2018 Peterbilt 579: Tire Size, Pressure, & Specs

Quick answer

• OEM Tire Size: 295/75R22.5 is the most common steer and drive tire size. Low-profile 295/60R22.5 or 445/50R22.5 super singles are also frequently used.
• Recommended Cold Tire Pressure: Steer tires typically run 110-120 psi, while drive tires are often set to 85-100 psi, depending on load.
• Bolt Pattern: 10x285.75mm (10-on-11.25") is the standard for hub-piloted wheels.
• Wheel Size: 22.5" x 8.25" for standard duals or 22.5" x 14" for super singles.
• Load Index/Speed Rating: Typically 144/141L or similar, indicating a max load of 6175 lbs (single) / 5675 lbs (dual) at a top speed of 75 mph.
• Spare Tire Size: Most semi-trucks do not carry a spare tire due to size and weight. Tire services are used instead.
• TPMS Frequency: Most modern Peterbilts utilize a 433 MHz TPMS system.

Tire Sizes by Configuration

The 2018 Peterbilt 579 is highly customizable from the factory. While the 295/75R22.5 is the workhorse, other configurations are specified based on the intended application, such as fuel efficiency or heavy haul routes.

Recommended Replacement Tires

Choosing the right tire depends heavily on your routes, loads, and budget. Here are three popular options for a 2018 Peterbilt 579:

• $$$ - Michelin X-Line Energy Z (Steer) / X-Line Energy D (Drive): Considered a top-tier option, these tires are designed for maximum fuel efficiency and long tread life on highway routes. They offer excellent performance but come at a premium price.
• $$ - Bridgestone R284 Ecopia (Steer) / M710 Ecopia (Drive): A very popular and competitive choice that balances fuel economy, durability, and cost. It's a reliable all-around performer for long-haul and regional applications.
• $ - Goodyear Endurance LHD (Drive): A cost-effective option known for its long-lasting tread and durability in high-scrub applications. While not always the most fuel-efficient, it provides a low cost-per-mile, making it a budget-friendly choice.

When to Inflate to Max Load PSI

On a heavy-duty truck like the Peterbilt 579, tire pressure is critical and directly related to the load being carried. The "max load psi" listed on the tire's sidewall should only be used when the axle is loaded to its maximum legal limit.

Always inflate tires based on the axle load. Over-inflating tires for a light load will result in a harsh ride, premature center tread wear, and a reduced contact patch, which can decrease braking effectiveness. Conversely, under-inflation for a heavy load is extremely dangerous, leading to excessive heat buildup, potential blowouts, and rapid shoulder wear.

It is best practice to use a load and inflation table provided by the tire manufacturer to determine the correct PSI for your specific axle weights. Check pressures when the tires are cold.

Lug Nut Torque & Pattern

• Torque Spec: 450–500 ft-lbs (610–678 Nm)
• Socket Size: 33mm for most hub-piloted wheels.
• Pattern: For a 10-lug wheel, tighten in a star or crisscross pattern to ensure the wheel is seated evenly against the hub. Torque lug nuts in stages, for example, to 100 ft-lbs first, then to 250 ft-lbs, and finally to the final torque spec. It is highly recommended to re-torque all lug nuts after the first 50-100 miles of driving after a wheel has been installed.

Common Tire Issues for this Vehicle

• Irregular Steer Tire Wear: The 579, like many modern aerodynamic trucks, can be sensitive to alignment. Misalignment is a primary cause of rapid or uneven steer tire wear, often appearing as feathering or cupping. Regular alignments are crucial to maximizing tire life.
• River Wear / Channel Wear on Trailer Tires: While not specific to the tractor itself, this is a common issue seen in the application. It appears as wavy wear across the tread face and is often caused by a combination of trailer suspension issues, tire balance, and non-optimized tread designs for free-rolling axles.
• Mismatched PSI in Drive Duals: Ensuring both tires in a dual assembly are at the exact same pressure is critical. If one tire has lower pressure, it will have a slightly smaller circumference, causing it to be "dragged" by the properly inflated tire. This leads to rapid, irregular wear on the underinflated tire.

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