Brakes - Front Brake Judder: Overview
NO.: DATE TSB-91-35-004DATE: April, 1991
MODEL: 1990 - 91 Eclipse, 1989 - 91 Galant
SUBJECT:
FRONT BRAKE JUDDER
Note:
TSB # 9135004, dated 4/91 has been updated by TSB # 9135004, dated 6/91.
PURPOSE
If you encounter a "judder" condition when the brakes are applied, use the revised rotor checking and truing procedures described in this bulletin in conjunction with front brake pad kits to resolve this condition.
VEHICLES AFFECTED
1990 and 1991 Eclipse models and 1989-90 Galant models.
WARRANTY INFORMATION
Standard warranty procedures and coverage apply.
CHECKING PROCEDURE
Before replacing brake pads, it is essential that the rotors be parallel and true within specifications given in this bulletin. The procedure is as follows:
1. Check and correct rotor thickness variance (parallelism).
2. Check and correct rotor run-out (wobble).
3. Replace the front brake pads wfth new ones from the kit.
WHEN USING ON-CAR ROTOR MACHINING EQUIPMENT
If on-car rotor-turning equipment is used, parallelism and run-out can usually be brought within specifications in a single operation. Be sure the lug nuts are properly torqued before turning the rotor!
WHEN USING AN OFF-CAR BRAKE LATHE
If the rotor is removed from the car to machine it, then the procedure becomes more complex:
1. Machine the rotor to bring the surfaces parallel within specifications; then mount the rotor on the vehicle's hub and measure run-out.
2. If run-old is not within specs, index the rotor (change its phase on the hub) until run-out is within specs. This part of the procedure is described in more detail later.
These repair steps outlined in this bulletin are shown graphically in the diagram.
Figure 1:
1. Thickness variance (Parallelism):
Maximum thickness variance must be less than 0.015 mm (0.0006 in.)
Measure rotor thickness at 8 or more points. See Figure 1. Record each thickness reading. Compare the largest to the smallest. The difference (largest - smallest) must be less than 0.015 mm (0.0006 in).
Resurface the rotor to equalize the thickness.
Minimum thickness is 22.4 mm (0.882 in).
NOTE:
Use on-car equipment if possible.
Figure 2:
2. Run-out:
Run-out is measured laterally with a dial indicator with the rotor secured to its hub with the lug nuts and evenly torqued to specifications. See Figure 2.
Maximum rotor run-out is 0.07 mm (0.0027 in).
Figure 3:
3. Indexing (changing phase):
If run-out exceeds specifications after truing the rotor, then try indexing, or changing the phase of the rotor on its studs. (A chalk mark on the rotor and on a stud will remind you where you started. See Figure 3).
NOTE:
It is not possible to phase rotors on vehicles equipped with Anti-Lock Brakes.
Figure 4:
The rotor can be indexed to multiple positions. See Figure 4.
NOTE:
The wheel nuts must be installed and torqued to specs each time the rotor is indexed!
Figure 5:
After each indexing of the rotor on its hub, measure the run-out with a dial indicator (Figure 5). If run-out is within specifications, replace the brake pads as described below. If run-out exceeds specifications in all positions, replace the hub before replacing the brake pads.
HUB REPLACEMENT
Replace the hub as described in the Service Manual - but only if rotor run-out exceeds specifications.
Figure 6:
PARTS INFORMATION
Modified pad kits:
FRONT DISC PAD AND SHIM SET (Figure 6)
APPLICATION PART NUMBER
(FRONT ONLY)
1990 PRODUCTION UP TO VIN MB895168
# 22700 (TO MAY 1989)
ECLIPSE 1990 PRODUCTION FROM VIN MB895072
# 22701 (FROM MAY 1989)
ALL WHEEL DRIVE (AWD) MB895072
1989 -1990 MB895168
GALANT 1991 MB895072
ALL WHEEL DRIVE (AWD) MB895072
Figure 7:
TYPICAL BRAKE SHIM INSTALLATION INSTRUCTIONS
Refer to Figure 7.
1. Cut a corner off the supplied brake grease package, apply a thin coating of grease to the back surface of the pad.
WARNING:
Do not allow any brake grease to contact the friction material. If the friction material becomes contaminated with the brake grease, discard the pad.
2. Place the slotted shim onto the back surface of the brake pad. Apply additional brake grease to the slotted shim.
NOTE:
The inboard pad slotted shim "snaps" onto the pad. The outboard pad slotted shim is placed on the pad with the "tabs" facing away from the pad.
3. "Snap" the solid shim onto the pad.
4. Carefully wipe away any excess grease which may have squeezed out.