[madmaxx]

4 to 6 oz of weight imbalance on the rim is alot. I am sure no rim or tire is perfect nor is the stiffness in the tiresidewall consistent. I would attempt to find a manufactures spec on rim imbalance. Here is a calculation I did for discount tire when they pissed me off one time.

"I visited Bay Area Blvd Discount Tire today (9/11/03). I noticed when the Tech balanced one of my tires, the balance machine indicated the tire to be .25 oz out of balance after he felt he was done balancing the tire. I notified the salesperson about the unbalance, the salesperson felt .25 oz was not enough to worry about. Being an engineer, I performed calculations on the force generated on the wheel assembly by the .25 oz of unbalance. As you can see by the calculations below at 65 mph, the .25 oz unbalance causes a force equal to 4.075 lbs. to act on the wheel/car 14 times per second!! This is what causes vibration issues and customer dissatisfaction. The other three tires were balanced to zero, how much longer would have it taken to balance the one wheel correctly, 30 seconds. Imagine being hit in the face by 4.075 lbs, 14 times per second, do you think you would feel it? Please share with your Techs so they can understand the importance of balancing a tire properly. As usual the customer pays the price with time and money. One thing I did gain from this experience is a story I can tell everyone I know about the ability of Bay Area Blvd Discount Tire.

Tire Imbalance Calculation

Tire Size P215/65R15
Rim Size 15”
Section Height of Tire = .65*215mm=139.75mm = 5.50 inches
Overall Diameter of Tire / Wheel assembly = 26 inches
Circumference of Tire = 3.14 (26) = 81.64 inches = 6.80 feet
RPM @ 65 MPH = 6600 ft/min * 1 rev / 6.80 ft = 970 RPM = 16.17 RPS
Force of unbalance in lbs = 1.77*W*R*(RPM/1000)^2
W= Weight in ounces
R= Radius in inches
Force of unbalance in lbs due to .25 oz unbalance at 65 MPH
F(lbs) = 1.77*.25oz*13*(970/1000)^2 = 4.075 lbs
According to the calculation at 75 MPH, 14 time per second 4.075lbs is acting on the tire!! The force goes up exponentially with speed, at 75 mph the force is 5.41 lbs, 16.17 times a second.

P.S.
I did contact the assistance service manager, James, he was very polite and agreed the service should have been performed differently. He suggested I bring the car back to have the issue resolved. Since my hourly rate is $75/hour, the better alternative for me is to take it elsewhere, where it can be done right the first time and minimize my time loss." [/i]