How much do you have invested in your tires? If you operate three-axle mixers, it may total anywhere from $2500 for eight recap drive tires and two new steers, to almost $6000 for 10 new premium tires. If you pull a trailer delivering precast or hauling dozers, you can add $4000 or more. Add to that the effect that tires have on fuel economy, and tires can consume a significant portion of your fleet budget. You need to protect that investment.
Choose the right tread
When replacing tires, get the optimum tread for your needs. A shallow rib tread can reduce fuel use by at least 3% compared to a deep lug drive tire, but it won’t provide the traction you may need for on/off road operations. Work with your dealer to get the best balance of structure, compound, and tread pattern.
Watch for signs of wear. When tires show uneven wear, compare them to the American Trucking Associations’ Technology and Maintenance Council (TMC) Recommended Practice RP 219C - Radial Tire Wear Conditions and Causes. This guide analyzes causes of wear patterns and recommends corrective actions. Another useful document is RP 216C - Radial Tire Conditions Analysis Guide.
Stay in alignment
Wheels out of alignment can reduce fuel economy by 3% or more, and also dramatically shorten tire life, according to the TMC.
When properly aligned relative to the chassis and to each axle, tires run straight with minimal wear. When axles are not perpendicular to the chassis, the resulting thrust angles cause tires to scrub across the pavement. With just an 1/8-inch misalignment, a tire rolling 500 revolutions per mile will be dragged sideways more than 5 feet each mile. That scrub contributes to uneven wear. Even worse, it takes added energy to wear the tire, lowering mpg.
Align all wheels, including any trailers. This means all wheels and axles are in proper alignment, not just the tractor steer tires. Axles must be perpendicular to the vehicle center line to avoid wear from thrust forces set-up by wheels pointed to the side.
Steer tires should be checked for toe-in or toe-out, camber, and caster. Toe measures where the tires are pointing when seen from above. Caster is the angle of the steering assembly kingpin with the ground, as seen from the side. Camber measures if the tires are leaning inward or outward when seen from the front. Each of these affects tire wear, and uneven wear cuts tire life and costs money.
Keep tires properly inflated
Pressurized air is a structural part of the tire. In fact, air supports the entire truck. It’s as important as the steel belts, the radial cords, or the rubber itself. They are merely there to contain the air.
Air pressure keeps the tire from flexing too much. Flexing generates heat inside the tire, and excessive heat ruins tires. Without enough air, flexing can heat steel tire cords past the temperature at which rubber becomes liquid. When that happens, the tire can’t hold together. Chunks of tread start to fly off and tires delaminate.
Tire casings become damaged when running 20% or more under proper load/speed inflation pressure for any sustained period. Look at the next “gator tail” you see on the road. It probably will have steel cords coming out. That’s not a lost tread from a recap; it’s a section of a casing that let go due to excessive heat, caused directly by low air pressure.
Proper air pressure depends on load and speed. A given tire filled to 85 psi may be safe when running empty, but it could need 100 psi to carry a 9-yard load. Every tire manufacturer has load-speed tables for each of its tires (available from dealers).
Tire pressure monitoring systems alert drivers or mechanics at each wheel end or using dashboard monitors. Inflation systems help trailer tires maintain air pressure, even after minor damage.
Find a good balance
Much of the pavement pounding seen from loaded as well as empty trailers occurs because an imbalance wants to pull the tire off the pavement, then slam it back down as the tire rotates. Imbalance causes uneven wear.
Several devices help maintain balance with weights carried in viscous fluid, moving freely within a circular device bolted to or between wheels. Other products use granular material or fine glass beads inside the tires. The added masses automatically seek the proper position to balance the rotating assembly.
Match tire size
Keep tires in a dual set matched as closely for size as possible. One-quarter inch radius difference is the recommended maximum difference, but if you can, keep tire diameters matched to less than 1/8 inch. Since the two tires are bolted together at the wheels, they turn the same number of revolutions per mile. Because their diameters differ, they will travel different distances, resulting in scuffing and uneven wear.
At a 1/4-inch difference, the larger tire could carry 600 pounds more than the smaller one. It will also wear out faster. Both will wear unevenly. Note that even if perfectly matched by size, inflation differences will affect wear and load. With a 15 psi difference, the higher pressure tire will carry 500 pounds more than the other.
Establishing your own tire maintenance program is easy to do, and it will increase the use you get from your tires. If you maintain your tires well, you can have your own casings re-treaded. That way, you get a retread with a known history. A good casing, kept inflated, aligned, and balanced, should last two or three retread cycles, giving two or three more lives with new treads. Even if you don’t want to run retreads, a well maintained casing has significant trade-in value.