INSPECTION

NOTE: Mitsubishi does not provide resurfacing specifications. Any disc which is gouged, scored, worn or warped should be replaced.

Run-out

Before measuring the run-out on the front discs, confirm that the front wheel bearing play is within specification.

1. Raise and safely support the vehicle on jackstands. If only the front is supported, set the parking brake and block the rear wheels.
2. Remove the wheel.
3. Remove the brake caliper from its mount and suspend it out of the way by a piece of wire. Don't disconnect the fluid hose and don't allow the caliper to hang by the hose. Remove the brake pads with all the clips, springs, shims, etc.
4. Inspect the disc surface for grooves, cracks and rust. Clean the disc thoroughly and remove all rust.
5. Mount a dial indicator with a magnetic or universal base somewhere on the vehicle so that the tip of the indicator contacts the rotor about 0.20 in. (5mm) from the outer edge.
6. Zero the dial indicator. Turn the rotor one full revolution and observe the total indicated run-out. Refer to the Brake Specifications chart in this section for the specifications for your vehicle.
7. If the run-out exceeds the maximum allowed, the rotor needs replacing.

Thickness

The thickness of the rotor or disc partially determines its ability to withstand heat and provide adequate stopping force. Every rotor has a minimum thickness established by the manufacturer. This minimum measurement must NOT be exceeded under any condition. A rotor which is too thin may crack under braking; if this occurs the wheel can lock instantly, resulting in loss of control and a possible collision.

If any part of the rotor measures below minimum, the disc must be replaced. Since the allowable wear from brand new to minimum is only 0.04–0.06 in. (1.0–1.5mm), resurfacing is not recommended.

Thickness and thickness variation can be measured with a micrometer capable of reading to 0.00010 in. (0.0025mm). All measurements must be made at the same distance in from the edge of the rotor. Measure at four equally spaced points around the disc and record each measurement. Compare the measurements to the minimum specifications in the chart. A rotor varying by more than 0.0010 in. (0.025mm) can cause pedal vibration and/or front end vibration during stops. A rotor not meeting thickness requirements, or with varying thicknesses, must be replaced.

Condition

A new rotor will have a smooth, even surface which rapidly changes with use. It is not uncommon for a rotor to develop very fine concentric scores (like the grooves on a record) due to dust and grit being trapped by the brake pads. This slight irregularity is normal, but as the grooves deepen, wear and noise increase and stopping may be affected. As a general rule, any groove deep enough to snag a fingernail during inspection is cause for rotor replacement.

Any sign of blue spots, discoloration, heavy rusting or outright gouging require replacement. If you are checking the disc on the truck (such as during pad replacement or tire rotation) remember to turn the disc and check both the inner and outer faces completely. A small mirror and a bright light can be very helpful in seeing the inner face of the rotor. If anything looks questionable or requires consideration, choose the safer alternative and replace the rotor. The front brakes are a critical system and must be maintained at 100% efficiency.

Any time a rotor is replaced, the pads should also be replaced so that the surfaces mate properly. Since brake pads should be replaced in sets (both front or rear wheels), consider replacing both rotors instead of just one. The restored feel and accurate stopping make the extra investment well worthwhile.