Brake Pulsation

Brake pulsation is caused by brake rotor thickness variation. Brake rotor thickness variation causes the piston in the brake caliper, when applied, to "pump" in and out of the caliper housing. The "pumping" effect is transmiffed hydraulically to the brake pedal. Brake pulsation concerns may result from two basic conditions:

^ Thickness Variation Caused by Lateral Run Out (LRO) - LRO on a brake corner assembly is virtually undetectable unless measured. If the brake corner is assembled with excessive LRO (greater than 0.050 mm (0.002 in), thickness variation will develop over time and miles. Excessive LRO will cause the brake pads to wear the brake rotors unevenly, which causes rotor thickness variation. Pulsation that is the result of excessive Lateral Run Out usually develops in 4,800-16,000 km (3,000-10,000 mi). LRO can be induced when uneven torque is applied to wheel nuts (lug nuts). Improper wheel tightening after tire rotation, spare tire usage, brake inspection, etc. can be the cause of pulsation.

4. Back off a full turn and position the cutting bits all the way inboard in preparation to refinish the full rotor surface. Advance both tool cutters to the zero setting plus just enough to clean up the entire rotor surface.

5. After completing the refinish, sand both sides of the rotor for approximately one minute per side using a sanding block and 130-150 grit sandpaper to obtain a non-directional finish.

Important:
Only remove the necessary amount of material from each side of the rotor and note that equal amounts of material do not have to be removed from both sides on any brake system using a floating caliper.

Important:
In many of these instances, such a minimal amount of material is removed from the rotor that customer satisfaction is not a concern for future brake services. This procedure is intended to "Clean-up" the rotor surface and should be conveyed to the customer as such - not as "cut" "refinish" or "machine", which tends to be terms understood as a substantial reduction of rotor material/life. If the brake lathe equipment being used is not capable of removing minor amounts of material while holding tolerances, further lathe maintenance, repair, updates or equipment replacement may be necessary.