Why do I need a floating rotor?

In order to determine which rotor will be right for your riding situation, it’s important to understand the various types currently available on the market. Motorcycle rotors are typically offered in three different mechanical designs: one-piece, two-piece, and fully floating.

One-piece rotors, like the ones that come OE on a Harley-Davidson, are just a solid shape, usually stamped out of stainless steel. Solid rotors of this variety are easily mass-produced. As a result, they’re generally the cheapest on the market. However, they’re limited in stopping performance and service life.

The two-piece rotor has a carrier that is separate from the friction ring. The two-piece rotor is essentially the same as a solid, one-piece rotor because the carrier is attached to the friction ring. The two are bolted together with hardware or a rivet and high-pressure cone washer, in a manner that offers zero movement between the two pieces. While the two piece rotor offers no mechanical advantage over a one-piece rotor, it does allow the manufacturer to offer a wider variety of style options.

Fully floating rotors have a carrier that is completely independent of the friction ring. The carrier is attached to the friction ring via buttons with low pressure spring washers and c-clips or a helical retaining clip as found in our Lug Drive rotors. On a fully floating rotor, all three of these pieces will move independently of each other with little effort. Float, or movement, is about .0020”.

Floating rotors offer superior mechanical advantage over solid rotor types because when the friction ring gets hot, it grows in diameter. Keep in mind that the outer diameter of the rotor gets much hotter than the inner diameter. This variance in temperature causes a variance in material expansion. The fully floating rotor design compensates for this variance by allowing room (.0020”) for the friction ring to grow independently of the carrier, dramatically increasing rotor stability, stopping performance, and service life, while also diminishing the possibility of warpage under the most extreme of conditions.

Rotors are manufactured of various materials. Most rotors are made of stainless steel, either 410 or 420 grade. Stainless steel is an inherently stable, heavy, and hard material, so it takes a good polish. Some high-performance rotors are made of ductile iron. Ductile iron has the highest coefficient of friction of any rotor surface. But, iron rusts and is not as stable as steel. Recent advances in metal-matrix composite and the processes associated with manufacturing from this material have made composite materials a newcomer to the rotor industry.

Metal matrix composite (MMC) is a mixture of aluminum and ceramic. MMC is a most interesting material with the measurable ability to shed heat and weight, as well as noise. These advances in material options available for the manufacture of motorcycle rotors allows Lyndall Racing Brakes to manufacture an 11-1/2” fully floating rotor that weighs 1-1/2 pounds, has a coefficient of friction consistent with an iron rotor (but never rusts).