By Eric McKeegan
Spreadsheets. I hate them. But when I sat down and made one to compare the SRAM XO 2×10 drivetrain’s gear ratios to a standard 3×9, a few things really stood out to me. But that’s getting ahead of ourselves. Let’s get an overview before delving deeply into the netherworld of gear charts.
The XO group is the more all-purpose group at the high end of the SRAM line-up, a step down in price from XX. Where the XX group is aimed at XC racing and trail riding, depending on configuration, XO should be at home on everything from XC race weapons to all mountain brawlers, and even DH bikes for those looking to save some weight. (Note, SRAM recently unveiled downhill-specific XO cranks, chain guide and a short-cage rear derailleur.)
To me, the cranks play a starring role in the new XO group. Carbon fiber, with aluminum inserts for the pedal and bottom bracket spindle interfaces, the center of the arm itself is hollow (or as hollow as something can be with non-structural foam inside). Even with no metal skeleton, the XO crank passed all kinds of tests for strength, and when pushed to failure, the bottom bracket spindle bends before the carbon breaks, a nice thing to think about when charging that next drop off.
Currently, the chainring options are 26-39 (aimed at all mtn/ trail/29ers) and 28-42 (XC race and fit folks), but the removable spider and product shown at Interbike indicate more options on the horizon. And yes Matilda, you can get a triple (soon) in the 22-33-44 flavor. The double is a new chainring BCD size, namely 120/80. No way to mount a bash guard on the double either, although a BB or ISCG mounted one would do the job fine.
Out back, the 36-tooth cog on the cassette is aluminum and serves as the spider and cassette body interface for the seven largest cogs. The rest of the cogs are steel, with the smallest three being separate from the carrier.
Both front a rear shifting require care when setting up, in particular, getting the upper pulley 6mm under the big cog in the rear, the B-tension screw is your friend here. Once set up properly both front and rear need little to no finagling to stay in adjustment.
Front shifting was pretty darn snappy, to the point where I would shift chainrings anytime with no grimacing from either the components or myself—easy shifts to the big ring, and no problem snapping to the small ring even while under power. No chainsuck either, even through some really crappy late winter moto trail sessions. I think they are mighty stiff too, but I’m not one to dwell on things like that.
Out back the medium cage rear derailleur went about its business with nary a whimper. I also noticed less of a tendency to get more shifts that I wanted, something that used to happen pretty regularly after a stint on lighter-action Shimano shifters. No loss of the very positive click detents between gears, but less chance to push too far past them and get an extra shift.
Shifting on components of this level is expected to be very good, and XO didn’t disappoint. The real question, at least for me, was about the gearing range. While I’ve spent plenty of time on singlespeeds, I also have been appreciating the gear range of a triple as my test bikes all seem to weigh around 30lbs. with increasing amounts travel. Back to those spreadsheets and charts, I discovered the 2×10 with a 26-39 only gives up the very easiest granny gear, and two of the hardest on the fast end. Personally, I don’t think I’ve ever used a 44-11 off road, so I didn’t miss the big combos, but after riding for most of the review period on 29×2.4” tires, the resulting gear inches (with the 26-39 crank) made me miss the easiest gear for scrambling up the loose steep stuff. I did switch the XO group to a shorter travel 26” bike at the very end of the review, and initial rides lead me to believe the gearing will be well suited to this application.
In everything but the steepest stuff, 2×10 was great. With only two rings, the whole cassette range was available with no worries about cross chaining. Which meant less front shifting, although without a granny I was much more apt to shift the front and not worry about chainsuck or tossing the chain over the small ring while shifting under power. The 26 has most of the usable range of a 32 (You run the 32-11 much? No? Me neither), and most of the time, the late season sloppiness kept me down in the low range anyway.
The XO-branded brakes are pretty close to the Avid Elixir CR, but forgo the tool free reach adjust dial. They still have the nice pad contact adjuster, making it easy to get the brakes to feel like you want. I’ve come to really like these brakes, just the right balance between modulation and power. The carbon levers have a nice shape, and a perfect hook for one-finger braking.
The rear derailleur is available in three cage lengths (for 1, 2 or 3×10 setups) the front derailleur is available to fit the many options out there. Brakes are available with 140,160, 180 or 200 mm rotors, and cranks are available with an aluminum 30mm (BB30, PF30) or steel 24mm spindle (English or Shimano press fit style BB) with bottom brackets to match.
There is no doubt XO is a very, very good mountain bike component group, the question really is: where does 2×10 fit in? For XC racing applications, I predict the triple will be almost extinct in the pro and expert ranks in the next few years, save for some endurance events. For the rest of us, a typical triple crank set up has the advantage of a big enough gear range to work for just about any rider, on just about any bike, on just about any terrain. But with all that versatility comes redundant gears and extra weight and complexity. Two chainrings simplify things, improves front shifting performance and has most of the usable gear range of a triple. The 2×10 system isn’t limited to the high end anymore either; both the X7 and X9 groups are available with similar options.
Personally, I’m pretty stoked on the 2×10 idea, and with more double and triple chainring options in works, I see less gears on more bikes in the future