeth of a similar width to accomodate chain at its narrow link, but at the same time an extra gap appears between the chainring teeth and wide chain link.
This gap will make it easier for the chain to drop during bike shaking and vibrations caused by bike movement. Chainring with alternating tooth width minimizes the gaps between chainring teeth and wide chain links to ensure the best possible chain retention.
When replacing your standard crankset chainring with the one designed specifically for 1x drivetrains, you want to be sure such ring will work seamlessly without any additional bike equipment (chain guides, etc.). Most of the standard chainrings (GOST, ISO, DIN-standardized) fail miserably at providing good chain retention in various conditions, because they were designed to be as universal as possible. Making a "universal" solution in this case will almost certainly require extra tolerances, which will result in the above mentioned gap between the chain and chainring teeth. We think that making a "univeral" solution is not our case.
An idea we had in mind when desiging our chainrings was to make a product that will take quality of chain retention to a whole new level. However, when you need to design such a solution, you face a few problems. First, you cannot just design a chainring teeth that allow maximum retention for the chain, because, when the chain stretches (it will, eventually), such design will turn from a feature to flaw.
Various manufacturers came up with ideas that encompass their own experience and knowledge while designing a solution for such problem. Picture below demonstrates the non-efficient way to design a chain retention tooth profile ("A") and a proper one ("B"). It's doesn't take much time to understand that solution "B" will offer greater chain retention while variant "A" does almost nothing to prevent chain dropping due to its sleeker design.
It's sad that some well-known companies implemented almost standard teeth design for their latest chainrings and there are certain doubts about their quality when it comes to chain retention.
Another example demonstrates a cleverly designed tooth profile and yet the height of the teeth is unchanged.
We think that height of the chainring teeth is one of the most important features that distinguishes a proper 1x chainring from a poorly-designed one. During chainring rotation, its teeth should be inserted correctly into the chain links and at the same time quench the transverse chain oscillations. In reality only few chainring teeth are important during this engagement, as pictured below (with 30T chainring).
As you can see from the picture, chainring with high teeth (on the right) prevents the transverse chain oscillations with three of its teeth: tooth marked #1 is fully inserted into the chain link, #2 holds the chain securely enough to not let it drop. #3 has just begun to engage yet it holds the chain already.
Regular chainring (on the left) holds the chain only with two of its teeth. While the first tooth is fully engaged, the second one only partially holds the chain (and can easily drop the chain during heavy bike jolt). The third tooth of the regular chainring only approaches the chain link, without holding it, so the reliability of such solution is at least 30% worse.
Certain manufacturers ventured to abandon the alternating teeth width design in favor of standard teeth with increased height. For example, Shimano and FSA use high teeth with non-alternating teeth width on their 1x drivetrains. During our own testing of such solution we were able to figure out that it works quite well. Still there are more tests to come and it's early to draw a line here right now. Probably, this could become a subject for our next article.
Diagram below illustrates our comparison of teeth height implemented by various manufacturers in their chainrings (accuracy is within ±1mm).
Some of the riders who used narrow/wide chainrings could notice that they get muddy much easier than non-narrow/wide ones. This is due to the fact that narrow/wide chainring removes the gaps between the chain links and chainring teeth, which works perfectly when the drivetrain is clean, but with mud adhesion the efficiency of such solution rapidly fades away. In this case a compromise is highly required.
SRAM is a company who got furthest while trying to solve this problem. Or did they?
On their chainring prototypes there is a special cut out which prevents mud from adhering and accumulation (shown on the picture below).
As it turned out, this "innovaton" is not that new. SRAM simply implemented a solution well-known and widely used in motocross. Moreover, while applying such mud removal method on their production samples, SRAM simplified the design of mud gap for some models, presumably for keeping the costs down a little bit.
Our own testing showed that an effective mud removal solution requires applying a wide mud gap. On the picture below, a classic narrow/wide chainring recession is displayed (A). Because the recession is equidistant from teeth's outline, an accumulated mud doesn't get cleaned efficiently, which leads to chain drops as a result of a poor chain retention.
Picture below demonstrates how the mud can be cleaned properly. With proper recession, there is more clearance and mud doesn't get stuck in the engagement zone, which results in a significantly more efficient chain retention.
While designing our chainrings, we went through many iterations of testing, modified and seriously improved the chain retention quality for the products we delivered to the market and shared with our happy customers.