Ford Falcon. Manual — part 20

100-04-52

Noise, Vibration and Harshness

100-04-52

DIAGNOSIS AND TESTING (Continued)

Tyre Wear Patterns and Frequency Calculations

Tyre Wear Chart

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100-04-53

Noise, Vibration and Harshness

100-04-53

DIAGNOSIS AND TESTING (Continued)

Wheel and tyre NVH concerns are directly related to

vehicle speed and are not generally affected by

acceleration, coasting or decelerating. Also,

out-of-balance wheel and tyres can vibrate at more

than one speed. A vibration that is affected by the

engine rpm, or is eliminated by placing the

transmission in NEUTRAL is not related to the tyre

and wheel. As a general rule, tyre and wheel

vibrations felt in the steering wheel are related to the

front tyre and wheel assemblies. Vibrations felt in the

seat or floor are related to the rear tyre and wheel

assemblies. This can initially isolate a concern to the

front or rear.
Careful attention must be paid to the tyre and wheels.

There are several symptoms that can be caused by

damaged or worn tyre and wheels. Carry out a careful

visual inspection of the tyres and wheel assemblies.

Spin the tyres slowly and watch for signs of lateral or

radial runout. Refer to the tyre wear chart to

determine the tyre wear conditions and actions.
For a vibration concern, use the vehicle speed to

determine tyre/wheel frequency and rpm. Calculate

tyre and wheel rpm and frequency by carrying out and

following:

Measure the diameter of the tyre.
Record the speed at which the vibration occurs.
Obtain the corresponding tyre and wheel rpm and

frequency from the Tyre Speed and Frequency

Chart.

If the vehicle speed is not listed, divide the

vehicle speed at which the vibration occurs by

16 (km/h (10 mph). Multiply that number by

16 km/h (10 mph) tyre rpm listed for that tyre

diameter in the chart. Then divide that number

by 60. For example: a 40 mph vibration with

835 mm (33 in) tyres. 40

÷10 = 4. Multiply 4

by 105 = 420 rpm. Divide 420 rpm by 60

seconds = 7 Hz at 40mph.

Tyre Speed and Frequency Chart

Tyre Diameter

Tyre RPM/Hz

Tyre RPM/Hz

Tyre RPM/Hz

Tyre RPM/Hz

mm (inch)

@ 16 km/h (10

@ 80 km/h (50

@ 97 km/h (60

@ 113 km/h (70

mph)

mph)

mph)

mph)

483 (19)

182

910/15

1092/18

1274/21

508 (20)

173

865/14

1038/17

1211/20

533 (21)

165

825/14

990/16

1155/19

560 (22)

158

790/13

948/16

1106/18

585 (23)

151

755/13

906/15

1057/18

610 (24)

145

725/12

870/14

1015/17

635 (25)

139

695/12

834/14

973/16

660 (26)

134

670/11

804/13

938/16

685 (27)

129

645/11

774/13

903/15

710 (28)

124

620/10

744/12

868/14

735 (29)

119

595/10

714/12

833/14

760 (30)

115

575/10

690/11

805/13

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100-04-54

Noise, Vibration and Harshness

100-04-54

DIAGNOSIS AND TESTING (Continued)

Tyre Diameter

Tyre RPM/Hz

Tyre RPM/Hz

Tyre RPM/Hz

Tyre RPM/Hz

785 (31)

111

555/9

666/11

777/13

810 (32)

108

540/9

648/11

756/13

835 (33)

105

525/9

630/10

735/12

864 (34)

102

510/8

612/10

714/12

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100-04-55

Noise, Vibration and Harshness

100-04-55

GENERAL PROCEDURES

Using the match marks, mount the brake disc

Brake Disc Machining

on the hub.

12. Install the caliper.

CAUTION: Do not install brake discs that are

13. Install the tyre and wheel assembly.

less than the minimum thickness specified. Do

14. Test the system for normal operation.

not machine a brake disc below the minimum

thickness specification.

Powertrain/Drivetrain Mount

1. Check wheel bearing end-play and correct as

Neutralizing

necessary.

1. Raise and support the vehicle. For additional

2. Remove the tyre and wheel.

information, refer to Section 100-02.

NOTE: Begin at the front of the vehicle unless the

2. Loosen, but do not remove, the

vibration has been isolated to the rear.

powertrain/drivetrain mount fasteners.

3. Remove the brake caliper.

3. Lower the vehicle.

4. Inspect the brake linings. Install new brake linings

4. Move the vehicle in forward and reverse 0.6-1.2

if below specification. For additional information,

meters (2-4 ft).

refer to the appropriate brake section.

5. Measure and record the brake disc thickness.

CAUTION: Do not twist or strain the

Install a new brake disc if the thickness after

powertrain/drivetrain mounts.

machining will be at or below specification. The

5. Raise and support the vehicle.

specification is stamped on the brake disc. Do not

6. Tighten the powertrain/drivetrain mount fasteners.

machine a new brake disc.

7. Lower the vehicle.

6. For vehicles with a two-piece hub and brake disc

8. Test the system for normal operation.

assembly:

Match-mark before disassembly.

Exhaust System Neutralizing

Remove the brake disc.
Using a die grinder with a mild abrasive

WARNING: Exhaust gases contain carbon

(Scotch Brite® type), remove any rust or

monoxide, which is harmful to health and

corrosion from the hub and brake disc

potentially lethal. Repair exhaust system leaks

mounting surfaces.

immediately. Never operate the engine in an

Align the match-marks and reinstall the brake enclosed area. Failure to follow these instructions

disc on the hub.

may result in personal injury.

7. Using the special tool, machine the brake discs.

WARNING: Exhaust system components are

Follow the manufacturer’s instructions. After

hot. Failure to follow these instructions may result

machining, make sure the brake disc still meets

in personal injury.

the thickness specification.

NOTE: Neutralize the exhaust system to relieve strain

CAUTION: Do not use a bench lathe to

on mounts which can be sufficiently bound up to

machine brake discs.

transmit vibration as if grounded.

NOTE: The depth of cut must be between 0.10

1. Raise and support the vehicle. For additional

and 0.20 mm (0.004 and 0.008 inch). Lighter cuts

information, refer to Section 100-02.

will cause heat and wear. Heavier cuts will cause

poor brake disc surface finish.

CAUTION: Make sure the system is

warmed up to normal operating temperature,

8. Using a dial indicator, verify that the brake disc

as thermal expansion can be the cause of a

lateral runout is now within specification.

strain problem.

9. Remove the special tool hub adapter.

2. Loosen all exhaust hanger attachments and

10. Remove any remaining metal chips from the

reposition the hangers until they hang free and

machining operation.

straight.

11. For vehicles with a two-piece hub and brake disc

3. Loosen all exhaust flange joints.

assembly:

4. Place a stand to support the muffler parallel to the

Remove the brake disc from the hub.

vehicle frame with the muffler pipe bracket free of

Remove any remaining metal chips from hub

stress.

and brake disc mounting surfaces and from

5. Tighten the muffler connection.

the ABS sensor.
Apply a high temperature anti-seize lubricant

to the mounting surfaces.

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