SRAM Takes it to 12

So the news is well and truly out; SRAM is making the leap to 12-speed with the release of the new Eagle drivetrain. With a massive 10-50 cassette, it offers a 500% gear range — this just about matches the gear spread offered by a Shimano 2X11 drivetrain and it’s not that different to the old-school MTB triple.

With this SRAM is calling the ‘death of the front derailleur’ and some will certainly find the 12-speed system appealing; it achieves the gear range of a multi-ring drivetrain with the simplicity of a 1X setup. With this there’s less weight, more handlebar space for a dropper post, fewer cables and no shifting between chainrings.

The new 12-speed Eagle drivetrain will be offered in two variants; XX1 Eagle will be the lightest option that’s aimed at XC/trail use while X01 will be aimed at all-mountain/enduro applications with more robust cranks and fewer titanium/carbon bits. Aesthetically, the lighter XX1 Eagle can be identified by its gold highlights while the X01 Eagle has red highlights, although both also come in all-black if you prefer a stealthy look.

While the move to 12-speed mandates a new chain, cassette, shifter and derailleur, it doesn’t require any new frame or wheel standards. It can be fitted to almost any modern MTB with a 135mm QR, 142mm thru-axle or a boost style 148mm rear axle. All you need is a SRAM XD driver body on the freehub, a system that’s available for many wheels these days.

The new cassette mimics the ratios offered by the current 10-42 SRAM 11-speed cassettes with the additional 50 tooth dinner plate serving as the 12^th cog. So how did SRAM manage to shoehorn in an extra cog without changing the hub spacing or altering the freehub?

Well the 10 tooth cog sits in the same position but the cog spacing drops from 3.8mm to 3.65mm. As a result the second biggest (42T) cog is a little further away from the spokes. The 50 tooth cog sits a little further inboard than before, but its massive diameter (roughly equivalent to a 180mm disc brake rotor) means that there’s still sufficient clearance between it and the spokes.

Overall the chain line sees more variation than a 1X11 drivetrain but the 1x specific 12-speed chain has been redesigned to handle the demands, in fact SRAM claims the new Eagle drivetrain is quieter and smoother running than their previous systems. More than just an extra cog, the Eagle setup features a broad range of refinements that have come from SRAMs experience with making dedicated 1X drivetrains.

Chain

This component really is the key to SRAMs new 12-speed setup. Where an 11-speed chain measures 5.6mm across, the Eagle chains are 5.25mm. Previously the pins protruded by 0.1mm on each side but the new chamfered outer plates allow the pins to sit completely flush. This accounts for 0.2 of the 0.35mm width variation between 11 and 12-speed while the countersunk pins are said to lock more securely into the outer plates to make the chain stronger. The profile of the inner plates has also been redesigned. It’s no longer shaped with front shifting in mind and SRAM claims smoother and more durable as a result. These tweaks along with updates to the rollers and a new titanium nitride coating have SRAM claiming this to be, “the quietest, strongest and most wear-resistant chain in the world.”

Once again SRAM employs a tool-free joiner to connect the chain; for 12-speed it’s called the ‘Flow Link’. As with their nine and 10-speed joiners, it’s a single use item and should be replaced whenever the chain is removed and refitted.

Derailleur

While it clearly follows similar lines to their existing 1X specific models, it has a wider capacity to handle the 12-speed cassette. The cage itself is marginally longer and the lower jockey wheel is larger with 14 teeth. Both changes increase the derailleurs ability to take up chain slack and allow it to function across the massive 10-50 gear range. Additionally, SRAM employs a new ‘Type 3’ clutch mechanism that’s said to be smoother and quieter (less likely to encounter the Type 2 knock we’d suspect). Finally, the ‘cage lock’ button has been moved to make it less prone to trail damage. 

Shifters

Both triggers and gripshift will be offered to suit the new Eagle groups. Again the changes go deeper than simply adding an extra click and the trigger has a new internal mechanism that’s said to be smoother and more precise. It’s around 10g heavier than before (122g for Eagle XX1 versus 110g for XX1) but still features an adjustable pull lever and mounts via their integrated MatchMaker X system.

Cranks & Chainrings

With its alternating wide/wide teeth, the original X-Sync chainring was a key part in SRAM’s push into 1X drivetrains but for Eagle SRAM has introduced ‘X-Sync 2’. While it still has alternating wide and narrow teeth, the individual tooth profiles are more elaborate and uniquely sculpted. The new design is said to run quieter and offer substantially better wear resistance; definitely a bonus on 1X systems as chain wear is no longer split between a number of chainrings. These chainrings utilise the same direct mount spline, so they will be compatible with older SRAM cranks.

The Eagle XX1 cranks feature new hollow carbon construction and weigh 465g for the arms and direct mount chainring. That’s 81g less than the regular XX1 crankset and approximately 33g heavier than a RaceFace Next SL crankset (a benchmark that we often use when comparing lightweight cranksets).

For heavier use SRAM builds the X01 Eagle cranks with additional carbon around the ends for better rock impact resistance and a foam filled core. The result is still lighter than the regular XX1 cranks at 495g (without the bottom bracket).

While there will be different chainring offsets to suit regular (49mm) and boost (52mm) systems, there will no longer be variation in the chainring offset for 24mm GXP and BB30 bottom bracket systems — nice to see a bit of simplification happening here!

Cassette

Most SRAM users will be well familiar with the gear ratios offered by the Eagle cassette; aside from the 50T they’re identical to a regular 10-42 11-speed cassette. Jumping eight teeth from the 42 up to the 50 may seem radical but it produces a 19% change in gear ratio; that’s slightly smaller than the step that you get when shifting from the 10 to the 12 cog at the other end of the cassette. Have a look at the gear chart below and you’ll see how the ratios compare to SRAM 11-speed as well as a Shimano 2X11 drivetrain.

 

In this chart we’ve shown the Eagle drivetrain with two chainring options; a 32 as that’s what people commonly run with 1X drivetrains as well as a 36 tooth chainring. With this you can see that the 32x42 gear combination provides a similar climbing gear to a 36 tooth chainring with the Eagle cassette; you just gain a taller top end for fast fire road pedalling. Alternately, running a 34 tooth chainring would offer an increased range at both ends of the spectrum — it’s your call as to how you utilise the added gearing range.

Weights & Aussie Pricing

Overall the Eagle drivetrains carry similar pricing to the existing 11-speed parts, with one main exception. The 12-speed cassette will set you back around $699 which is about $100 more than the 11-speed equivalent. Aside from that the Eagle XX1 derailleur will be $479 (around $20 less than XX1), the trigger shifter is $279 and the new XX1 cranks will go for $699. At this point we don’t have Australian pricing on the 12-speed chain but it should be too much more than a regular SRAM 11-speed chain.

When compared to 1X11, most components have gained a handful of grams but the cranks are lighter which reigns in the difference. Overall the weight gain is relatively minimal and it remains a good deal lighter than a multi-ring drivetrain. Here’s a breakdown using the XX1 Eagle and 11-speed XX1 as an example:

	XX1	Eagle XX1	Weight Difference
Cranks	546g	465g	-81g
Trigger	110g	122g	+12g
Rear Derailleur	245g	264g	+19g
Chain	252g	250g	-10g
Cassette	268g	365g	+97g
	1,421g	1,466	45g more than 1X11

 

Production for the Eagle drivetrains is scheduled to begin in May 2016 and we’re expecting to see limited availability within Australia by June this year. 

Scroll down for the Eagle launch video and the full specs for both drivetrains.