SRAM’s 12-speed MTB group: making sense of the gossip

Wider range gearing is on the way, but what does it mean for you?

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.

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As you may be aware, leaked photos are floating around the backwaters of the internet of a soon-to-be released 1×12 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?

The rumored range is a whopping 10-50t, but the exact gearing is still a secret:

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 1×11 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 1×11 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 1×11 drivetrain with the rumored 50t added for good measure:

The percentage jump between gears of the current SRAM 1×11 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.

Competition from shimano, as well as from aftermarket add-on cogs and cassettes may have spurred the development of sram’s 12-speed group. 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 :

SRAM may have been first, but there is plenty of 1×11 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 2×10 or 2×11 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 1×11 drivetrain and Shimano advises against it. We included it in this graph for the sake of comparison.) 

Here’s how the rumored sram 1×12 group might stack up to the competition in terms of gear range:

Here’s how SRAM’s 1×12 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 1×11 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 1×11 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 1×11 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.

A 1×12 drivetrain could mean more companies will release full suspension models without front derailleur mounts, such as the recently-released santa cruz hightower:

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. 

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Whatever SRAM has up its sleeves, we’ll know the facts in short order.