A few years ago, the single chainring burst onto the mountain bike market with great force, initially leaving as many supporters as detractors. At first, this new transmission system seemed more like a step backward than an advancement in product development by SRAM and Shimano. The older riders among us remember that crazy neighbor when we were kids who would brag that his bike had more gears than ours. Well, now the landscape has changed, kid. We went from 3 chainrings to 2, and from 2 to single chainring transmissions. In mountain biking, and thanks in large part to the famous SRAM GX shifting group and the Sunrace 11-46 and 11-50 cassettes, the single chainring managed to establish itself relatively quickly. Many of us opted to keep our bikes and, with a few small adjustments, went from 2x10 to 1x11. Other bikers directly changed the entire shifting group or even bought a bike that already had a single chainring transmission.
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They were happy years for the industry, especially for local distributors, who saw their sales of mountain bikes increase thanks to the single chainring trend. The phenomenon was similar to what happened a few years earlier when everyone wanted to swap their 26" wheel bike for one with the new 29" size. Now all of this is coming back to us thanks to Rotor, a Madrid-based company that leads the way in innovation, and has already delighted many with its famous Q-rings oval chainrings, and the—not so recent—Rotor UNO Group.
👉 Should I switch to a 1x12 transmission in mountain biking?
A few months ago, Rotor surprised us once again with a single chainring group, both for road cycling and mountain biking, with a single chainring (to taste) and a 13-sprocket cassette. For mountain biking, it seemed excessive, and for road biking, insufficient. That's how skeptical we cyclists are, and especially the roadies. In September 2019, my colleague Edu and I, along with some friends, visited the Rotor stand at Festibike Las Rozas, and a member of the commercial team from the distributor exhibiting at the event kindly explained to us the reason for the 1X13 Road, which is what Rotor calls the 1x13 road transmission group. Let's analyze the premises and the developments.
What Rotor is selling us
The people from Madrid, both on their website and in the conversation we had at Festibike, strongly emphasize the fact that their 1X13 covers the same maximum and minimum range as a 2x11 system. The correspondences between maximum and minimum development in the 2x11 system (depending on which chainrings and cassette we use) and the 1X13 are clear. I, as an Asturian and a lover of mountain passes, see that I could replace my beloved 52/36 with an 11-30 cassette (9.98 and 2.53) with a 44-tooth single chainring plus a 10-39 cassette. So far, everything looks good, but we need to analyze beyond the extremes.
The intermediate gear ratios
On the road, cyclists seek total comfort during our rides, especially when climbing mountain passes. On flat terrain or descents, we won't have as much trouble, but... what gear jumps do we have between the largest cogs on Rotor's single chainring? Rotor argues that 2x11 drivetrains have 7 redundant gears, as they overlap between the small and large chainrings. Is it true? To check, we can use the Bicycle Gears Calculator. The table on the left shows the gear ratios achieved with a 2x11 setup with an 11-36 cassette and 52-36 double chainring. On the right, the same result for a 1x13 drivetrain with a 44 chainring and 10-39 cassette (the one used by the Rotor Uno group).
For a 700-25mm road wheel, the extremes, although slightly shifted, are very similar. In terms of speed, we see that the maximum speed on flat terrain would be almost 60km/h for the 2x11 group and 55.7km/h for the Rotor 1x13 group. We obtained these figures at a cadence of 100 and, to be honest, I don't think we could maintain more than 55km/h at a cadence of 100 on the flat for long. Therefore, I don't consider this a problem for the Rotor 1x13 group. Now, talking about minimum speed, at a cadence of 60, which is almost the worst-case scenario you might find on a climb, we can see that the Rotor single chainring would actually be even more generous. Extra point, especially for those who dare with feats like the hell of the Angliru or Gamoniteiru. It's clear that the calculator refers to flat terrain, not climbs, but we could extrapolate to a 12% gradient without any problem and keep comparing.
The big problem: gear progression
The main issue with the 1x13 drivetrain lies in the ratios of each cog or sprocket on the cassette. The Rotor group offers jumps in the last 6 cogs from 2 teeth up to 6 teeth, while a 2x11 drivetrain only jumps 2 teeth from the first to the eighth cog and 3 teeth among the four largest. And what do these figures mean? Well, they affect the progression of the gearing.
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Why does progressive gearing make me happier?
The answer is quite simple. Imagine you're climbing a mountain pass like the Connio (La Vuelta 2019, in Cangas del Narcea). It's almost 20km long, with an average gradient of about 5%, with ramps up to 9%. Imagine you're climbing at 15km/h on a 6% gradient. You've already done 10 kilometers of the climb and 60km of the route. You're doing fine, but nothing extraordinary. Your buddy, who always rides his Shimano Ultegra R8000 2x11-speed, suddenly pushes a bit as the gradient changes to 8%, just a little. You're on your brand new Rotor 1x13. At practically the same cadence, he's using a 36-19 gear and you're on a 44-24. What happens when he pushes a bit? He shifts up one cog (2 teeth) and keeps his cadence, but you have to go up 4 teeth (from the 24 cog to the 28), and the increase in cadence, from the comfortable 75 you were at, throws you off. It's true that you can choose not to shift, stand up and push hard. You could even drop 2 teeth to the next smaller cog and show off for a few meters, but unfortunately, it will only be a few meters.
We all know that cadence gives you that comfortable feeling of “I'm suffering but I'm doing fine”. That's where a progressive gear ratio matters, in those small changes in gradient, speed, etc.
Another downside: the price
I won't dwell on this because Rotor has never been a cheap brand. And especially at the technological forefront, the price is usually obscene. Even so, it's worth noting that the complete hydraulic Rotor 1X13 Group, for over €3,500 (with a 10% discount already applied on their website), might seem like one of the most expensive on the market today. But remember it includes carbon wheels and a disc brake group. If you add the frame and peripheral components, you could be looking at a custom bike for around 6,000 euros. Still no joke. On the other hand, let's not forget that the new SRAM Red eTap AXS group with 2x12 transmission isn't cheap either. And it's not a single chainring.
Is it worth having a 1x13 transmission on the road?
The arrival of the Rotor 1x13 groupset to the market is good news for the wealthy enthusiast who can afford to spend over 3,000 euros to upgrade their bike's transmission.
It's a very simple, performance-oriented, and beautiful group. But for those who care about the details, who can feel in the saddle what kind of oil they've put on the chain, I don't think that cyclist will ever put a single chainring on a road bike... Or will they?