1x Drivetrains Explained - Gearing, Mechanics, and Optimization

The simplicity and effectiveness of a 1x (pronounced "one-by") drivetrain, which refers to a single front chainring with multiple sprockets and a rear derailleur, has many people converting their multi-chainring setups. At Wolf Tooth, we were at the forefront of this 1x revolution and want to share a summary of the most important points for 1x gearing, mechanics, and optimization.  

We will cover two main things: 1) why 1x and why now, and 2) What factors should I be aware of to optimize performance of a 1x drivetrain?

Why 1x and Why now?

With only one derailleur to shift, converting to a 1x drivetrain results in simpler, more efficient gearing. You can maintain your gear range and also eliminate gearing overlap and redundancy. Another benefit is the reduced number of parts involved in the drivetrain, reducing the amount of overall weight, as well as the number of components that have to be maintained and replaced.

The increased popularity of 1x drivetrains stems from a confluence of three different technologies:

1. Wide range cassettes
2. Clutch-style rear derailleurs
3. Chainrings that hold the chain on better

Wide Range Cassettes — which are cassettes that have a large range of sizes between the smallest cog and the biggest cog, is the MOST important technology of the three items listed above. 2x and 3x drivetrains have a LOT of gearing overlap, whereas 1x covers nearly the same useful range given the wide range cassettes.

Before there were many options for wide range cassettes for 10- and 11-speed drivetrains, Wolf Tooth was one of the first to offer solutions for cassette expansion with the GC line of cassette extender cogs, where you could swap out the cogs on stock cassettes for a wider range than they originally offered. These products are slowly becoming obsolete as the industry has been embracing 1x setups and offering wide range cassettes more readily.

When you convert to 1x and add a wide range cassette to your drivetrain, your rear derailleur has to be able to handle the larger cogs, so Wolf Tooth designed GoatLinks and RoadLinks to modify stock rear derailleurs with shorter cages to accommodate the larger cogs of the wider range cassettes. 

Clutch Rear Derailleurs — in a few short years, these went from being the exception to the rule. Shimano's Shadow+ and SRAM's Type 2.1/X-Horizon both have a roller clutch controlling the motion of the derailleur cage, which keeps chain movement over bumpy terrain to a minimum. Less chain movement minimizes the chance for the chain to derail from the front chainring.

Chainrings — Without the wide range cassettes and clutch-style rear derailleurs, we probably wouldn't be talking too much about 1x-specific chainrings. But given those two things, it is more exciting to talk about the improvements in the 1x-specific chainrings. A properly designed Wide/Narrow chainring like our Drop-Stop® line of chainrings allows riders to run a chainring with no chain retention device for all but the roughest DH/Enduro racing (small simple chainguides provide that little bit of extra security for DH/Enduro or any situation where you can't afford to drop a chain). Not all wide/narrow chainrings are created equal and we have many customers come to Wolf Tooth after frustrating experiences with cheaper and improperly engineered products.

Our Drop-Stop® chainrings have the most advanced geometry optimizing the chainring life, mud clearing, chain retention and are put through the paces of product testing. We have chainrings to match most 1x drivetrain systems and chains, including the newest 12-speed SRAM AXS Flattop and Shimano Hyperglide+. Additionally, our Chainline And Material Optimization system, or CAMO, allows you to easily swap out front chainrings on direct mount cranks as well as achieve a perfect chainline.

Optimizing 1x Performance

Now that we have covered why 1x is being adopted by so many, let's discuss the key factors that affect 1x drivetrain performance:

1. Chainline
2. Chainwrap
3. Free Chain Length  

To be clear, these same three things affect 2x and 3x performance as well, but because it was much less common to modify 2x and 3x drivetrains, the stock engineered solutions were accepted as optimal. With 1x modifications/upgrades, riders have the ability to mix, match, and customize their drivetrain to their riding style, terrain, and strengths/weakness.

Chainline — The distance in mm between the centerline of the chainring teeth and centerline of the bike. Effective chainline is the center of the front chainring(s) in relation to the center of the rear cassette. Generally speaking, it is best to have the center of the chainring just to the outside of the center of the cassette. However, this is a much longer more detailed discussion when talking exact numbers because of different rear hub spacing (road, road disc, mountain, fat) and tire/chainstay clearance. This is partly covered here for modern mountain bike spacing and here for fat bikes. Chainline affects drivetrain life, which in turn affects long-term shifting.

Chainwrap — this is one of the less-talked-about measurements but is very important to drivetrain life. Chainwrap is the measurement in degrees that a chain engages a cassette. This is most critical when talking about cassette wear, specifically the small cassette cogs. The more chain wrap, the longer the cassette lasts because the load is distributed over more teeth on the given cog.

Free Chain Length — this is very important for shifting precision. Free chain length is the length of chain that extends between the upper jockey wheel of the rear derailleur and the cog on the cassette. The shorter this length of unsupported chain, the more precise the shifting will be. This can simply be explained by the fact that adding more free chain length (links) allows the chain to flex more between the derailleur and cassette so shifting is less precise. Some free chain and flex is needed to allow a shift so there is an optimal free chain length (generally accepted as stock length).

To address Free Chain Length and Chainwrap on modified Shimano drivetrains, Wolf Tooth developed a series of products to optimize 1x conversions. There are many more details on each products page:

1. GoatLink — for Shimano 1x10 conversions with our GC Cassette extenders.  
2. GoatLink 11 — for mixing Shimano shifting with SRAM cassettes (best of both worlds in many riders opinions) 
3. RoadLink — for wide-range cassette use on road bikes
4. RoadLink DM — fits Shimano’s current generation R8000 Ultegra and R9100 Dura-Ace rear derailleurs

In addition to the graphs below, our Gear Charts are useful in understanding what the optimal setup will be for you in your 1x conversion.

Hopefully you now have a better understanding of how 1x works, and the benefits to converting your drivetrain. Our engineers at Wolf Tooth are constantly working to make the best products to improve your cycling experience. Follow us on Facebook and Instagram, or sign up to receive our email newsletter on the bottom of this page to stay informed of our newest products and tech information.