It's a well-known fact that passenger-car and light-truck tires will deliver higher mileage if they are rotated on a regular basis. Everything from irregular treadwear patterns to accelerated shoulder wear can be minimized, or even eliminated, when the direction of rotation and position on the vehicle are regularly changed. Even with an increasing number of directional tires that cannot be moved from side to side without demounting the tire from the rim, the benefits of rotation are realized by consumers on a daily basis.
Very few commercial truck fleets rotate drive tires on tandem axle power units, probably because it's not a simple or easy process. As a former technician, I can recall a few customers who rotated drive tires, but most replaced the four tires across the rear axle first and when the front axle wore out, the rears would get moved to the front drive axle and the new tires would be installed in their place. Some didn't even bother and just replaced drive tires four at a time regardless of position.
Advances in suspension, drivetrain and anti-lock braking systems (ABS) on commercial trucks may force fleets to rethink their position on rotating tires. And if that isn't enough to bring about change, the introduction of automatic traction control (ATC), electronic braking systems (EBS), and electronic stability control (ESC) could be the types of technology that eliminate all discussion.
These technologies are all engineered to give the driver an improved margin of safety when road conditions are at their worst. Everything from stopping distance to rollover protection is improved with these technologies, but all are dependent on the tires. Besides the obvious importance of sufficient tread depth, a long-standing Rubber Manufacturers Assn. (RMA) guideline may become more important than ever.
In its “Care and Service of Truck Tires” publication, RMA includes a provision that warns technicians of the damage that can occur to drivetrains and differentials when the tire diameter between the two axles of a tandem axle tractor differs by more than 0.25 inches. I wonder how many repair bills they paid before they placed that warning on page 33?
I've talked about this in training classes for the last ten years and have yet to meet a tire dealer who was aware of the guideline. But I've also heard from numerous former students who have avoided paying for differential damage because they warned the customer that the drive tires should have been rotated or replaced as a set of eight.
Tire rotation on tandem axle power units is not an inexpensive or risk-free proposition. From a time factor alone, tire dealers cannot possibly provide the service at no charge and there's always the chance of a loose wheel or “wheel-off” when wheel change intervals are increased. Proper torque, installation procedures and technician training will be the primary factors that determine success or failure.
Even though there's no documented evidence that ABS, ATC, EBS or ESC are dependent on tire rotation, it makes sense that a major difference in tire diameter between axles may have a negative impact. Fleets that pay the premium for this technology should contact their truck manufacturer for recommendations on tire rotation and tire diameter difference on drive axles, Those who don't can still benefit from longer tire mileage.
