They have 12 mm Q-Factor (similar to Profile Cranks). Moment Cranks had 10 mm Q-Factor. The additional 2 mm is needed to clear the brake caliper. There is 20 mm clearance between the rotor and cranks. If it appears that they have more, it’s because the back face is cut away more than Moment Cranks.
In practice, they are effectively the same - you don’t notice any difference when riding.
Attached are assembly instructions for the disk cranks, where you can see further details on how it all fits together.
A major amount of work was put into the tight tolerances required to efficiently fit the caliper between the spokes and the inside face of the crank. A lot of detail work was also put into the rotor-mount (spider), for aesthetics (e.g. to blend the rotor into the crank) and to maintain strength. I wanted to keep it low profile so that the cranks are a worthy upgrade irrespective of whether you care about disk brakes.
As far as the external rotor goes, it works incredibly well. Early in testing, I was concerned about hitting my ankle on it, but even when “trying” to hit the rotor, I can’t do it. It just works. One of those rare times when you get to have both light weight and strength at the same time.
The aesthetics of the double hole look good in real life. I think that a lot of riders may like the new 110/137 size.
KHU Spirit Cranks Disc Brake Installation Instructions.06-2012.EN.8.5x11.pdf (175 KB)