Mazda RX-8 Workshop Manual page 1732

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2011 - RX-8 - Brakes
REAR BRAKE (DISC) INSPECTION
Description
Steering wheel vibrates in the rotation direction. This characteristic is most noticeable when applying brakes at a vehicle
speed of 100—140 km/h {62.2—86.9 mph} .
When applying the brakes, the vehicle body shakes back and forth. The seriousness of the shaking is not influenced by
vehicle speed.
When applying brakes, a pulsating force tries to push the brake pad back. The pulsation is transmitted to the brake
pedal.
Brake Judder Repair Hints
Due to an excessive runout (side-to-side wobble) of the disc plate, the thickness of the disc plate is uneven.
If the runout is more than 0.05 mm {0.002 in} at the position 10 mm {0.39 in} from the disc plate edge, uneven
wear occurs on the disc plate because the pad contacts the plate unevenly.
If the runout is less than 0.05 mm {0.002 in}, uneven wear does not occur.
The disc plate is deformed by heat.
Repeated panic braking may raise the temperature in some portions of disc plate by approximately 1,000 °C
{1,832 °F}. This results in a deformed disc plate.
Due to corrosion, the thickness and friction coefficient of disc plate change.
If a vehicle is parked in damp conditions for a long time, corrosion occurs on the friction surface of disc plate.
The thickness of corrosion is uneven and sometimes appears like a wave pattern, which changes the friction coefficient
and causes a reaction force.
Inspection and repair procedure