Adding tire rotation to your maintenance routine probably sounds like a nuisance. But even when alignment is kept up to snuff, tires do wear unevenly. Add to this the tendency for parts to wear and get out of alignment before you take action, and tire rotation begins to make more sense.
Some experts believe rotation can even out wear and put off the date when tires need to be removed for retreading or replacement because of worn tread. Other tire makers aren’t so quick to recommend it.
“You should rotate only based on actual problems,” says Walt Weller, vice president sales at CMA, maker of Double Coin tires. However, he has seen cases in which some long-haul fleets run steer tires in the drive position for the first 15,000 to 25,000 miles because steers are “prone to irregular wear” in the steer position, but less so after being slightly worn in a drive position. From a wear point of view, this may make sense, but, he says, “Some say the trouble is not worth it. You have to consider the cost of rotating those tires.”
Yokohama’s Pat Keating, senior technical engineer, points out that trailer tires get less benefit from rotation. “Whether the additional mileage is added in a cost-effective way depends on the particulars” of the operation.
“If it is application-specific,” says Ron Gilbert, director of commercial products at Toyo Tire USA, “then tire rotation may be warranted to prolong tire life. Other than this, tire rotation on commercial vehicles causes increased labor cost for little, if any, return on your investment.”
So is it cost-effective to rotate in your application? Consider these points.
“Tires wear at different rates,” says Guy Walenga, Bridgestone/Firestone’s director of engineering. “A good time to rotate is when there’s 3⁄32-5⁄32 difference in wear” between the tire positions. Due to how torque is applied on the front and rear drive axles of a three-axle tractor, “the forward axle doesn’t wear quite as fast because of the way the vehicle pivots,” he adds. “The forward axle doesn’t scrub as much. Something similar happens on the trailer.”
How the load is situated plays a role in uneven wear, too. “Each drive axle should carry half the load,” Walenga says, “but if the fifth wheel is forward or back, the load will not be 100 percent even.”
He adds that one consequence of this uneven wear can be a difference between the rotating speed of the front and rear drive axles. “There is a 3 percent window, and, after that, you get ‘gear fight’ or rotation of the inter-axle differential gears as you cruise down the road,” he says. Rotating your drive tires could conceivably help your inter-axle differential to live longer.
Also, he explains, the left-front steer tire wears faster on a tandem drive tractor. That’s because the steering action is transmitted to the left-front tire directly, while the force travels through more linkage parts and so takes a little more of a rotation of the steering wheel to get to the right-front tire.
CMA’s Weller agrees this wear pattern is common, but he believes it’s often because of bearing problems.
Irregular wear caused by mechanical problems is the other reason to rotate. Correcting the mechanical problem before the tires are rotated, though, is key. Doug Jones, customer engineering support manager for Michelin Americas, puts it this way: “Rotation is not the answer to solving an axle misalignment issue or other mechanical issue that may be impacting the way the vehicle’s tires wear. Irregular wear and/or disproportionate wear rates are good indicators of vehicle and/or mechanical issues.”
“Steer tires should be rotated from side to side,” says Jones. “Drive tires can be rotated from the front axle to rear axle, side to side across the axle, or crisscrossed.