Wheel Balance Theory

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Wheel Balance Theory
Balance - Unbalance What 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...
Static Single Plane Dynamic Two 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
NOTE Speed rated Tires Utilize a Nylon Over-lay
to prevent tire distortion at high speeds.
10.53
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One common problem

• Improper use of equipment
• Mounting Method
• Clean Mounting Surface
• Calibration
• Careless Weight Placement

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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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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
Tire imbalance frequency increasing
Vehicle Speed Increasing
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Suspension Natural Frequency
Range from 10 - 15 Hz/CPS
14 Hz
12 Hz
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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...
15 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