It's a debate that never seems to end, and anyone contemplating buying or building their next gravel bike has probably spent at least some time weighing up their options.
But before we get stuck into the meat of the debate, and try to decipher which of the best gravel bikes will work for your needs, first it makes sense to start with a basic understanding of the discussion. Those of us deeply immersed in bike technology can sometimes take for granted that everyone understands the ins and outs. Not everyone does and so, let's start with what are we even talking about here? What does the term 1x (one-by) and 2x (two-by) refer to on a bike?
The signifiers, 1x and 2x, refer to the front chainrings. With a 2x, or 3x which does also exist, there multiple front chainrings, which multiply the number of gears available on the rear cassette. That means if you've got a 2x system, for example, then there are two chainrings up front and another piece to the sentence. To finish the sentence, you'd say "two by twelve", or however many gears the cassette has, and you'd be referring to a bike with twenty-four total gears in the case of 2x12. If it's a 1x system then there's only a single chainring up front and all your gearing steps come from what's available on the cassette.
In order to have two chainrings up front, you also need a front derailleur. The front derailleur doesn't often get mentioned in these discussions but it's a significant part of the debate, because it's impossible to have two chainrings without a way to switch between them, and that has implications for the design of a bike as well as how it's ridden.
Why do bikes traditionally use a 2x design?
Pure and simple, the advantage of a 2x design is that you get more gears. It might seem obvious that more gears are better than less, but it's not really the number of gears that matter. What's more important is the spacing between the gears.
Road bike gearing was developed for racing, and that matters because it keeps the desired speed and cadence in a somewhat narrow range, making for smoother shifting, and preventing that jolt you feel when your chain shifts across a large gap. The bikes are light, the speeds are high, and efficiency is the most important thing. You need a lot of gears spaced as closely together as possible, so that you can keep your cadence feeling just right as the pack makes small adjustments in speeds.
Keep following that same thread and you can see how 2x solves the problem. There's an upper limit to the number of gear ratios available on a cassette. You could space those gears out a lot but the jumps would feel unsettling and it would be tough to find an optimal gear. If you want enough range to climb a hill, the best way to add it is with a second chainring. It allows a bike to have small steps between gears but also a second, easier, set of ratios for climbing.
What fueled the shift to a 1x design?
That description of 2x makes it sound technically superior and it brings up the obvious question of why even consider 1x? The answer to that one isn't as simple as why 2x makes sense. Getting to the bottom of it all starts with gravel cycling and the unique design challenges it brings with it. It's also a story about the continued development of cycling technology.
We talked about this a bit in our discussion of the best gravel suspension forks, but the bottom line is that there's no easier way to make a more capable gravel bike than to increase tyre size. As you start making tyres wider though, you run into packaging issues. You need room for the front derailleur, the tyre, the chainrings, and the crank arms all in about the same spot. Mountain bikes solve the challenges by having a wider crank and a longer bike, but gravel bikes are more compact, like road bikes. The groupsets used are based on road bike groupsets, and the desired geometry is pretty close to a road bike as well.
Early gravel bikes adopted a variety of tricks to solve this problem. Cannondale used an asymmetric rear end called AI that shifts the hub of the rear wheel towards the drive side. Most metal bike frames, like the Litespeed Watia frame, just flatten out the drive side chainstay for a short distance. For carbon bikes, Gerard Vrooman came up with the revolutionary solution of dropping the chainstay on the Open UP bike and it's been widely copied since it came out.
There is another solution though, and it's a lot less complicated. Instead of solving the problem, just eliminate it and use only a single chainring. The chainring will be smaller, to have usable gearing, and there's no front derailleur to consider, so packaging issues disappear. Not only that, but without the need to move the chain smoothly between chainrings, the tooth design can focus on keeping the chain from falling off. You end up with a bike that's lighter because there are fewer pieces, a more secure chain over big bumps, and a bike that's nice and short for a spirited feeling. It's an elegant solution but it only works because of what gravel cycling was.
