An Introduction To 1x Drivetrains

Back in 2012, Sram revolutionized mountain bike gearing with the announcement of their XX1 groupset, the first mass-produced 1×11 (pronounced “one by eleven,” meaning one chainring up front and eleven cogs in the back) system for mountain bikes. Out went the front derailleur, and in came the ultra-wide range and massive rear cassette.

They didn’t invent 1x (pronounced “one by”) drivetrain, as many mountain bikers were doing home conversions to 1×10 with chain catchers already, but they were the first to mass-market it as a system.

At the time, most mountain bikes were 2×10, which means you have two chainrings up front and ten cogs on your cassette in the back, and other mountain bikes were 3×10, or even 3×9 and 3×8 depending on the price point. For some, ditching the front derailleur was a great idea, but for others, the loss of maximum range of gearing wasn’t worth it.

How Does 1x Work?

Typical 1x drivetrain requires two components: a “narrow/wide” chainring and a rear derailleur with a clutch mechanism.

The narrow/wide chainrings, which go by a number of trademarked names depending on the brand, have teeth with alternating fat and skinny profiles to make a tight fit inside the chain, thus helping chain retention.

The clutch derailleur, meanwhile, allows the derailleur to move when shifting but otherwise stays in place, which eliminates “chain slap” – the chain slackening and slapping against the frame in bumpy terrain – almost completely.

The combination of these two things means that you can run your drivetrain without a front derailleur or even a chain catcher without worrying about the chain “dropping,” or coming off the chainring.

narrow wide - An Introduction To 1x Drivetrains

Who is 1x for?

The first 1x systems were originally targeted at elite racers who wanted to eliminate the chance for dropped chains during front shifting and to reduce weight.

It didn’t take long for the technology to trickle down to more affordable price points, though, and now you can find 1x gearing on entry-level bikes where simplified shifting is a huge selling point.

Instead of having to worry about the correct gear combinations and shifting both front and rear derailleurs together, your shifting is simply sequential with only the rear derailleur to worry about.

Gone are the worries about things like cross chaining, where your chain runs at extreme angles, increasing wear on your components

cross chain


Is 1x gearing for everyone?

As a general concept, 1x gearing can function for nearly any type of cycling you can imagine, from triathlon bikes to downhill mountain bikes, and short trip commuter bikes to multi-day touring bikes.

With a limit on the number of rear cassette cogs, though, the realistic gearing range or the gaps between gears can make a 1x system less than ideal.

Component companies both small and large are trying to address some of these issues with things like wider range cassettes (with large cogs having as much as 50 teeth or more!), aftermarket cogs to add to existing cassettes, and even 12 speed systems! Even still, it’s not necessarily for everyone, especially when it comes to road riding.

For example, on a mountain bike ridden primarily on off-road trails, the common 11-42 cassette (the smallest cog has 11 teeth and the largest has 42 teeth) gives a wonderful range for terrain that changes grade sharply and is rarely flat for long periods of time.

The range gives you small cogs (high gears) for fast speeds on long fire roads or big downhill sections, and large cogs (low gears) for incredibly steep uphill climbs or technical terrain, with fairly smooth transitions in between.

With increases in cassette sizes and even more so with the addition of a 12th cog on newer groupsets, you effectively get the same range as older 2×10 systems but without having to worry about a front derailleur.

mtb cassette - An Introduction To 1x Drivetrains

As great as this is on trails, a wide range cassette can feel terrible on the road. On a road bike, a smaller range like an 11-28 or 11-32 cassette (with the largest cog having only 28 or 32 teeth, respectively) leaves small gaps between gears for steady pedaling cadence, which is more appropriate for the gradual change in grade on most paved roads and smoother shifting overall.

It comes at a price, though. Since road bikes need chainrings that are much larger than mountain bike chainrings you may not have low enough gears for climbing mountain roads, or may have a high enough gear for fast speeds but still have too wide of a gap between gears for smooth pedaling on relatively flat terrain. These are major contributors to why 1x technology has been slow to catch on for road cyclists.

road cassette -- An Introduction To 1x Drivetrains

Can 1x work for you?

In my personal experience, 1x technology has been a great addition to the cycling world, and for most situations, it can benefit your riding by simplifying shifting and maintenance.

I can’t imagine ever going back to a 2x system on a mountain bike, as the easier shifting and complete lack of dropped chains from bad front shifts has helped me enjoy mountain biking so much more.

For road riding, though, it really depends on what I’m going to be doing. I have a commuter bike that gets ridden locally, where we have lots of rolling hills but nothing too strenuous, and an 11-32 cassette paired with a 40t front chainring work perfectly.

However, I’d never take this on a very long ride outside of my local area, especially to the mountains, where I’d much prefer the wider range of a 2x setup using 34t and 50t front chainrings that gives me a huge range while using a cassette with tight gaps between cogs, in this case, 12-30.


Technology is changing quickly, and many cyclists are finding that 1x gearing is perfect for them. At a time when electronic shifting is standard on high-end bikes and 1×12 gearing is starting to become the mountain biking norm, I would not be surprised if nearly all bikes we buy in the coming years are using 1x drivetrains, and any technology that makes cycling more accessible and enjoyable is technology we should embrace.

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