Firestone Shop’s Rotation Pattern Elicits Concern of SUV Owner

Thursday marks a year since the mounting toll of deadly accidents linked to Firestone tires and Ford Explorer sport-utility vehicles triggered a massive recall. The issue is no longer on the front pages of newspapers, but tire safety is something that should never be dismissed or forgotten.

In this column, I’ll deal with two important questions about tire maintenance raised by Your Wheels readers.

Question: My local Firestone dealer mailed me a coupon for a free tire rotation and inspection. The tires on my four-wheel-drive 1998 Ford Explorer Sport with 16-inch wheels (not covered by the current Firestone recall) were due for a rotation.

My question concerns the rotation pattern. I marked the tires before leaving home. The left-front tire was merely swapped with the left-rear and the right-front swapped with the right-rear. Was this correct? The owner’s manual suggests the X pattern. When I called the Firestone store, I was told that the pattern is dependent on the mileage. --S.N., Los Angeles

Answer: Yikes! The rotation was not done according to either the specification in the owner’s manual or Firestone’s recommended pattern. Your dealer’s failure to follow Firestone’s own recommendation is troubling, particularly given the history of Firestone tires on Ford Explorer sport-utility vehicles, a combination that has been linked to scores of deaths across the country.

Rotation is crucial to ensuring that your tires wear evenly and to maximizing tread life. Ignoring rotation can accelerate abnormal wear, such as balding edges and cupping. Unfortunately, there’s little agreement on rotation frequency. Firestone recommends every 5,000 miles, but Ford specs as reported by the Mitchell On-Demand repair information service call for a rotation every 10,000 miles under normal conditions.

On four-wheel-drive vehicles such as your Explorer, Firestone recommends a modified X pattern, in which you move the left-rear tire to the left-front position and the left-front tire to the right-rear. The right-rear tire is moved to the right-front spot and the right-front tire is moved to the left-rear.

That recommendation is fairly standard across the auto industry for four-wheel-drive vehicles. Other rotation patterns are based on whether the car or truck in question is front-wheel drive or rear-wheel drive, and whether the tires on the front and rear are of the same or different specifications.

In any case, it’s important to get the right rotation pattern for your vehicle. You should take your SUV back to the Firestone store and request that the service be done correctly. You also should call Firestone customer service at (800) 367-3872. Ford’s customer service line is (800) 392-3673.

Q: Is there some standard accepted by the tire industry relating to balancing tires? What does “balance” mean?

I doubt that it means what I was told recently when I bought two new tires. Concerned because there was only one small weight on one wheel, I took them to be checked by another garage. It found one wheel had a weight on the wrong side.

When I returned to the tire dealer, I was told that its standard for balancing was that if the customer didn’t feel a vibration, the dealer considered the tire balanced. What is the correct standard?

--R.B., Long Beach

A: It is entirely possible that the wheel needed only a single weight to be properly balanced. But it is ludicrous that the dealer’s standard for a properly balanced tire is the vehicle occupants’ sensitivity to vibration.

An out-of-balance tire does produce vibration, which may or may not be felt by passengers, depending on the vehicle, the sensitivity of the passengers and the location of the out-of-balance tire, said Mike Smith, Goodyear Tire & Rubber’s manager for product service. Out-of-balance tires in the rear often produce vibration that cannot be felt inside the vehicle, for example.

Driving comfort is just one potential problem with out-of-balance tires. In the long run, imbalance can accelerate wear on suspension parts and create wear patterns on tires that can lead to premature balding.

Almost all balancing these days is done on a dynamic balancing machine that spins the tire and wheel to sense torque forces. It automatically lets the mechanic know where on the rim to place a weight to balance the wheel, as the mechanic manually rotates the tire after the machine stops spinning.

Inherently well-balanced wheels and tires may require few weights. Cast-alloy wheels, for example, are generally better balanced out of the factory than stamped-steel wheels.

In general, a wheel out of balance by half an ounce is noticeable. But a good balancing should cut that out-of-balance condition to well under a quarter-ounce. Wheels can require as much as 3 ounces of added weight per side to achieve proper balance.

Once you have new tires balanced, they generally should remain so. But uneven wear, such as cupping, can put tires out of balance; sometimes a weight will fall off the rim. In such cases, it may be necessary to re-balance the tires, particularly after a rotation.

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Ralph Vartabedian cannot answer mail personally but responds in this column to automotive questions of general interest. Please do not telephone. Write to Your Wheels, Business Section, Los Angeles Times, 202 W. 1st St., Los Angeles, CA 90012. E-mail: ralph.vartabedian@latimes.com.