Does 1x Shifting Reign Supreme?

Today I want to talk about the evolution of the 1x drive train, especially as it relates to the sport of triathlon. Personally, I’ve been a huge fan of the idea for a long time, back when it was considered the “obviously wrong” choice in our sport. And to be fair, the arguments against it were stronger at the time. But as our sport has evolved and developed, both the acceptance of 1x drivetrains in triathlon as well as the equipment to enable and support them have vastly improved. So let’s talk about what they are, how they’ve evolved, and why now is an incredible time to get rid of that second chainring.

So, backing up, what is a 1x drivetrain? Does it require a clutch? Is it for 10t cassettes only? You might be confused with certain modern terminology and technology that has come up in the past few years, but the actual definition of a 1x drivetrain is simply any bicycle setup which lacks a front derailleur and relies solely on the rear derailleur to shift through the gears. For the sake of completeness, I’ll just mention that if you don’t have a rear derailleur either, that’s no longer a 1x setup. That would be either a single-speed bicycle (if it has a freewheel allowing you to coast), or a fixed-gear bicycle (if there’s no freewheel, and the movement of the rear wheel is always connected to the movement of the crankset). A 1x drivetrain always has a cassette with some number of gears, a rear derailleur to move through them, and a single front chainring. The name comes from the combination of gears, determined by that rear cassette. If your cassette has 12 cogs, you’ve got a 1x12 drivetrain. If it has 13 cogs, that’s a 1x13 setup. And so on.

Back when I built my first 1x drivetrain, it had a paltry 11 gears in back. The range was somewhat limited, I believe it was an 11-27 cluster, mated to a 44-tooth front chainring. Its drivetrain components were all adapted from a 2x setup, with the exception of the custom-built chainring from Fibre-Lyte. It didn’t have any of today’s fancy technology in terms of a derailleur fluid clutch, or narrow-wide tooth profiles, or variable-angle chainlines. Yet it was still more than enough for everything I needed it to do, and was a fantastic bike to ride. This thing weighed in at all of 11 lbs, and is still one of my favorite builds to this day.

But what did I give up to achieve that build using the technology of the day? Not much, but some significant things. First, let’s look at our gear range. The hardest gear on this bike is a 44-11, which is easily going to spin out on a significant descent. Not a huge deal, but no one is going to win Kona with that gear ratio, especially coming down from Hawi. Next, the clibming gear still leads a bit to be desired – 44-27 is still a lot of gear to push when you’re climbing in the foothills of Colorado.

Moreover, using a regular 2x drivetrain meant that there was going to be a bit of chain slap and the occasional dropped chain, especially at the extreme ends of the gear range. And at those extreme ends, the chainline is not quite straight, meaning you introduce some friction losses which sap a little bit of your power.

Overall this build was a nice balance of the options available at the time, and the best compromise given what existed.

Today there are better options, and you can not only reduce those compromises, but virtually eliminate them. If granularity of gearing is most important, but you still want a really strong descending gear, SRAM offers cassettes with a 10-tooth cog, which makes a big difference. If granularity is less important, but you still want a lot of range, you could use a larger ring up front, with a cluster as wide as 10-42 in back, because we now have both the cassettes and the derailleurs to accommodate that wide a range. But going that route, you’ll be missing a LOT of steps in between those gears that might be exactly where you want to live a lot of the time.

Right here is a build we recently did on a Cervelo P-Series frame. It has very race-oriented but still middle-of-the-road gearing options. It’s a 50-tooth chainring, with 12 gears in back ranging from 10-32 teeth. This rig has a much stronger descending gear than the earlier rig I showed you, about the same climbing gear, and doesn’t miss much in the middle due to having more gears total.

In addition, SRAM’s modern 1x derailleurs and chainrings do a lot to improve the 1x experience.  The narrow-wide tooth profile and fluid clutch in back really do reduce and virtually eliminate chainslap and chain drops, meaning you can just focus on the ride. The derailleur geometry also pivots slightly as you go through the gear range, reducing drivetrain friction losses.

All-in-all, modern 1x setups – and by that I really mean SRAM’s products – really do eliminate what used to be a bit of hassle or compromise in 1x drivetrains. You get to remove that front derailleur which has its own potential weight and aerodynamic savings, but you also get to forget about its existence. As you ride, all you have to think about is whether you want the gear to be “harder” or “easier” and click the appropriate button.

But … let’s not count out the front derailleur entirely. Shimano, for their part, has really doubled down on the double chainring. Their latest Di2 systems for triathlon all, by default, operate in that same “harder” or “easier” mode that I just described, but they do it even with that front derailleur present. They just shift that front derailleur automatically depending on what gear you’re in and which direction you’re shifting. This is a pretty solid answer to the increased interest in 1x drivetrains. With Shimano’s Synchronized Shifting in place, you get the same “no brainer” benefit from 1x, but with the benefits of a true 2x system; the improved chain retention, lower drivetrain friction, more granular gears, and a wider total gear range.

Personally, I still fall on the side of the 1x camp. I fell in love with the concept way before it was cool, and I’m not giving up on it just because now it IS cool. I’m a total sucker for simplicity, and elegance, and modern 1x bikes are just too beautiful not to love.