Tires constantly evolve, applications vary and tire price points don’t always tell you the “life” you should expect from your tires. Just because you pay more for a tire doesn’t mean you will get higher mileage and more retreads.
When it comes to tires, the only way to determine what’s best for your application is to test them yourself by developing an on-going tire evaluation program and comparing the tires you currently run with a possible newcomer to your fleet.
Unlike a tire company that is testing products daily with dedicated technical professionals and sophisticated equipment, most fleets do not have the capability or bandwidth to conduct exhaustive testing. Yet, you can still do a valid evaluation within a fleet and get results that give you confidence in what to expect from selected tire brands.
To conduct an apples-to-apples comparison, run like-brand and like-model tractors or trucks, the same age, with the same specs. In addition, drivers comparable in skill level should run the trucks. Drivers can impact tire performance in subtle ways.
Routes and loads should be identical, or as similar as possible. Choose dedicated long-haul routes or similar types of service for a regional or local operation.
STEER TIRE EVALUATION
Outfit four trucks with your new evaluation steer tire and outfit another four with the steer tire you’re currently running for a head-to-head analysis. There are two reasons to run at least four vehicles:
1. To get a good average wear rate considering any variation in vehicles, routes or driver.
2. If you lose a tire due to a road hazard, you will still have three vehicles left running.
DRIVE TIRE EVALUATION
In this evaluation, you can use one vehicle to test two brands of tires. The only caveat is that their diameters need to be within 1/4” of each other. To put that into perspective, you can run one drive tire with 30/32nds of tread depth and have the competing drive tire within plus or minus 4/32nds of that figure.
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 percent faster than tires on the forward axle.
MAINTENANCE PRACTICES
Once tires are mounted, each vehicle should undergo a total vehicle alignment on the front and rear axles. It’s important for drivers to conduct proper pre- and post-trip inspections, including checking tire inflation.
Drivers also must keep their eyes and fingers on the tires to inspect for wear. A weekly fingertip diagnostic – simply running a hand over the tread – can detect signs of irregular wear.
If drivers detect early signs of irregular wear, your fleet can fix the underlying problem and continue with the evaluation. Be sure to keep a record of any wear issues and vehicle adjustments.
EVALUATION PERIODS
Evaluation units should be checked every 30,000 miles or every three months, whichever comes first (75,000 miles for steer tires). The first item to analyze is tread wear.
When checking the tire, you should have three points for gauging across the tread face – the outside, middle and inside of the tread. Again, a fingertip diagnostic should be conducted as well, and any signs of irregular wear reported.
If the irregular wear is found to be severe in the drive or trailer position, rotate the tires on the front rear axle in cross axle design. For example, LRI and O (Left Rear Inner and Outer) to RFI and O (Right Front Inner and Outer).
At about 75,000 miles, you should have solid wear data on your steer tires. Drive and trailer tires should give solid data at about 90,000 miles.
TREAD WEAR RATE
Now that you have data on how much tread is worn on your tires, how do you:
- Calculate your tread wear rate to project total miles to removal?
- Factor in casings and retreadings?
- Determine cost-per-mile?
Reuben DeBolt is the commercial technical services manager for Cooper Tire’s Roadmaster brand. Cooper Tire (us.coopertire.com) is a manufacturer of automobile, truck and motorcycle tires, inner tubes, vibration control systems and hose assemblies.
