Update! It's been confirmed and we've ridden it! SRAM's 12 speed Eagle drivetrain is official! Read about it in the links below.
As you may be aware, leaked photos are floating around the backwaters of the internet of a soon-to-be released 1x12 speed SRAM drivetrain with a whopping 10-50t range. SRAM has declined to comment publicly on any of our questions about this group, but let's assess what this drivetrain might mean for mountain bikers when it’s released.
What's between the little ring and the granny gear?
While the range of this drivetrain appears to have been leaked, the exact tooth counts between 10 and 50 remain unknown. Is it possible that SRAM would simply carry over the tooth counts of its 1x11 drivetrain with the addition of a 50t cog? It's not only possible, but likely.
The leap from a 42 to 50t cog is a rather large jump, 19 percent, to be exact. However, this is not out of step for SRAM; consider that there’s a 20-percent jump from the 10 to 12t cog, and a 17-percent jump from 36 to 42t on SRAM's current 1x11 cassettes. There must be large gaps at some point on a 12-speed cassette with such a wide range. It might make sense to put them at the ends of the cassette. Afterall, the 50t cog is a bail-out gear if ever there was one.
So let’s assume the steps carry over with a 50t cog. If this proves to be the case, the tooth count would look like this: 10-12-14-16-18-21-24-28-32-36-42-50.
The percentage jump between gears of the current SRAM 1x11 drivetrain with the rumored 50t cog added for good measure
A single-ring drivetrain to silence the doubters
This 12-speed cassette would have an expansive 500 percent range from the lowest gearing to the highest. Compare that to SRAM’s 11-speed mountain cassettes, which have a 420 percent range.
SRAM may have been first, but there is plenty of 1x11 competition these days. From left to right: OneUp's 44t add-on cog for XX1 and XO1 cassettes, e*thirteen's 9-44 TRS+ cassette and Shimano's 11-42t XT cassette
The massive range of this drivetrain would make it a serious contender with any 2x10 or 2x11 drivetrain. Here's how it would stack up against Shimano's 11-speed drivetrains and popular aftermarket add-on cogs and cassettes. (It's worth noting that while it's possible to run Shimano's 11-42t XT cassette with a double crankset, it was designed for the 1x11 drivetrain and Shimano advises against it. We included it in this graph for the sake of comparison.)
Here’s how SRAM’s 1x12 group would stack up against the competition in terms of gear range
How to fit another cog onto the cassette?
Cog spacing is a critical unknown. Will this new group use the same spacing as current 1x11 drivetrains? Will this new cog simply fit inboard of the 42t sprocket without interfering with the spokes? It might be possible to fit another cog, particularly one as large as a 50t, inboard of the freehub body in the same manner as the 42t sits on current SRAM 11-speed mountain cassettes.
So what could all this advancement mean for the average rider?
A few things, actually. First off, it would mean cheaper prices on SRAM's current 1x11 kits. We're already seeing significant discounts on SRAM's top-tier XX1 transmission. Bargain hunters should also check out SRAM’s recently-introduced NX group, the most affordable 1x11 drivetrain yet.
Additionally, if you've been put off by 1x drivetrains in the past, maybe because you tried a single-ring system and found your legs lacking, or maybe your terrain is just too dang steep, the extended low range of this new group might make it a viable option for you. Or perhaps you always had the legs but felt 1x options limited your speed range too much, here the solution could lie in a wide-range 12-speed cassette matched with a larger chainring.
More companies will probably release full suspension models without front derailleur mounts, such as the new Santa Cruz Hightower
A broader 12-speed drivetrain probably won't spell the end of the front derailleur, although it does mean that more companies will introduce full suspension frames that are not compatible with front derailleurs. One suspension designer BikeRadar spoke with, who is currently working on 2018 model year projects, confirmed that front derailleur mounts were no longer part of the equation, as far as their projects are concerned.
Whatever SRAM has up its sleeves, we'll know the facts in short order.