Brakes - Roughness/Pulsation/Steering Wheel Shake

Article No.
92-4-3

02/12/92

BRAKES - ROUGHNESS, PULSATION OR STEERING WHEEL SHAKE - ANTI-LOCK (4 WHEEL DISC) AND BASE BRAKE (REAR DRUMS) SYSTEMS

FORD:
1989-92 THUNDERBIRD

LINCOLN-MERCURY:
1989-92 COUGAR

ISSUE:
Brake roughness, pulsation and steering; wheel shake, may occur because of uneven rotor wear. Two major causes of uneven rotor wear are...

^ Abrasive brake pads (semi-metallic material)

^ Hub or rotor high and low spots (improper orientation during assembly)

Usually these vehicles appear to be corrected by just installing new pads and rotors. However, they can repeat the condition after some time in service unless proper attention is given to...

^ Front Brake Pads

^ Hub/Rotor "Stacked" Runout

^ Tire Wear And Balance

^ Rear Brake Rotors Or Rear Brake Drums

ACTION:
Check the front brake pads, hub/rotor "stacked" runout, tire wear/balance and rear rotors/drums. Refer to the following procedure for service details.

FRONT BRAKE PADS

1. Replace the front brake pads with ONLY the new asbestos pads (F1SZ-2001-A).

CAUTION:
USING METALLIC FRONT BRAKE PADS (FOSZ-2001-A) WILL CAUSE UNEVEN ROTOR WEAR.

2. Refer to the 1992 Thunderbird/Cougar Service Manual, Section 06-03, for service details.

HUB/ROTOR "STACKED" RUNOUT CHECK

If the assembled system (new rotor installed on hub) indicates more than .002" (.051 mm) total runout (TIR), it will cause excessive thickness variation in the rotor as mileage accumulates by wearing the high spots off the rotor. Excessive thickness variation in the rotor causes brake pulsation and steering wheel shake.

High system runout (TIR) is caused by...

^ Rust/contamination trapped between the hub and rotor mounting surface

^ Rotor or hub (high and low spots) not being properly oriented during assembly

1. Clean the hub area that will contact the new rotor. Remove rust build-up and debris.

2. Install a new rotor (FOSZ-1L104-A for 1989/90 vehicles and F1SZ-1125-A for 1991/92 vehicles) on the hub.

a. Secure it with at least four (4) lug nuts.

b. Tighten the four (4) lug nuts to 10 Lb-Ft (13 N.m) for testing.





3. Using a dial indicator (TOOL-4201-C) or equivalent, determine the total runout of the system, Figure 1. The total system (rotor and hub) runout must not exceed .002" (.051 mm).

4. If the runout exceeds .002" (.051 mm), remove the rotor and rotate it clockwise until the next hole lines up with the stud.

a. Secure the rotor in the new position, re-indexed, as in Step 2.

b. Repeat the checking and rotation (re-indexing) process until the system measures .002" (.051 mm) or less total runout.

5. If .002" (.051 mm) or less runout can not be reached, replace the hub. Repeat Steps 2 through 4 when the new hub is installed.

NOTE:
BASED ON EXPERIENCE, WE RECOMMEND THAT NEW BRAKE ROTORS SHOULD NOT BE MACHINED. NEW OEM REPLACEMENT ROTORS ARE WELL WITHIN THE RUN OUT AND THICKNESS VARIATION SPECIFICATIONS.

TIRE WEAR AND BALANCE

Tire wear and balance can cause or add to a brake roughness concern. After the brake system is serviced, the tire wear and/or balance could cause enough input to be perceived as a brake roughness condition.

1. Place the best tires on the front.

2. High speed balance all the tires.

REAR BRAKE ROTORS/DRUMS

Rear brake rotors/drums can contribute to the complaint and feel as if the front brake concern was not fully corrected. In some cases vibration is found in the rear rotors/drums from an out of specification condition.

1. Use the parking brake moderately instead of the service brakes from 55 mph (89 km/h) to 45 mph (72 km/h) to determine if the rear brakes are contributing to the concern.

2. If the roughness is present, service the rear rotors/drums as necessary.

PART NUMBER PART NAME CLASS

F1SZ-2001-A Brake Shoe Lining BG
FOSZ-1L104-A Rotor (1989/90 Vehicles) BG
F1SZ-1128-A Rotor (1991/92 Vehicles) B

SUPERSEDES: 90-22-5, 91-24-4

WARRANTY STATUS: Eligible Under Basic Warranty Coverage For 1989-91 Models, Bumper To Bumper For 1992 Models

OPERATION DESCRIPTION TIME

920403A Replace front pads 0.9 Hr.

920403B Clean hub surface and 0.4 Hr.
check rotor runout

920403C High speed balance tires 1.0 Hr.

920403D Replace hub - one side 0.6 Hr.

920403E Replace hubs - both sides 0.9 Hr.

DEALER CODING
CONDITION
BASIC PART NO. CODE
1125 13

OASIS CODES: 301000, 302000, 703000