Been riding the Sram XX for well over a hundred hours now, so I feel qualified to give my opinion on the super light top end XC race group. My 2011 S-works Stumpjumper hardtail came equipped with the group. Much like the Stumpy, the Sram group is meant for "race day only" use. Dark Horse has hooked me up royally when it comes to equipment, but believe it or not, I only have one Stumpy. I don't believe in jumping from one bike to another so I end up training on my race bike quite a bit. Hard on equipment, I've been called or as Gerry says it "You can break anything".
Rocking the 140...
I'll start by reviewing the XX disk brakes. My bike came with the super tricked out XX carbon levers that are integrated with the shifters. Very clean looking the way the brake lever and shifter pod mount together on the handlebar. The braking power is good considering I have a 140 rotor in the rear. No fade or chatter is detected at all. The XX rotors are still true, even after being crammed into a bike box and shipped across the country. I believe this is due to the fact this is a two piece design, much like the XTR rotor with a aluminum core. After leaving the bike alone for a few weeks I did notice the front lever was a little low, a quick adjustment on the little red knob under the lever brought that back even with the rear. This adjustment required no tools, but cannot be completed on the fly, due to the awkward position of the barrel adjuster under the lever.
The front derailleur and shifter pod work flawlessly from the first day I rode the bike. I've not even needed to adjust for cable stretch. One of the nicer features is being able to shift under load on the front chainring. Not full on sprint type load, but you don't need to back off much to complete the shift. The chainrings have held up well. Until recently (when I changed the cassette to a 12x28) I would mostly stay in the big ring (pretty much all the time), so the big is showing some wear. I'll change that soon.
I really liked the crispness of the Sram 9 speed stuff. Either the XO or the X9, both were borderline harsh, Snap! Shifts went off without a hitch. You knew you changed gears, even at a hundred and eighty beats per minute.
The XX seems to have adopted a lighter (Shimano type) touch. To shift to a harder gear is crisp enough, but the thumb paddle to go easier has a soft feel. Sometimes I, over (or under) shift, it's a little annoyance I thought I had gotten used to until I jumped back on my other bike with the XO group. To me, a night and day difference, maybe not a deal breaker, but worth a mention. The rear derailleur looks fragile but other then a cracked jockey pulley hasn't given me any issues... I do wish Sram would make a short cage option so I could shorten the chain a bit, avoiding annoying chain slap and getting it further off the ground to avoid rocks and sticks and stuff. Important in the Northeast.
The cassette is where this group really falls short for me. It's super light, it's super expensive, it's super fragile. It worked flawlessly for about a week, then it started to make noise (first sign of wear). I don't know anyone who has XX, and after a very short time hasn't replaced the cassette, most likely with a XT. Aluminum doesn't work on a cassette, it's just not a good place to save weight and at close to three hundred bucks, Naaaa.
I replaced my cassette with an 12x28 Ultegra, This gives me the most usable combinations for my fitness level, the gearing is tighter and the shifts are better. I actually use the inner ring now, but the low gear isn't gonna climb up the side of the empire state building. If your looking for that, get a triple. For me, if it's that steep, it's quicker to run.
This is a race bike, ya know...
So to sum it up....
Brakes: 4 out of 5
Front shifter and derailleur: 5 out of 5
Rear shifter and derailleur: 3 out of 5. note: I'd give XO a 5 and XTR a 3
Cassette, 11/36: Pffffft...Forget about it...
