Brakes - Steering Wheel Vibration/Pedal Pulsation

Classification:
BR00-002

Reference:
ITB00-009

Date:
February 10, 2000

TITLE:
AMMCO ON-CAR BRAKE LATHE OPERATING PROCEDURE

APPLIED VEHICLES:
All Infiniti vehicles with disc brakes

SERVICE INFORMATION
If an Infiniti vehicle exhibits steering wheel vibration and brake pedal pulsation when braking, it may be brake judder. Brake judder is created by excessive thickness variation of the brake rotors. In most cases the thickness variation is a result of excessive brake rotor run-out. While brake judder is usually associated with the front brake rotors, the rear brake rotors may cause it too.

The most effective way to eliminate brake judder and excessive rotor run out is to turn the brake rotors using the Ammco on-car brake lathe. This required special tool will minimize the assembled brake rotor run-out more than the conventional off-car turning/installing on hub process. Please note the following points when using the on-car brake lathe:

^ 5GPrevent metal shavings from contacting or collecting on the ABS speed sensors. Remove any shavings that stick to the ABS speed sensor's magnet. It is best to clean the ABS sensor with the rotor removed.

^ 5GMark the exact location of the rotor (on the axle hub) before removing the rotor (see Figure 2 on page 2).

^ 5GDo not tighten the wheel lug nuts with an air impact driver. Uneven or high torque applied to the lugs may distort the brake rotor and hub, resulting in increased rotor run-out and excessive rotor thickness variation as the rotor wears.

^ 5GIf new rotors are required, install them on the hub in different positions (index) to achieve the lowest run-out reading (equal to or less than 0.0012", 0.03 mm), using a dial indicator. See Figure 11.

SERVICE PROCEDURE

Figure 1:

1. Measure the rotor thickness at 10mm in from the outside diameter of the rotor to ensure the rotors can be turned. (See Figure 1).

A. If the rotor thickness is below specification, the rotor cannot be turned, but must be replaced. When installing new rotors, install them on the hub in different positions (index) to achieve the lowest run-out reading (equal to or less than 0.0012", 0.03 mm).

B. If the rotor thickness is within specification, the rotor can be turned. Proceed with step 2 below.

Warning: Do not cut below the minimum rotor thickness specification. Replace the rotor if the run-out cannot be eliminated without exceeding the minimum rotor thickness specification.

2. Remove the brake caliper assembly.

CAUTION: Do not allow the brake caliper assembly to hang from the brake hose. Use a piece of wire to hang the caliper from the front coil spring.

Figure 2:

3. Put an alignment mark on the rotor and the axle to ensure the rotor remains in its original position (see Figure 2).

4. Assemble the legs on the lug adapter according to the lug pattern of the vehicle being worked on (see Figure 3). Then tighten the bolts that secure the legs to the adapter, making sure the legs are flat against the adapter and freely rotate.

Figure 3:

5. Orient all legs to the full outside position, against the stop pin (see Figure 3).

Figure 4:

6. Install the lug adapter on the brake rotor (see Figure 4). Tighten all lug nuts to 40 ft/lb.

NOTE: Ensure that all lug nuts are installed on the lug studs - including the lug studs not used for the lug adapter legs.

NOTE: Make sure the lug adapter is centered on the brake rotor (see Figure 4).

7. Install the brake lathe on the vehicle as follows:

A. Loosen the bolts holding the adjustable mounting brackets on the lathe and slide the brackets in or out to align with the holes in the caliper mounting bracket on the vehicle.

NOTE: If the mounting brackets on the lathe do not adjust in or out far enough to reach the caliper mounting holes, the brackets may be switched end-to-end or switched end-to-end and turned 90 degrees to match the caliper mounting holes.

Figure 5:

B. Mount the lathe against the inboard side of the caliper mounting bracket using the appropriate adapter mounting bolts, sleeves and spacers to achieve adequate clearance between the lathe and the brake rotor (see Figure 5).

Figure 6:

NOTE: Use the appropriate adapter mounting bolts and sleeves to ensure the lathe is firmly mounted and that NO movement (play) exists between the caliper mounting bracket and the lathe. Also, make sure there is sufficient clearance between the adapter mounting bolts and the brake rotor (see Figure 6).

8. Install the silencer band on the outside diameter of the brake rotor to dampen vibrations during cutting.

Figure 7:

9. Position the cutting bits about 10 mm in from the outer edge of the rotor surface (see Figure 7).

NOTE: Make sure the cutting bits are sharp and in good condition. Also, cutting bits should not be used more than ten times as they wear out.

10. Turn the (blue) depth-of-cut knob clockwise to advance the outboard cutter until it lightly contacts the rotor surface. Hold the knob still while rotating the micrometer dial to zero (see Figure 7). Then, turn the depth-of-cut knob 1 notch counterclockwise.

11. Turn the (red) depth-of-cut knob clockwise to advance the inboard cutter until it lightly contacts the rotor surface. Hold the knob still while rotating the micrometer dial to zero (see Figure 7). Then, turn the depth-of-cut knob 1 notch counterclockwise.

NOTE: Once you have zeroed a micrometer dial, never use the dial to advance or withdraw a cutting bit; the dial may slip, losing the zero position. Only use the depth-of-cut knob to advance or withdraw the cutting bit.

Figure 8:

12. Advance the carriage with the hand wheel until the outboard cutting bit reaches the inside edge of the rotor surface (see Figure 8). Then, advance the carriage movement hand wheel an additional one-third turn.

13. Turn the depth-of-cut knobs individually to set each cutting bit to the desired depth of cut. Each cut may be between 0.002" and 0.004" (0.05 mm and 0.10 mm), but the final cut must be made at 0.001 " (0.025 mm).

Figure 9:

14. Tighten the cutter locking knobs (see Figure 9).

Figure 10:

15. Connect the rotor driving unit to the lug adapter (see Figure 10).

NOTE: Before using the rotor driving unit, ensure that all lug nuts are installed on the lug studs - including the lug studs not used for the lug adapter. Tighten the lug nuts to 40 ft-lb.

NOTE: Make sure the rotor driving unit cable is exactly level with the center of the lug adapter (see Figure 10).

16. Activate the rotor driving unit.

17. Tighten the engagement knob in the center of the carriage movement hand wheel (see Figure 9) to start the cutting process. When the cutting bits clear the outer edge of the rotor, loosen the engagement knob to stop the carriage movement.

18. If part of the brake surface was not cut, leave the cutters in the locked position and move the carriage until the cutters are at the inside edge of the braking surface, then repeat steps 12, 13, 14, 16 and 17.

19. Turn the rotors with a finish-cut of 0.001", (0.025 mm).

NOTE: The brake lathe cutting bits must be replaced after they have been used 10 times.

Figure 11:

20. Use a dial indicator to ensure the rotor run-out is within specification (see Figure 11). Rotor run-out should not exceed 0.0012" (0.03 mm).

Figure 12:

21. Turn the rotors and hand finish the newly turned rotor surface with a non-directional swirl pattern using #500 grit aluminum oxide sandpaper. This improves the rotor surface finish and helps to further reduce noise (see Figure 12).

NOTE: Use a small flat block of wood between the sandpaper and your fingers to ensure a flat, smooth surface finish (see Figure 12).