Tugging on steel cables to change gears might sound a bit archaic, but modern drivetrains perform pretty damn well these days. We've got single chainring setups that deliver over 500-percent range, don't require a guide, and are relatively reliable and lightweight. Life is good.
Rotor thinks it could be better, though, and their approach uses hydraulic fluid instead of a cable, and a massive 10 - 52 spread, 13-speed cassette that should provide enough range for any rider and any mountain.
The mountain bike version of the 1x13 derailleur will include a clutch system, too.
The Spanish brand has been using hydraulic fluid for their Uno system for years now, although I bet you're more likely to see a Sumatran Rhino in the wild than an Uno drivetrain. Rotor's taken what they've learned with Uno and applied that to their 1x13 system, but they've also designed it to be extremely modular and ready for all sorts of uses: it can be set up as a 1x12 or 1x13 system with four different cassettes, and be used on road, gravel, and mountain bikes thanks to different shifters.
I know what you're thinking: Why the hell do we need 13 cogs? Well, we obviously don't need 13, or 12, or 11, or even 8 cogs to enjoy riding, but more cogs can mean smaller jumps between each gear, which is an important point when you're looking at a 10 - 52 spread cassette.
Rotor's 12-speed cassettes are compatible with a normal freehub body due to how the 10-tooth cog hangs off the end of it, but you know it's a different story when you add another cog onto the stack. To make it work, they've come up with their own hub (and freehub) design, and the drive-side spoke flange sit a touch more inboard than on a standard hub. This provides the necessary room, but the tradeoff is spoke angle, of course. Whether that matters or not is yet to be seen.
If you want to run the 13-speed cassette, you'll need to use Rotor's hub that sees its drive-side spoke flange moved inboard and a proprietary freehub.
Their 13-speed cassette uses 12-speed cog spacing, too - the cogs don't sit nearer to each other - so riders can use a standard 12-speed chain, and it shouldn't be any finickier than what's currently on the market. Of course, that'll mean different things to different people depending on how 12-speed is working out for them.
The derailleur that Rotor had on display looked every bit the prototype that it is, with machining marks and a rough finish on it, but it also has a few extra screws compared to what we're used to seeing.
Rotor has designed-in derailleur throw stops of sorts that determine how many gears you can shift with each push of the thumb paddle. So if you wanted to have it so one push equals one cog, you could do that; if you want to be able to run through four or five cogs with a larger push, you can set it up to do that, too. There are also the normal limit screws, of course.
Not only that, but you can also run the shifter with just a single paddle that controls shifting up and down the cassette depending on how far you push it or go with a more traditional two-paddle layout. I think that really underlines what could be the advantage of Rotor's new drivetrain: With four different cassettes and the ability to set the shifter up a few ways, you can run their 1x13 drivetrain whichever way best suits how, and where, you ride your bike.
Weights and an MSRP are still up in the air at this point, but Rotor says that the plan is to have it come in around SRAM and Shimano's high-end offerings on both fronts.