When we first saw SRAM’s XX group at Interbike, we were quite excited to be honest. It was the most exciting thing to happen since our first ride on a RockShox Mag 21. And trust us, we wanted to ride it as soon as we saw it. It just made sense -- lighter, cleaner, simpler.
With its debut at the show and the media frenzy that followed, the XX components became fodder for the industry rumor mill -- namely, we began to hear reports that frame compatibility was an issue. While we awaited more information regarding crank and front derailleur fit particularly, we found our own preliminary answers by building templates to XX crank specs and test fitting every frame we sell with 6′ or less suspension travel. Once we had the real deal in our grubby little hands we test fit the XX cranks and bottom bracket on all of our bikes to see what did or did not fit. What we found was that the Q166 crank fits damn near everything under the sun, and the Q156 crank fits a surprising many as well. Now that we’ve dispelled the myths and ridden the proof, here’s what we know:
1. Q-factor? Isn’t that a road thing?
Our testing provided indication that XX could be installed on nearly any bike we could think of. We now have the confidence to say that the Q156 crank will indeed fit most hardtails and many of the full-suspension frames we sell, and the Q166 will fit everything we sell in the <6' category. Everything.
Most experts agree on the importance of Q-factor, the width of the crankarms where the pedals attach. Anatomically, a narrower Q-factor more closely matches the nearly in-line track of human footsteps. All of the aforementioned confusion stems from the effort by SRAM to create multiple Q-factor options for their XX crankarms.
Due to geometric differences between road and mountain bike frames, along with the evolution of the modern mountain bike components, we now see major differences in Q-factor between road and mtn. groups. For example, road crank Q-factors generally fall within the 146-152mm range. Most mountain cranks are 170mm and beyond. The narrow XX crank comes in with a 156mm Q-factor. We see this as an advantage to the crossover road/mountain bike rider. For folks that spend time training on both bikes, replicating positioning could be the difference between a championship and a season nursing a sore knee.
Otherwise, the XX crank gives some of us relief (similar to the advantage of BB30 road cranks) from the dreaded crank rub. If your crankarms are polished to a fine luster, then your cleat/foot position necessitates more room for ankle clearance. The double ring setup on XX cranks brings the spider towards the bike centerline, at the same time tucking in the crankarm some number of millimeters. Put honestly, our XT cranks are polished and our XX cranks are not. We’re not going to change our position. After all, why risk a funky repetitive motion injury if all is well as-is. But we’ll take a reduction in frictional loss for sure! Less friction, no matter where you eliminate it, is faster. We like that.
2. Big-biggers rejoice!
All it takes is one good, hard ride to fall in love with XX. We were surprised at the sensitivity of the carbon trigger shifters. We found ourselves a little ham-fisted at first, but ten minutes into the ride, we were adjusted to them. They are more responsive than anything we’ve ever felt. The rear shifter can be double clicked, literally, like a mouse, and the corresponding shift at the rear derailleur is instant and flawless, as if you merely shifted once. Someone with a deft right thumb could swing the rear derailleur up six cogs on the cassette with one push.
XX takes front shifting to Dura-Ace levels, and no, we’re not still intoxicated from our last ride on the stuff. SRAM talks of X-Glide technology. All we can say is the ramps and notches on the big ring do their job exquisitely. The smooth shifting to the big ring under pedal load was one of the most impressive functions. We never heard chain rub on the inside of the front derailleur cage when we were cross-chained either direction. This is due to the optimized chainline at 50mm and to SRAM’s decision to move to two chainrings, which simplified the whole package.
We found ourselves re-adjusting to the gear ratios offered on the XX, as 3×9 gear ratios are intrinsic to us now. After a few minutes, the XX started to make more sense. On subsequent rides, we found the two chainring setup to offer everything that we needed. Make no mistake, XX is a full on mountain bike group. It just shifts akin to our beloved road bikes.
3. Redundancy is excessive and needless
The folks at SRAM realized that too many gear combinations on a standard 3×9 setup were the same, or nearly so. So why continue with the physical and functional burdens of the third chainring and the extra length of chain required? XX does a better job with less. Want to see an exercise in minimalist functionality? Take a good look at the Matchmaker-X. It combines brake, shifter, and fork lockout all in one simple and super- lightweight package -- the ultimate in integration. Again, why have three clamps on the bar when you can have one?
4. Is this the David to XTR’s Goliath?
If competitive cyclists (not just us) were polled, people in the know would most likely have checked XTR as their go-to group for a race bike. XX may well write the chapter where SRAM gets that check. Of course, it’s a 2×10 so it’s easy to focus on the drivetrain components. The rest of the group is accordant, and features like the new 2-piece brake rotors (including Centerlock options), magnesium caliper body, carbon shift and brake levers, and Ti hardware shouldn’t be overlooked either. Also, the rear derailleur and bottom bracket are equipped with SRAM BlackBox ceramic bearings as standard equipment. In fact, one of the details we really appreciated was the rear derailleur cable termination. Nothing says amateur like cables that look like curb feelers, and the inner wire on the XX rear derailleur clamps on the back of the parallelogram. The free end of the wire can be trimmed to lie just inside. Say goodbye to frayed cable ends.
5. It’s lightweight and smart
The XX group saves weight by leaving bits off the bike instead of taking bites off the bits on the bike. They didn’t sacrifice the material strength of any part in the group. In fact, when one stands before it, XX looks pretty studly, like it could take a good beating. When we compare the weight of the new XX drivetrain components with the current XTR analogues, XX comes up an amazing 345 grams lighter. That’s the weight of an XX front brake and a pocket full of GU’s. Yes, XX tallies for some $400 more, but the weight saved to dollars spent ratio is better than the jump from XT to XTR. And you get a performance boost to boot.
6. Fear not, the untrod path.
SRAM, with their XX group, is certainly not the first to sing the praise of two chainrings. However, it seems that with their development of the 10-speed mtn bike cassette and with their devotion to it, they’ve made it work very well. New technologies like their X-glide shift points and their Exact Actuation make it all work seamlessly. The new XX fork lockout is worth more than a mention here. SRAM has moved to a hydraulic lockout, called XLoc. It is lighter than, and arguably just as simple to install and maintain as its Pushloc cousin. Perhaps, most interesting is the new XX cassette. Like its Red counterpart, it is machined from a single piece of steel -- 10 hours of CNC-machining in each one!
7. Lighten your load.
SRAM chose to make their XX group as user-friendly as possible when they darn-near outfitted everything with T25 hardware. All but the crank and large chainring can be installed, adjusted, or otherwise with the same tool, making your on-trail tool kit that much lighter.
SRAM XX swept the podium at the 2009 MTB World Championships -- Schurter, Absalon, Vogel. It goes fast, on the trail and off the shelves. On both accounts we love it. If you haven’t tried it, beg, borrow, or buy an XX equipped bike to see for yourself how it feels. We’re sure that you’ll be impressed with the exacting feel of the shifting on both ends of the bike. Click the thumbnails below for more information.