Consider the drivetrain: Arguably the most important part of a bicycle, the drivetrain has seen countless configurations and standards come and go and come back again. From single speed all the way up to 13-speed, it seems that each new iteration of a bicycle’s drivetrain just keeps adding new gears to make climbs easier and descents faster. Why, then, are so many riders these days ditching their front derailleurs and switching to a 1x setup?
What the Heck Is a “One-By”?
A one-by—or 1x—drivetrain refers to a setup with a single chainring up front and any number of gears on the cassette. The most commonly seen today are 1x10, 1x11 and 1x12. The concept of 1x drivetrains is nothing new. For many years, if riders wanted a drivetrain that was simpler than a 2x or 3x, yet more versatile than a single speed, they had to resort to cobbled together solutions with lackluster reliability. Chains would drop, gears would mis-shift, and the ideal gear range simply wasn’t there. Luckily, with the advent of three key technological innovations, 1x drivetrains are now more attainable and easier to set up than before.
Why Go 1x?
While there are a number of benefits that 1x drivetrains offer, the best answer to “Why 1x?” is simplicity — both in terms of maintenance and usability. Front shifting is more difficult to set up and maintain, and is the least mechanically robust part of any drivetrain. By removing it from the equation, the drivetrain becomes more simple and effective. In addition, it’s not uncommon for less experienced riders to misuse their front derailleur and find themselves cross chaining. This can cause issues down the road, as cross chaining puts extra wear and tear on a chain, requiring it be replaced more often than it would otherwise need to be. Again, removing that front shifting variable allows the rider to focus on only the rear derailleur and eliminates any fear of cross chaining. Lastly, for riders who like to watch their weight, switching to a 1x is ultimately going to be lighter than any 2x or 3x drivetrain. Although a clutch rear derailleur is slightly heavier than a standard rear derailleur, removing the front shifter, front derailleur, and a chainring or two sheds upwards of 200g from the weight of the bike!
How Does 1x Work?
As long as the following three things are present, a 1x drivetrain will provide the rider premium and precise shifting performance.
One of the biggest issues facing DIY 1x setups of the past was dropped chains. Caused by a buildup of mud or debris on the chainring, dropped chains were once a regular occurrence while shifting, sprinting, or taking sharp turns. Enter the wide/narrow tooth profile. These specifically designed chainrings mirror a chain’s inner and outer links and guide the bouncing chain to mesh with the chainring’s teeth as it falls into position. This provides a secure fit and maximum control. While this technology on bicycles dates back to the 1970s, it really wasn’t until it was combined with clutch rear derailleurs and wide-range cassettes that it was deemed a viable option for 1x setups. Several different brands utilize wide/narrow, like SRAM’s X-Sync2™, Wolf Tooth’s Drop-Stop™, e*thirteen’s M Profile, and Race Face’s Narrow/Wide series to name a few. Each brand has slight variations in the design and engineering of how the technology is utilized in its rings, but the same three things are considered: wear, mud and debris clearing, and the chain retention on the ring.
Ten years ago, the average mountain bike cassette had a 9-speed range of 11–32t. With the birth of modern 1x drivetrains—along with SRAM’s XD driver body—that range has been expanded greatly, cassettes are now commonly available with 9- and 10-tooth high cogs and low cogs in the 40 and 50s. This range provides most riders with all they need on the trail. The wide gear ranges have virtually eliminated the need for multiple chainrings up front, as nearly the same gearing can be achieved by going 1x.
Clutch Rear Derailleur
The final piece of the puzzle when it comes to a successful 1x setup is a clutch rear derailleur, which utilizes a roller clutch to minimize the chain’s movement as the bike bounces around on rougher terrain. While initially expensive and only available at the top end, this technology has trickled down to lower price point groups making it much more affordable. Both SRAM and Shimano offer clutch rear derailleurs, meaning you can experience virtually no chain slap regardless of which brand you prefer. In fact, clutch technology has proven so beneficial to performance on the mountain bike side of things that SRAM and Shimano utilize it in its road and cyclocross drivetrains as well.
For many people, switching to a 1x drivetrain seems like a fairly daunting, not to mention expensive, task. It’s a common misconception that when it comes to 1x, it’s all or nothing—you either have to buy a full group or keep shifting with a front derailleur. Fortunately, that’s not the case at all. While there are a growing number of complete and inexpensive 1x groups on the market that work extremely well, other brands—like Wolf Tooth and Race Face—have products available that convert a rider’s current setup to 1x. For example, say a rider comes in with a 2x10 setup. They’ve been hearing a lot about 1x and are hoping to test the waters without a lot of investment before going to a full 1x12. By recommending a Wolf Tooth Drop-Stop™ 32t chainring, and SRAM GX or Deore M6000 clutch-type rear derailleur, you can help them dip their toe in to 1x without replacing the entire drivetrain. Additionally, if they’re looking to extend their gear range to more closely match an out-of-the-box option, the Sun Race 11–42 cassette is a cost-effective option to do just that.
If and when they decide they want to go full 1x12, there are a growing number of affordable groups available. With SRAM being 1x pioneers of sorts, the technology extends to a most of its groupsets — from entry level to high end. In addition to 1x11, SRAM upped the ante with the release of its Eagle 1x12 groups. At first only available in XX1 and XO1 options, it has since trickled down to NX. Eagle offers massive 10–50 cassettes on an XD Driver or 11-50 cassettes on an HG driver for a whopping 454–500% gear range.
With the number of 1x-specific components on the market, it’s pretty clear that 1x is here to stay. In fact, the 1x trend has made the jump from mountain bikes to cyclocross bikes and now, most recently, to road bikes. As more and more subsets of cycling embracing the 1x drivetrain, it has become clear that front derailleurs are essentially dead in the mountain bike world. Only time will tell if this small, yet complicated component will weather the 1x storm in road, gravel and cyclocross.