By Seb Kemp
Tested: SRAM XX1 drivetrain
In January, 2013 I mounted the XX1 drivetrain you see in these pictures to my Chromag Stylus and went out for a ride. That ride lasted ten months and included a very solid winter of riding (that included The Escape as the drivetrain’s all-weather, all-conditions test), followed by a long summer of rocky, dustbowl riding (that included a trip to Scotland – Angel’s Share). Recently SRAM passed on a brand new X01 drivetrain to test so the XX1 kit has been put into the shed until it finds a new home. So, it seemed like an ideal time to give an appraisal for its long-term performance.
• Single ring, eleven speed drivetrain
• 10 – 42 eleven speed cassette and proprietary XD driver body
• Eleven speed XX1-specific rear derailleur w/ Type 2 clutch
• Carbon fiber crank arms
• X-Sync chain ring design
• XX1-specific eleven speed chain
• Eleven speed trigger or Grip Shift compatible
• XX1 group price: $1449 – $1573 USD
What's the big deal with XX1? Well, it quite simply is the most secure and versatile drivetrain currently available. After thousands upon thousands of feet of descending, most of it done on rocky and mucky terrain throughout the winter and summer of British Columbia, not once did the chain drop. The XX1 chainring has a unique hook and crosshead tooth profile that holds the chain in place. When paired with the Type Two clutch derailleur chain slip and chain slap disappears.
I was half expecting the teeth to lose their hold on the chain after some wear. However, despite one of the grittiest test cycles I've ever put a drivetrain through (and perhaps the laziest maintenance schedules I’ve ever managed to achieve – aren’t hardtails brilliant?), everything still held on tight. The 30-tooth X-Sync sprocket after about a zillion revolutions shows wear but surprisingly no more than would be expected to happen to a regular chainring. There has been considerable wear on the front side of the cross-headed teeth and if the drivetrain hadn’t been replaced then it would certainly be time for a new chainring. However, the chainring had still not dropped a chain, something which some X-Sync imitators can’t manage even after a month of riding.
The muddy conditions did present a different problem, however: the profile of the chainring and derailleur jockey wheels (also highly sculpted) meant dirt easily adhered to them, necessitating regular cleaning, including occasional mid-ride muck removal. Throughout the summer this was not a problem and shifting and drivetrain smoothness was excellent, but as the trail conditions slide back into wet season the drivetrain did tend to gunge up somewhat.
But the XX1 drivetrain doesn’t just excel at chain management. If chain security and pedaling efficiency was your only concern then going single-speed would be the only option. However, we don't all have the meat and mettle to push one gear uphill, which is where that huge cassette comes into play.
SRAM haven’t just added an eleventh gear. The spread of the cassette accommodates gears from 10 to 42 teeth. This gives a very wide spread of cogs that, although not as big as a multi-ring setup, still gives a very useable and appealing top and bottom gear. The 42-tooth sprocket paired with a 30-tooth chainring (a new bolt pattern allows down to a 28 tooth chain ring to be used) gave me all the granny gear I needed to wind myself up any non-IMBA standard climb within sight. For long midsummer days of climbing in the backcountry I did slip on a 28 tooth chainring (something which is made extremely easy to do because the crank spider is offset so you don’t need to remove the drive side crankarm to change the ring). This provides the same ratio as a small 24 tooth chain ring and 36 tooth cog that comes as standard with many triple setups. However, as some people point out, this compromises a top-gear for absolute pedal hammering speed. Well, personally I don’t ride any single track that would ever necessitate such big-ring spinning but I know a few roads that might. But I suppose that’s why I mountain bike rather than road bike. Horse for courses.
The shifting is crisp and quick shifting, but it must be noted that it is not as quick as Shimano. Partly this is because the shifts don’t initiate on the compression of the shifter like Shimano’s does, but also because it doesn’t have the double-down shift you get with “long pressing” Shimano shifters. Shimano does take the lead on speed shifting, if only SRAM could incorporate this into it’s design.
The derailleur, although ugly, is incredibly tough. It shrugged off some huge direct hits that made me cringe and expect the worst. Instead the derailleur proved its everyday worth. A gripe would be that the roller bearing Clutch on the derailleur does tend to dry out and bind all too often. Sure, a drop of lube helps loosen the stiffness but on longer rides it would still tighten up. It is a good idea to just keep on top of giving it a check up and the occasional lube.
SRAM have admitted that it's feasible that the technology of XX1 will trickle down to lower price points in the future. We have already seen the X01 drivetrain being released, but this still doesn’t make it accessible to everyone as the pricing between the two groups is still quite close. Once some manufacturing challenges have been solved (in particular, developing a cheaper means to produce the cassette) then expect to see single ring, eleven-speed drivetrain a lot more places. This means more riders will be able to benefit from having a simpler and more efficient drivetrain.
In conclusion, it's still the same old drivetrain system we have had since the late 1800s, but XX1 is its biggest evolutionary step forward in a long time. It is simple, silent, reliable and rather resilient to real world use. All things you don’t normally expect from a boutique drivetrain. In short, I would find it hard to go back to anything else now.