Is it offset by the ability to make SUBSTANTIALLY lighter rims as they no longer need to be structured to withstand the heat from friction/brake pad wear?
I think that’s wishful thinking…and apparently Wayne Stetina of Shimano is of the same opinion:
Shimano: When you take the braking surface off the rim on a mountain bike, you can reduce material there and weight. I don’t believe we can do that on a road bike. If you eliminate the brake surface on a road bike and reduce material, I think you’re going to make it too fragile. It would be unable to maintain its stability.
Weight is more critical. The brake system itself isn’t so much the problem as redesigning the frames for the different torsional loads and redesigning the front wheel to accommodate for the asymmetrical dish. Radial lacing designs won’t work, I think the wheel manufacturers have a bigger challenge than the brakes manufacturers.
http://www.bikerumor.com/2012/02/14/road-bike-disc-brakes-are-coming-but-will-they-work/