Vibration Diagnostics
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Vibration Diagnostics. Vibration Diagnostics. Vibration Diagnostics. Vibration Diagnostics. Why Wheel Balancing?. What is . Vibration?. Vibration?. Vibration?. Vibration?. In order to Diagnose a Vibration we must understand some... . Basic Principles. 1st cycle. 2nd cycle.

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Vibration Diagnostics

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Vibration diagnostics

Vibration Diagnostics

Vibration Diagnostics

Vibration Diagnostics

Vibration Diagnostics

Why Wheel Balancing?


Vibration diagnostics

What is

Vibration?

Vibration?

Vibration?

Vibration?


Vibration diagnostics

In order to Diagnose a Vibration we must understand some...

Basic Principles


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1st cycle

2nd cycle

What is a cycle?

1 second in time

2 cycles per second or 2 Hz


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Frequency

1 second in time

1st cycle

2nd cycle

Frequency is 2 CPS or 2 Hz


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1 second

Tire Imbalance

With a Frequency of 4 Hz

Imbalance

4 Revolutions = Frequency of 4 CPS/Hz


Vibration diagnostics

Amplitude of Force

1 second

6 Hz

Tire Imbalance

If the Frequency increases...

so does the amplitude of force

Imbalance


Vibration diagnostics

Reed Tachometer

can identify Frequency

500 250 100 25

Hz


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"Steering Wheel Shake"

Wobble

Shimmy

Waddle


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"Steering Wheel Shake"

5 to 20Hz


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What is Static Balance?

Static Balance is when the weight of the wheel and tire assembly is distributed equally around the axis of the wheel rotation.

If static Balance exists the wheel will have no tendency to rotate.

If rotated it rotates with Equal Force


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How do we Balance this Wheel?

Heavy Area Rotates to Bottom

.25 oz Imbalance


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Is this wheel in static balance?

.25 oz imbalance

.25 oz weight added


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If this wheel is in perfect balance at a

speed of 40 mph,

will it remain in balance at all speeds?

.25 oz imbalance

.25 oz weight added


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Yes,

the

is the word

“Perfectly”


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.86 lbs

.86 lbs

At 20 MPH

.25 ounces of imbalance generates

.86 pounds of force

Imbalance in Tire

Balance Weight Applied


Vibration diagnostics

10.5 lbs.

10.5 lbs.

At 70 MPH

.25 ounces of imbalance generates

10.5 pounds of force


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At 70 mph the force is 10.53 pounds

It's still in perfect balance!

10.53 lbs.

NOTE: Speed rated Tires Utilize a Nylon Over-lay to prevent tire distortion at high speeds.

10.53 lbs.


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Common Problems:

  • Round Off vs. Fine Mode

  • Mounting

  • Clean Mounting Surface

  • Excessive Runout

  • Tolerance stack up


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Consider this...

Most Computer Wheel Balancers Round off to the nearest .25 oz.

1 oz. Balance Weight

1.12 oz. Imbalance

Is this a Problem?


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1.12 ounces Imbalance

.25 Round Off = .12 Error

1 oz. Balance Weight

1.12 oz. Imbalance

Is this a Problem?


Vibration diagnostics

On most cars,

this Slight Imbalance would not be felt, however

"My Car Vibrates at 55 MPH"


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Why Does it Vibrate at

One Speed?

RESONANCE


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To Understand Resonance,

you must understand an objects

Natural Frequency

Mechanical Objects have there own

Natural Frequency


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1 second

Tire Imbalance

With a Frequency of 4 Hz

Imbalance

4 Revolutions = Frequency of 4 CPS/HZ


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Amplitude of Force

1 second

6 Hz

Tire and Wheel Frequency increases...

with Speed

Imbalance


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Suspension Natural Frequency

Range from 10 - 15 Hz/CPS

14 Hz

12 Hz


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Suspension Frequency

Tire & Wheel Frequency

Sum of Tire & Wheel

Beating - & - Phasing


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Vibration at One Speed

1st order harmonic

15

10

5

0 10 20 30 40 50 60


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"...But I balanced the tires in

the fine mode and...

... it still vibrates at 55 MPH"


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If a Tire and Wheel assembly is square,

can it be balanced to Zero?

Yes, balance only refers to force


Vibration diagnostics

Are Tires and Wheels

Perfectly Round?


Vibration diagnostics

Center Hole

-or-

Lug Circle...

can be off-center as much as .010”


Vibration diagnostics

95% of O.E.M wheels are Hub-centric

& *100% through 1 Ton

*(as of 1/1/00)

Mounting Error

Duplicate O.E.M. Mounting

Hub-centric

Are wheels centered by the center hole?

Are wheels centered by the lug nuts?

Lug-centric


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Mounting Error

Corvette Wheel

Hub-centric


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Tire High Spot

Wheel High Spot

Max assembly radial and lateral runout is .050” measured off the vehicle and .060” on the vehicle

Note: Rule of thumb for passenger cars and light trucks

Would this tire and wheel mismatch

cause a problem?


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One Revolution

Radial Runout


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15

10

5

0 10 20 30 40 50 60

Runout Problem

1st order harmonics


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Match Mounting

Mis-MatchedMatched


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Match Mounting


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Lateral Runout .045” Steel Wheel*

.030” Aluminum*

Radial Runout .040” Steel Wheel*

.030” Aluminum*

Wheel Runout Lateral and Radial

* Reference GM


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Radial Runout .040” Steel Wheel*

.030” Aluminum*

Wheel Runout Lateral and Radial

Measure runout at bead seat area

* Reference GM


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Lateral Runout .045” Steel Wheel*

.030” Aluminum*

Wheel Runout Lateral and Radial

Measure lateral runout at inside rim lip

* Reference GM


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Lateral Runout

.050” Off Vehicle*

.060” On Vehicle*

Radial Runout .050” Off Vehicle*

.060” On Vehicle*

Assembly Runout Lateral and Radial

* Reference GM


Vibration diagnostics

Radial Runout .050” Off Vehicle*

.060” On Vehicle*

Assembly Runout Lateral and Radial

Tape

* Reference GM


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Lateral Runout

.050” Off Vehicle*

.060” On Vehicle*

Assembly Runout Lateral and Radial

* Reference GM


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Dynamic Imbalance


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Dynamic Imbalance

1 oz. Imbalance


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During One Revolution


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Responder = Steering Wheel

"Shimmy"


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Dynamic Imbalance

Is normally not a problem

under 30MPH


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Dynamic Imbalance

Under 30MPH Excessive

Lateral Runout of Tire/Wheel

can cause

Low Speed “Waddle”


Vibration diagnostics

Look for Bulges

Bulges indicate weak areas and indention's are strong areas


Vibration diagnostics

Sidewall Stiffness

“Radial Force Variations”


Vibration diagnostics

Sidewall Stiffness

“Radial Force Variations”

Manufacturers Test for Radial Force Variations at the Factory

…and it is not a common problem


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Mounting Errors

.011” Can Results in 1oz. Dynamic Imbalance Error


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Mounting Errors

.011” Can Results in 1oz. Dynamic Imbalance Error


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Mounting Errors

Duplicate O.E.M. Mounting

Back Cone

-or-

Front Cone

Hub Centric

-or-

Lug Centric


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Mounting Errors

Check Cones for Damage or Wear

2.000”

2.001”


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Mounting Errors

On a 36 lb. Tire and Wheel, .006” cone wear can result in 1/2 ounce imbalance

2.000”

2.006”

Off center .006” creates more mass on one side


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...and don't forget about

Calibration

Eliminates Weight Chasing


Vibration diagnostics

On Behalf of

Thank You


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