First impressions of the 1x11 mountain bike groupset
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While radically different in appearance, the new XD freehub body isn't really all that different from a standard SRAM/Shimano driver. The end is cut off, most of the splines are milled down, and new threads are added to the base. Otherwise, the axle interface is carried over so that manufacturers don't have to completely redesign their hubs.(Image credit: James Huang)
The SRAM XX1 trigger shifter internals are based on the X0 shifter but the look and feel are more like XX.(Image credit: James Huang)
A standard SRAM X0 rear derailleur upper pulley is offset from the pivot by about 7mm. The new SRAM XX1, however, is offset by at least 30mm by our estimation so that the chain gap can automatically adjust for different gear ratios without requiring a slanted parallelogram.(Image credit: James Huang)
The new SRAM XX1 rear derailleur uses what the company calls a 'straight P' geometry with no slant to the parallelogram. According to SRAM, this results in fewer ghost shifts in bumpy terrain. Proper chain gap is ensured by the massively offset upper pulley.(Image credit: James Huang)
SRAM includes the Type 2 roller bearing cage into the XX1's carbon fiber cage.(Image credit: James Huang)
The new SRAM XX1 crankset is lighter than XX by virtue of having just one chainring but the arms themselves are actually bigger and heavier. Note the asymmetrical bolt circle pattern, too, which allows the chainring to slide out around the crankarm for easier ratio changes while also virtually guaranteeing that it can't be improperly installed.(Image credit: James Huang)
We'll have to wait until we get our long-term test group to gauge chainring durability While the sides of these teeth are clearly wearing from the chain, we also don't know exactly how many miles are on this setup, either.(Image credit: James Huang)
The synchronized teeth mesh perfectly with the new SRAM PC-XX1 chain and they're also extra tall for secure retention. In most cases, SRAM claims no guide is needed and our initial test ride seems to support that.(Image credit: James Huang)
Threads are integrated into the SRAM XX1 chainring for easier installation and removal. Note how the chainring is backed by tabs on the spider, too, removing much of the load from the bolts themselves.(Image credit: James Huang)
The new SRAM XX1 cassette doesn't use a lockring so much as a locking tube. The threads are built into the base of the driver body, not the end.(Image credit: James Huang)
The largest cog is dished more than the standard XX cassette, allowing 11 gears to fit on what is effectively a 10-speed driver body.(Image credit: James Huang)
The largest cog is a pressed-on aluminum piece that also includes the spline interface for the new XD driver body. There's more than enough room for mud to pass through.(Image credit: James Huang)
The new SRAM XX1 cassette features a massive 10-42T range and similar machined construction as the standard XX unit.(Image credit: James Huang)
Of course, SRAM's new XX1 trigger shifter is compatible with MatchMaker X mounts for a tidy appearance. There will also be a Grip Shift option as well.(Image credit: James Huang)
They say patience is a virtue, though, and our first impression is that the groupset was worth the wait, and that reasonably fit trail riders should find the range more than adequate. It's light, it looks good, it's quiet, it's secure and, most importantly, it just flat-out works.
One chainring but plenty of range
Our Specialized S-Works Enduro loan bike was equipped with a 34T chainring as we headed out for a spin around Whistler's Lost Lake trail network. While there were no huge climbs or bomber downhills, there were still plenty of shorter – but reasonably steep and technical – ascents and fast, attention-demanding descents, including part of the Crankworx Enduro course.
Shifts are quick and precise, with XX-like chain movement across the cassette even under load. We were never at a loss for gears despite having just one chainring. In fact, we probably could have gone with the 36T option and been comfortable. Moreover, none of the individual jumps on XX1's massive 10-42T cassette are disruptingly big, and they're admirably even across the spread.
The new sram xx1 cassette features a massive 10-42t range and similar machined construction as the standard xx unit:
XX1's total range can't match SRAM's current 2x10 offerings. But, then again, that's not the goal (more on that later). Chainrings will be available from 28 to 38 teeth in two-tooth increments, and the idea is that the user will choose the gear range 'window' that best suits the task at hand. For example, we can easily foresee gearing down to a 32T chainring for the big mountain climbs of our US office in Boulder, Colorado. Meanwhile, folks with a more rolling landscape could probably get along fine with the 36T or even the 38T variant.
To ease gear swaps, the XX1-specific bolt circle diameter is designed so that chainrings can easily fit around the crankarm and spider (meaning you won't have to pull the driveside arm). There are integrated threads on the chainrings (meaning fewer parts to lose) and the bolt pattern is asymmetric so it's impossible to install the ring incorrectly.
