At root, a bicycle is a simple mechanism. It works by spinning the pedals, which are threaded into crank arms, that are in turn fixed to one or more chain rings. The chain connects the chain ring to the cassette, so when you pedal, the back wheel spins, propelling the bike forward.
Because of its simplicity, a bike’s drivetrain is imperative to it working properly. Your bicycle drivetrain dictates a lot of how your bike is going to ride. As bikes have evolved, especially in the trail and enduro categories, drivetrains have evolved along with them to be simpler and more efficient while offering massive gear ranges. Below we have explained bicycle gearing and its evolution to simpler, more reliable systems.
When a rider shifts gears, it is the derailleur that guides the chain on to a higher or lower gear. Consisting of a spring-loaded cage and two pulleys, a derailleur’s position is dictated by the tension of the metal shift cable, or in some cases, by an electronic signal. So when a rider switches gears on the shifter, the cable pulls the derailleur, which in turn guides the chain on to the next gear.
In the early years, it was common for mountain bikes to have both front and rear derailleurs. This means that there were not only multiple rings comprising the rear cassette, but also two (2x) or three (3x) chainrings on the drive side of the cranks. These gear combinations, referred to as high and low, gave riders multiple combinations of gears to help them get up and down hills.
High gears are made for descending, and consist of a large gear in the front, and a small gear in the back. This ratio provides a high amount of wheel rotation for each revolution of the cranks. It creates more resistance against each pedal stroke, but also allows the bicycle to maintain a high rate of speed.
Low gears are made for climbing, and consist of a small gear in the front and a large gear in the back. This ratio provides a low amount of wheel rotation for each revolution of the cranks. It creates less resistance against each pedal stroke, but doesn’t allow the bicycle to maintain a high rate of speed.
While this system made bikes more capable than they had been in the past, it also had its pitfalls. Having a front and rear derailleur required riders to have shifters on each side of their handlebars, which not only took up space and made bicycle maintenance more cumbersome, but the shifters also confused and distracted riders.
In recent years, a solution to this issue has been found in the 1x drivetrain. Since rear hubs and frames have become wider, engineers realized they could make cassettes capable of carrying the full gear range necessary to get people up and down steep grades, and in doing so, eliminate the need for a front derailleur. This not only simplifies shifting, but streamlines bicycle assembly and maintenance as well.
The 1x drivetrain uses similar high and low gear ratios as its 2x and 3x predecessors, but keeps the front chainring static while allowing all the shifting to occur on the cassette. Because newer cassettes are handling all the shifting, they are required to be larger and have greater gear ranges than older models.
A typical 1x drivetrain may consist of a single 34T or 36T ring in the front, and an 11 or 12-speed cassette with a range of 11-46T or 10-50T rings. For example, a 10-50T cassette has 12 rings which increase in size up to the biggest ring. The smallest ring is comprised of 10 teeth, and the largest has 50 teeth. One way to help visualize this is by thinking of a cassette like a mountain. If you turn a cassette sideways, you’ll notice it’s conical and shaped similarly to a mountain. The low gears at the base of this mountain have the biggest circumference and the most teeth. At the peak, you have the high gears with a small circumference and few teeth. The smaller (high) rings allow riders to pedal at speed, while the larger (low) rings make climbing steep grades much more manageable.
Along with simplifying the drivetrain, the 1x system also frees up space on the handlebar by eliminating the front shifter. This allows riders to mount other components on their bars, like dropper post levers or suspension lockout levers.
Visit our Drivetrain Anatomy page for a full breakdown of drivetrain parts.
If the convenience of a 1x drivetrain appeals to you, there’s a few things you should keep in mind before you run out and buy yourself a new group:
Don’t set yourself up to drop chains. Since 1x drivetrains do not have front derailleurs, they can leave chains vulnerable to falling off the rings. There are two popular techniques to prevent this from happening. The first is by running a narrow-wide chainring. These are specially machined to have alternating narrow and wide teeth, which adhere to the links of a chain to prevent it from popping off the ring. This solution is especially popular for trail, all-mountain, and enduro bikes since it meets the demands of those disciplines. The second technique is to install a chain guide. This solution is better fitting for riders who prefer more demanding, rougher terrain. Chain guides consist of a ring and a backing-plate that sit on either side of the chainring, so the chain can’t bounce off in rough terrain. A chain guide is ideal for downhill and freeride bikes, but requires compatible ISCG (International Standard Chain Guide) mounts to be installed. These mounts consist of a bolt pattern around the bottom bracket made specifically for the mounting of chain guides, and come standard on many long-travel mountain bikes.