The carbon rims that came with my Epic are solid as can be, have been ridden over a lot of large rocks, and get airborne frequently. However, when building my SS MTB, I had to choose between alloy and CF. the weight difference was small, between the recommended rims, but the price difference was enormous. I went with the alloy rims, and I am very happy with them. Plus, in the end, the bike still came in at just over 20 lbs.