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Clever tooth profiling
More than a few editors on site were concerned about the lack of a chain guide on our test bikes, especially considering the 11-speed cassette's broader range of chain angles compared to a standard 10-speed setup.
Nevertheless, none of us had any chain retention issues, and it's hard to derail the chain up front manually given the tall, slightly hooked and alternatingly indexed 'X-Sync' chainring tooth profiles that hold onto the new PC-XX1 chain with impressive tenacity.
In fact, a separate test crew from another publication rode their similarly guide-free XX1-equipped bikes down Whistler's far more demanding Top of the World trail and had no issues – to the point where one editor insisted that SRAM had embedded high-power magnets into the CNC-machined aluminum chainring (alas, there are none).
That being said, SRAM still admits that a guide might be necessary in more extreme conditions. For example, while sponsored rider Jerome Clementz showed up to join our ride sans guide, he used one to win the Crankworx Enduro a few days earlier.
SRAM has also integrated a similar, but less extreme, tooth design into the rear derailleur pulleys. While chain retention generally isn't an issue back there, we noticed how quietly the system runs – even in the 10T and 42T gears. Because XX1 is optimized for a single ring, the chainline is perfectly positioned in the crank.
Moreover, the inclusion of SRAM's Type 2 one-way clutch for the pulley cage virtually eliminates chain slap. Plus, a new finishing process on the PC-XX1 chain supposedly improves elongation wear by four times compared with the company's current 10-speed chains, despite narrower rollers.
Trigger or twister options
SRAM will offer XX1 with both trigger and Grip Shift shifter options. We sampled the former, and while its mechanics are supposedly more closely related to X0, the look and feel are more akin to the standard XX unit. Clicks are easily audible, with good tactile feedback overall, albeit with a little tinniness compared with Shimano's more substantial feel.
As usual, each downshift push moves the chain across a maximum of three cogs, while the release trigger does one at a time in rapid-fire succession.
Obviously, XX1's 1x11 configuration includes no front shifter. Weight and simplicity benefits aside, riders who run dropper posts will now be able to run remote levers in a more ergonomic position, beneath the bar. And when things get hectic there's also one less set of controls to juggle.
Clever tooth profiling
As previously mentioned, the new XX1 cassette will only mount to the new 'XD' cassette body, which is currently offered only by SRAM, Mavic and DT Swiss. It's worth keeping in mind that a number of companies use DT Swiss freehub bodies in their own wheel designs, though, greatly expanding the collection of compatible offerings.
While radically different in appearance, the new xd freehub body isn't really all that different from a standard sram/shimano driver. the end is cut off, most of the splines are milled down, and new threads are added to the base. otherwise, the axle interface is carried over so that manufacturers don't have to completely redesign their hubs:
According to SRAM's drivetrain product manager Chris Hilton, a "very, very long list" of other companies have already signed on as well. This means consumers shouldn't have much of an issue finding retrofittable bodies to mount on existing wheels, especially as the design doesn't require changes to the axle interface, unlike Shimano's new 11-speed Dura-Ace group.
Interested parties can check out SRAM's dedicated site for more information on XD, including detailed drawings and licensing info.
What's the point?
Hilton readily admits that XX1 isn't for everyone, but for those who are already using 1x drivetrains – or have considered it – the new group certainly expands the versatility range and decreases some of the technical barriers to entry. Performance riders will enjoy a more straightforward drivetrain, with none of the mechanical headaches commonly associated with multiple chainrings, more chainring clearance (plus, the teeth are never exposed to rocks and logs) and less parts to fail.
From a manufacturer's perspective, there are also the side benefits of not having to worry about front derailleur placement (meaning chain stays can be shorter and more widely spaced, for better handling and tire clearance) or the effects of multiple chainrings on suspension performance. In addition, the 1x11 concept is just simpler to operate.
We're currently waiting for confirmation on XX1 costs. Granted, the premium pricing (roughly between XX and X0 in terms of total group cost) will put it out of reach of the masses, but it's inevitable that SRAM will expand the idea to lower price points.
SRAM doesn’t expect 1x11 drivetrains to completely supplant 2x10 ones – and neither do we. Nevertheless, we don't see any downsides at the moment, aside from the slightly narrowed total gear range.
Needless to say, one ride of SRAM XX1 wasn't enough, and we're aching for more saddle time.
Production XX1 bits should begin shipping in October.
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