In the beginning, the focus of gravel cycling was exploration and adventure. Gravel racing wasn't in the place it is today and the needs of early gravel riders didn't include keeping cadence in an optimal range while riding at speed in a pack. It was no big deal to have larger jumps between gears as long as the range was sufficient.
What are the current design trends in gravel cycling?
Gravel cycling has changed a lot since the early days. More and more people are riding gravel bikes and the increased popularity has brought increased competition. Gravel racing has moved from a small part of a small market to a major force in the use and marketing of gravel bikes. There's also been significant advances in the gearing choices available and that's a factor in the options you have available and the choices you might want to make.
In those early days of exploration there were road race bikes and there were gravel bikes for exploring. Now the market has fractured into adventure gravel bikes and gravel race bikes. Gravel race bikes have moved closer and closer to road bikes and in that transition, they've picked up a lot of the same design features. For the purposes of our discussion, what that means is that gravel race bikes almost always have 2x gearing. There's also been a rise in the blended all-road category of bikes and those tend to be 2x as well.
At the same time, adventure cycling hasn't disappeared. There are still plenty of people who don't mind having larger jumps in gears. Coasting down a descent isn’t an issue for this group and the advantages of packaging that 1x gearing brings haven't changed. There's still less complexity in a 1x system and that appeals to those who are heading far off-grid. Along the way there’s also been further introduction of gearing that’s in between a mountain bike and a road bike. Smaller front chainrings paired with bigger cassettes have opened up the choices that are available to both sides of the gravel cycling spectrum.
Should you choose 1x or 2x for your next gravel bike?
As you look through our list of the best gravel bikes, you'll need to make the choice for yourself. The way bikes are being designed and marketed is one thing, but it doesn't capture everything you should consider. If you are looking for a bike to do double duty at the pointy end of gravel races as well as road riding, then you are going to want a 2x system. The extra gear choices will mean that you can keep an optimal cadence in a group and you'll also have the range to climb. That's a pretty straightforward choice for the most competitive riders.
For those who are more interested in exploring the roughest routes, then 1x is where you'll want to look. One of the biggest advantages, which we haven't already touched on, is the simplicity of riding a 1x groupset. There are fewer components to fail and that's an advantage for backcountry riding but there's also a simplicity to shifting. Anytime you are riding a 2x groupset you'll want to avoid cross-chaining (using both big rings or both small rings at the same time) and you'll want to consider when you upset the chassis of the bike with the large jump that comes from shifting the front chainrings. It's easy to make those choices on relatively smooth terrain. Things change off-road, though. When you are climbing a steep and rocky trail, there is a lot going on. You’ve got to balance your weight between the front and rear to keep traction and look for the best line. Your concentration is on riding, not thinking about what gear you are in and it's much nicer to have a simple 'easier or harder' shifting decision.
Riding 1x on a gravel bike has a lot of advantages but it also brings drawbacks. You'll either need to sacrifice range or you'll need to deal with large jumps between gears. Things are changing fast though. SRAM XPLR, Campagnolo Ekar, and Rotor groupsets change the equation with options for 1x12 and 1x13. There's even the option to go with gearing in the rear hub by adding the Classified system to your next bike. It's possible now to get incredible range without sacrificing tight spacing, but there is still a cost disadvantage. If you've got the available budget, you might find you can get all the advantages of both 1x and 2x on the same bike.
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Josh hails from the Pacific Northwest of the United States but would prefer riding through the desert than the rain. He will happily talk for hours about the minutia of cycling tech but also has an understanding that most people just want things to work. He is a road cyclist at heart and doesn't care much if those roads are paved, dirt, or digital. Although he rarely races, if you ask him to ride from sunrise to sunset the answer will be yes.
Weight: 137 lb.
Rides: Orbea Orca Aero, Cannondale Topstone Lefty, Cannondale CAAD9, Trek Checkpoint, Priority Continuum Onyx