Has anyone built one up yet?
One of my riding partners has one.
Lefty carbon + new XTR crank + Dura ace DID.
He's one of the Shimano disributers here.
No problem there.
2x10 vs 3x10 comparison on Rockstar
When I originally built my Rockstar, I put an X0 3x10 drivetrain on it. I rode it this way for about 6 weeks. A few days ago, I decided to pull my XX 2x10 drivetrain off my 26er (Titus X) and put it on my Rockstar. I've put a little over 60 miles on it in a few days and here's my report:
The weight dropped from 26 lbs 3 oz to 26 lbs 2 oz when I put the XX crankset on it. So, no big weight savings. I used Sheldon Brown's gear ratio calculator to compute how many gears I lost by going with the XX setup. I lost 4 gears -- 2 at the bottom end and 2 at the top end of the spectrum. My normal after work ride takes me from my house, down a paved hill to the trailhead at the Greenbelt. The 2 high-end gears were missed on this downhill stretch as I ran out of harder gears while going downhill. But, this isn't really a big deal since it's unlikely that this would be a problem going down a dirt hill.
I went to a notoriously steep section of trail that I've struggled with in the past. I was never able to ride this steep, dirt, and rocky hill on my Titus X with a 3x9 or with the XX drivetrain. The first time I tried it on the Rockstar, I made it. So, now I do hill repeats (4 at a time) on this hill for training. I have been completing this hill on 100% of my attempts on the Rockstar with the 3x10 setup. I was able to ride the hill on the Rockstar with XX setup about 50% of the time. It's a lot more work without those 2 lower gears. When doing hill repeats, I'm able to complete the hill the first 2 times I ride it, but the 3rd and 4th tries are failures. I'm just too wiped out from the previous attempts. With training, I'm sure I'll be able to climb it all 4 times in a row, but it's much easier with the extra gears. For all my other riding, the XX setup is great.
My conclusion... I'm going to switch back to the 3x10 because I get the extra low gears without much of a weight penalty. However, if you're not riding stupid steep hills, the 2x10 is great. I love the 2x10 setup on my 26" bike.