Interesting, I've always heard 20%, sometimes 25%. I don't know if it matters, but I'm running a vigilante single disk. I dyno'd just under 400 hp at the wheels, like 396 I think. With a 20% loss factor, thats roughly 500 at the flywheel. I'm just trying to maximize my combo, but don't want to make over 600 at the flywheel. Thanks.