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Wheel Balance Theory

Balance - UnbalanceWhat does it mean?

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Balance....by definition

The stability resulting from the equalization of opposing forces.

Equal Force

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Types of imbalance...

StaticSingle Plane

DynamicTwo Plane

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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 you Static 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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...and, if this wheel is in static balance?

If this wheel is in perfect balance at a speed of 40 mph, will it remain in balance at all

speeds?

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The answer: yes, BUT... can you Prove it?

At 20 mph .25 oz of imbalance generates .86 pounds of force

.86 lbs

.86 lbs

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At 70 mph the force is 10.53 pounds

It's still in perfect balance!

10.53 lbs

10.53NOTE: Speed rated Tires Utilize a Nylon Over-lay to prevent tire distortion at high speeds.

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One common problem:

Improper use of equipmentMounting Method

Clean Mounting Surface

Calibration

Careless Weight Placement

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Consider this...

1.12 oz. Imbalance

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

1 oz. Balance Weight

Is this a Problem?

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Is this “rounding off..” a Problem?

On most cars, this slight imbalance would NOT be felt.

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BUT, some Customers......

Complain about a Vibration at one Speed!

Why?

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...vibration at one speed!

is why a Vibration may occur at one particular Speed!

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Natural Frequency

Mechanical Objects have there own Natural Frequency

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Tire & Wheel "Natural Frequency"

4 Revolutions = Frequency of 4 CPS/HZ

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Tire & Wheel Frequency Change with Speed

Vehicle Speed Increasing

Tire imbalance frequency increasing

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Suspension Natural Frequency

14 Hz

12 Hz

Range from 10 - 15 Hz/CPS

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Beating - & - Phasing

Suspension Frequency

Tire & Wheel Frequency

Sum of the two above

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The point at which it is felt...

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10

5

0 10 20 30 40 50 60

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...and, the complaint...

"...but, I balanced the tires in the FINE/NON-ROUND-OFF mode and...

...it still vibrates at 55 M.P.H.

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What's the Problem?

Mounting Error

Are wheels centered by the center hole?Hub-centric

Are wheels centered by the lug nuts... or...Lug-centric

Duplicate O.E.M. Mounting

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...also, Consider this

Are Tires and Wheels Perfectly Round?Tire High Spot

Wheel High Spot

Would this Mismatch cause a problem?

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15

10

5

0 10 20 30 40 50 60

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Match Mounting

Mis-Matched Matched

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Dynamic / 2-Plane

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Dynamic Imbalance

1 oz. Imbalance

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During one revolution