Getting the Right Rotation on Tires
Question: I have been getting some conflicting advice about tire rotation. The owner’s manual for my car suggests rotating the tires at different mileage levels and that I not crisscross the tires. But the local tire dealer wants me to rotate them every 4,000 miles and advises that the crisscross pattern is best. What do you suggest?
--H.S.
Answer: In almost every case, the radial tires sold in recent years can be rotated in an “X” pattern, or crisscrossed, as you say. Going back a decade, radial-tire manufacturers and auto makers recommended that tires be kept on the same side of the car when rotated, so that the tire did not change direction when rotated. The concern was that a change in direction would damage the cord body.
Radial-tire cord bodies have improved significantly since then, along with the general technology in radial tires. The “X” pattern rotation will even out wear on the tires better than any other pattern. One exception to rotating tires in the “X” pattern is when the rear tires are larger than the front tires, such as on the Chevrolet Corvette.
It is more important than ever to rotate tires, since forward wheel-drive cars put a lot more wear on the front tires. Without rotation, the front tires can wear out four times faster than the rear tires, because they carry more weight, provide greater braking and bear the load of acceleration.
Nonetheless, 4,000 miles is probably much more often than your tires will need to be rotated. Most car and tire manufacturers recommend longer rotation intervals. General Motors, for example, recommends a tire rotation at 15,000 miles and then another after 30,000 miles. And Toyota recommends a 15,000-mile interval on many of its cars.
Since radial tires can easily last more than 50,000 miles, a rotation every 15,000 miles will ensure that the tire is rotated several times over its service life.
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Q: I drive a 1989 Chevrolet Camaro Iroc Z-28, which has a 5.7-liter, fuel-injected engine that produces 245 horsepower. I have been told about a chip that can be added to the car’s computer that will increase the car’s performance. How does it work? Is it safe? Do you recommend it?
--D.I.K.
A: The chip is often referred to as a cheater chip, because it violates state and federal laws governing your car’s engine emissions. Thus, using the chip is illegal.
The chip is a so-called read-only memory computer chip, which has a set of instructions that controls the engine’s electronic fuel-injection system, among other things.
The chip improves engine performance by richening the fuel mixture--in other words supplying more gasoline to the engine. Generally, such chips only change the fuel mixture in a full throttle operating condition, which presumably is when you want the most performance.
As a result, it is often difficult for state smog certification tests to catch the cheater chips. The tests check idle and intermediate engine speeds, but not conditions under which the throttle would be wide open.
It is going to get tougher, however, to use cheater chips. Starting in 1993 in California and 1994 in the rest of the nation, the read-only memory chips that contain engine software will be soldered into the computer boards of engine controllers, rather than simply plugged in, according to a General Motors official.
That may thwart a lot of backyard mechanics who are tampering with their engine’s computers to get a little more performance at a cost of adding to air pollution.
