Back to Overview

The Brake's Fade Resisting Properties

Fade in conventional disc brakes results from two basic causes: 

(1) The brake pads overheat, reducing their coefficient of friction which decreases braking ability, and 
(2) excessive heat in the brake pads is transferred via the hydraulic pistons to the brake fluid, which boils and produces bubbles in the brake lines.

The CirCal Disc Brake resists these fade inducing causes by: 

(1) Distributing in-pad heat over a greater area and conducting heat both away from and through the brake pads into the brake body structure to enable more efficient heat dissipation, and 
(2) isolating the hydraulic cylinder from the brake pads so that direct heat is not transferred to the brake fluid.

1. The Heat Dissipation Benefits of Full Circle (Annular) Pads:

All brakes get hot. Excessive heat reduces the coefficient of friction between the pad and rotor and leads to ‘brake fade’.  Kinetic energy generated by a moving vehicle (a product of its mass and speed) is converted to heat during braking. This kinetic energy, and the resulting heat, will be the same for any brake or brake configuration in a particular application. How a brake dissipates the heat to prevent overheating the pads is crucial; some brake designs are more efficient heat dissipaters than others.

Typically, the rotor acts as a heat sink into which the majority of heat is absorbed, and it is cooled by air passing around it and, where applicable, being forced through its internal venting by means of aerodynamically shaped vanes. The mass and design of the rotor is therefore important to its function as a heat sink. Contrary to popular belief, cross-drilled holes do not aid cooling directly since very little air moves through them, and they may diminish a rotor's capacity as a heat sink and exacerbate pad overheating.  It is likely that a larger proportion of heat is dissipated via a rotor's internal venting since the internal venting has a larger surface area than the rotor's external sides.

Full circle brake pads have a much larger friction surface area than conventional pads (between 7 to 10 times larger, depending on the pad geometry), which allow faster heat transfer from the friction surface into both the rotor and the pads. The faster heat is transferred into the rotor the less it will heat the pads and minimize brake fade. Heat not absorbed by the rotor is absorbed by the brake pads. 

Full circle pad wear is proportionally less than conventional pads since wear is distributed over a larger surface area. This permits a substantially thinner pad to be used while maintaining an equivalent pad usage life. Thinner pads create a shorter thermal path to the pad backing plates. Pad backing plates made from a high thermal conductivity material such as aluminum will further enhance the heat transfer to the brake body structure. The brake body itself is used to dissipate heat more efficiently to the adjacent air stream. The optimization of heat dissipation through the brake pads, in addition to conventional dissipation via the rotor vanes, minimizes fade caused by excessive brake pad temperature.

2. Isolation of Brake Fluid from the Heat Source:

The CirCal brake’s hydraulic cylinder* is typically located behind the pressure plate and has no direct contact with the heat generating pad/rotor interface. This isolation of the hydraulic cylinder from the heat source prevents excessive heat reaching the brake fluid.