Tires can be an endless headache for fleet managers trying to determine which brands and types perform best in their applications. The best way to make that determination is to conduct a tire test to see how a prospective tire stacks up compared to other makes and models.
Tires constantly evolve, applications vary, and tire price points don’t always tell you the life you should expect from them, says Phil Mosier, manager of commercial tire development for Cooper Tire. Just because you pay more for a tire doesn’t mean it’s the best tire for your operation, he adds, noting that fleets should strive to find the tires that give them the lowest cost of ownership. Cooper looks at four pillars to determine a fleet’s true cost: initial tire cost, mileage to removal, fuel efficiency, and retreadability (or casing value).
“The best way to determine what’s best for your operation is to test tires yourself by developing an on going tire evaluation program and comparing the tires you currently run with a possible newcomer to your fleet,” Mosier says. “Granted, it’s not easy. You have to track tires and take tread measurements; you have to maintain excellent maintenance practices to ensure inflation levels are correct and that alignments stay true. And, to get results that will give you accurate information, you need to run the test tires for long-haul operations to 50 to 60% of their wearable tread depth.”
Peggy Fisher, an experienced fleet manager who is now president of Tire Stamp, says in the real world, tire tests are always a challenge due to the many variables. These can include vehicle models, routes, loads, weather, and drivers, to name a few. And each and every one can affect the outcome of a tire test to one degree or another.
“Running a test is more than just throwing a few tires on a few trucks and seeing what happens,” Fisher cautions. “Tire testing requires that you establish and follow a testing protocol as closely as possible in real-world operations.”
To begin with, Fisher recommends fleets start with a reasonably large group of tires, with a goal of having 30 test tires in service at the end of the test. “You should plan on losing 10% to 15% of the tires during the test and plan accordingly,” Fisher says. “You can use smaller sample sizes, but your results will not be as accurate as 30 tires to examine at the end of the test.”
Moiser says that, obviously, the more trucks and tires the better. But, at bare minimum, he recommends if you’re evaluating steer tires, run four trucks equipped with them. This will give you good average wear rate data — plus if you lose a tire due to a road hazard, you will still have three vehicles left in the test.
“If you’re evaluating drive tires, you can test two brands of tires on one vehicle,” Moiser says. “The only caveat is that their diameters need to be within ¼-inch of each other. With this evaluation, you can run two trucks with eight wheel positions. The key is doing an X-pattern (or cross-axle) on the two rear axles. However, don’t run the tires identically on the two trucks. The right rear outer tire historically wears faster than any other drive position tire due to a higher percentage of right-hand turns, which can cause scrubbing. Be sure to have brand X in that position on one evaluation truck, and brand Y on the next truck. Also, note that tires on the trailing axle typically wear about 20% faster than tires on the forward axle.”
For best results, Fisher suggests using broken-in trucks with at least 15,000 to 30,000 miles on them. She also recommends keeping the vehicle loads and weights on trucks in the test as similar as possible. Along the same lines, she says fleets should conduct alignments on all test trucks and replace any worn steering or suspension components prior to beginning the test.
“I’d also screen out any drivers known for having unusual or erratic driving habits,” she adds. “You also need to be consistent with the use of aluminum or steel wheels and their respective sizes.”
Retreads are totally in bounds for tire tests too, Fisher adds, although she recommends that all casings be from the same manufacturer, and any retreading should have been done within a one-year time frame.
Making sure everyone in the fleet knows a tire test is being conducted is critical as well, Fisher stresses. To do this, she says it is important to uniquely ID all test tires using radio tags, bar codes or labels. Going one step further, she also recommends stenciling “test tire” in bold letters on the tires so people can’t miss it. “Make sure your drivers are alerted to the fact that there is a tire test under way, too,” she adds.
Additionally, Fisher recommends:
- Using standard inflation pressures and checking them on all tires at least once a month.
- Continuing with a normal tire rotation program — but do not begin tire rotations if this is not a normal maintenance procedure for your fleet.
- Check vehicle alignments several times during the course of the tire test.
- Check tires for nails and remove any found, even if they haven’t punctured through to the tire’s pressure chamber.
- Take tread depth measurements at regular intervals — every 30,000 miles and at scheduled maintenance intervals. Take these measurements consistently at the same spot in a major tread groove. Use valve stems as a reference point for taking tread measurements.
- Keep data on tires removed from test due to damage. Note the reason for removal, tread depth, condition, and mileage. Label the removed tire with vehicle number, mileage, and wheel position, and photograph the tire for future reference.
Once the test is under way, Fisher says preliminary findings, including indications of the tires’ performance, can start to be made when the test tires are at least 50% worn down. And she says to remember that tire wear rates vary according to axle and wheel positions — with left-hand steer tires typically wearing faster than right-hand steer tires, as Mosier notes.
Once you’ve done those things, time and accurate data collection are your main considerations as the test proceeds. But once it is complete, you’ll have enough baseline information to begin making smarter tire purchases.