For this issue’s Maintenance Q & A, we invited Tim Miller from Goodyear Commercial Tire to address some of the most common technical questions he hears from fleet customers.
Q: Does deeper tread depth mean more miles to removal?
Miller: This sounds logical, but in reality too much tread depth will cause the tread lugs to compress and squirm which leads to premature removal because of fast and uneven wear. For every truck, application, and load bearing requirement, there is a specific tread design and depth that will provide optimum tire life and the lowest possible cost-per-mile. More is not always better.
Q: Does overinflating tires allow you to carry heavier loads without reducing speed?
Miller: No. Tires are designed to run at a specific inflation pressure. Overinflation reduces the tire’s “footprint” and places more weight on the centerline in the middle of the tire. Not only will this reduce your tire’s life, you compromise ride quality, stability, safety and traction because good traction is only possible when you use the tire’s full footprint.
Q: I’ve noticed that my left steer tire wears faster than my right steer tires. Is that unusual?
Miller: Typically, the left steer tire wears a little faster than the right steer tire. One reason is that the left front tire is connected directly to the steering box while the right front tire is connected to the steering box through the tie rod or tie bar. Since there will be some free play in the bushings at each end of the tie rod, the left side tire does the lion’s share of steering corrections as the truck moves down the highway—thus more treadwear.
Q: I know that wide-base tires reduce vehicle weight, but will they lower my overall cost-per-mile?
Miller: You’re correct in the fact that they can put your truck on a diet. From a weight-savings standpoint, converting from conventional tires on steel wheels to wide-base tires on aluminum rims can save over 1,000 pounds in total vehicle weight. Some of this weight-savings is from the aluminum wheels, which could also be used with conventional tires.
As for saving you money in cost-per-mile, that will take some analysis on your part. You’ll need to factor in weight, fuel economy, downtime, retreadability, and vehicle resale.
It is true that super singles may have less rolling resistance than many conventional tires but, with recent advances in fuel efficient tire designs, the difference can be nearly impossible to measure in real-world situations.
Replacement wide-base tire availability is also a major concern. Even in the most remote areas, it is relatively easy to find a conventional-sized tire. Some fleets concerned about this availability carry a spare, which negates the weight-savings benefit of the tire. In the event of a tire problem, the lack of availability and the inability to “limp in” on the other dual tire can create costly downtime.
Next, you’ll have to look at the life cycle of a wide base tire versus a dual tire. Typically, premium standard tires can be retreaded two to three times which drives down the overall CPM for that tire. Wide base tires, on the other hand, have not historically been as “retreadable.” This drives up your cost per mile since more new tires and fewer retreads can be used.
Finally, you must factor in the costs associated with conversion to wide-base tires, such as retrofitting axles to accommodate the wider tires. A “non-standard” axle width also could affect the value of your vehicle when you are ready to trade or sell.
Tim Miller has been with Goodyear for over 30 years. He spent 8 years as a tire design engineer before taking positions as a technical representative to original equipment customers (Freightliner, PACCAR, Volvo and Mack) and later as a technical rep to several large commercial tire customers. After 5 years in commercial tire sales (account executive to national account fleets), he returned for a second stint in the commercial tire marketing department.
Analyzing tire operating costs through software tools.
STTretread is now verified under the EPA SmartWay program