Rotor

I. Rotor Size

The larger the rotor diameter, the more brake power will be generated for a given input. Industry practices tend to specify 160mm rotors for XC application and 203mm rotors for DH applications. Larger rotors require less lever effort to generate a given amount of brake power, however inherently seem “grabby” and slightly more difficult to modulate.

II. Important Specifications

A. Hardness

Rotor hardness is a direct correlation to wear characteristics. Friction materials can be very aggressive and achieve high temperatures.

B. Run out

In order to ensure no free running drag, when mounted on a hub rotors must not have any “wobble” that would take up any pad clearance and drag on the pads.

C. Thickness Variation

Thickness variation must be kept to a minimum. Thickness differences in the rotor can cause pulsing in both the vehicle and the lever as thicker and thinner sections pass through the caliper pads.

III. Rub Area Design

The rub area of a rotor must be designed carefully. The rub area must provide adequate surface area to support the brake pads while braking. They must also have the proper cutouts to provide pad cleaning during braking. Finally, burnish, power, heat and noise issues are also considered when designing a rub area pattern.