This drag will reduce mpg and result in premature brake pad and rotor wear. Disc brakes are used primarily on front wheels but are also used on the rear of some vehicles. It is important to note that any brake system on a given vehicle operates in the proper front to rear sequence and that the left and right sides operate in unison to avoid undue premature lockup or lateral forces. Figure 1 Figure 1 illustrates a typical disc brake. Adjustment is automatic.
Several malfunctions are possible.
On the floating caliper, single piston design, the most likely culprits are a build-up of dirt, corrosion, or loss of the protective lubrication on the guide pins, sleeves or ways. These cause the caliper to not fully retract when the brake pedal is released. Figure 2a and 2b illustrate a typical single piston floating caliper disc brake at rest and when activated. Cross sectional view of single-piston caliper. Note that the hydraulic pressure pushes the piston outward and pulls the cylinder inward.