A "Because it's important to be clear about what's being compared, we'll compare Buell's ZTL to a conventional double-disc system. ZTL has less unsprung weight, and the reduction in wheel weight is mostly near the hub. Some heat will be transferred to the rim and tire through the fasteners, which might be a negative factor in racing applications. However, the rotating mass/inertia of the large-diameter ZTL disc and its fasteners are a negative factor. You'd have to do the math to get an exact rotational comparison with two discs, but that one big disc certainly isn't a large improvement.