By: Bruce Lin

If you geek out over pro triathlon bikes, or even just look around at all the fancy new bikes showing up at your local races, you may have noticed a growing trend: more athletes are riding bikes with 1x drivetrains. At Quintana Roo, we’ve seen an increase in the number of athletes choosing a 1x setup when they build a new triathlon bike using our custom bike builder, and several of our pro athletes are now full-on 1x converts.

Maybe you’re running into the 1x vs. 2x debate and want to know which side to take. Maybe you’re thinking about buying a new bike or upgrading your drivetrain, and 1x vs. 2x is a serious consideration. So what’s better? One chainring or two? It sounds like a simple question, but there isn’t always a simple answer. Here’s what you need to know.

1x vs. 2x Basics: What’s the Difference?

A 2x drivetrain (pronounced “two-by”) is what most athletes are likely familiar with. It has two chainrings at the front, a big outer chainring and a small inner chainring paired with a front derailleur, which allows you to shift between them. It’s been the standard setup on road and triathlon bikes for decades, and for good reason, it offers a wide range of gears with smaller steps between each gear.

A 1x drivetrain (pronounced “one-by”) uses a single front chainring and no front derailleur. It’s often combined with a wide-range rear cassette. Modern 1x drivetrain technology originated in the world of mountain biking and made its way over to gravel, and in recent years, has started appearing on more road, TT, and triathlon bikes. Compared to 2x, it’s significantly simpler, often lighter, and there are fewer parts to think about.

The Advantages of 2x Drivetrains

The three key advantages of a 2x setup are:

• Smaller gear steps
• Wider gear range
• Straighter chainlines for increased efficiency

For many athletes, smaller jumps between gears are the main benefit of a 2x. Because a 2x has two chainrings, it provides more gear options while also using cassettes with tighter range. This means 2x drivetrains generally offer more 1-tooth jumps between gears. With smaller jumps, it requires less change to your pedaling cadence when you shift. Big cadence changes might not bother some athletes, but if you prefer to fine-tune your cadence to maintain smooth and consistent power output, you’ll likely prefer a 2x. 

2x drivetrains can also offer more overall gear range than 1x setups. With two chainrings, 2x setups often provide both an easier granny gear for climbs and a higher top-end gear for pedaling on flats and descents. This can make your bike more versatile if you’re riding a variety of terrain, from fast and flat to hilly and mountainous courses. 

Finally, keeping your chain straighter increases drivetrain efficiency, and a 2x drivetrain allows you to keep your chain straighter more often. 1x drivetrains tend to have high chain angles at the extremes of the cassette, which increases friction. With a 2x, you can keep the chainline straighter by keeping the chain on the big chainring when using the small cogs of your cassette and the small chainring when using the large cogs of your cassette. Ultimately, the difference is only a few watts, but for marginal gains geeks, that matters. 

The Advantages of 1x Drivetrains

The seven key advantages of a 1x setup are:

• Increased simplicity
• Improved chain retention
• Improved aerodynamics
• Optimized chainring sizes
• Weight savings
• Reduced maintenance
• Cleaner aesthetics

For many athletes, simplicity is likely the number one benefit of going to a 1x drivetrain. With no front derailleur, there are fewer moving parts, fewer things that can go wrong with your bike, and fewer decisions to make when shifting. Reducing mental load with simpler decision-making can actually be beneficial to athletes pushing themselves to the limit. There’s no mental overhead required to think about which chainring you’re in during a race. You just pedal and shift.

The other huge benefit over a 2x system is improved chain retention. If you’ve ever dropped your chain while riding over bumpy roads, it’s a stressful experience that costs you time and energy. Modern 1x systems use narrow-wide chainring tooth profiles and clutch rear derailleurs that keep the chain locked in securely on rough roads. 

Without a front derailleur or second chainring hanging out in the wind, and the added ability to utilize aero chainrings, 1x drivetrains also have a slight aerodynamic advantage over 2x systems. We’ve seen this in the wind tunnel, and so have many of our colleagues and competitors. The gains are small (only a few watts) but measurable. Potentially, the efficiency gains of a 2x providing a straighter chainline could cancel these aero gains out. But that’s where the next benefit comes in.  

When our athletes choose a 1x system, they often select an optimized chainring size for a specific course. For example, our top male pro Kristian Høgenhaug picks a massive 58t 1x chainring for flat courses. Larger chainrings are generally more efficeint than smaller chainrings, and Kristian is able to maintain a straighter chainline for the majority of the race, maximizing his drivetrain efficiency. His setup isn’t great for climbing, and different courses might require swapping to a different-sized chainring, so it isn’t as versatile, but it lets him dial in his gearing to maximize gains on a specific type of course.

Then, there’s some weight savings. Ditching a chainring, front derailleur, and the associated cables saves a bit of weight, around 150–300 grams depending on the system. If you’re a weight-weenie or tackling a hilly course, that could be a meaningful gain.

Finally, 1x’s offer reduced maintenance and (in my opinion) cleaner aesthetics. Fewer components mean there’s less to go wrong, less to maintain, and less to clean. Many athletes also just prefer the clean and modern look of a single chainring setup on a modern tri bike. 

1x vs. 2x: How to Choose

IF you’re on the fence about choosing a 1x or 2x drivetrain, there are three key questions to ask yourself:

What does your target race course look like? Is it flat and fast? A 1x will shine here. Is it rolling or mountainous? A 2x will give you more range and finer control over your cadence. That said, 2x will work well on a flat and fast course too, and a 1x will work in the mountains as long as you are using the right chainring size for your power and fitness. 

How much do you value versatility vs. optimization? For me, this is the more important question. Are you always riding on flatter terrain? Go ahead and get a 1x. Are you dialing in your drivetrain for one very specific race (e.g., Kona)? A 1x gives you that laser focused optimization. But are you trying to ride anything and anywhere? Do you want to tackle any race without futzing with your bike? A 2x might be a better option because you’ll worry less about running out of gears or having the right size chainring for the terrain. 

What shifting experience will you prefer? This final question is where personal preference comes into play. I chose a 1x because I like the experience of riding a 1x. I like just going up and down the cassette and not having to think about shifting a front derailleur. I like that my bike looks and feels simpler. But this might drive other athletes crazy. Maybe you prefer the feel of small steps between gears and the ability to drop into the small chainring when you hit steep terrain. If so, stick with 2x. 

1x vs. 2x: The Bottom Line

Both 1x and 2x drivetrains are excellent choices for triathlon, and the best one is simply the one that matches how you ride and race. If simplicity and performance optimization is your priority, and versatility isn’t a concern, I vote for a 1x system. But if you need your bike to perform anywhere, or you just prefer the small gear steps and feel of a classic 2x system, there’s nothing wrong with that! Even though 1x drivetrains have grown rapidly in popularity, 2x isn’t going anywhere. We see athletes succeed using both, and ultimately, it’s the athletes who make the biggest difference in performance.