2017 Peterbilt 579 Wheel Alignment Specifications

Quick reference

Adjustability

On a 2017 Peterbilt 579, the front axle alignment is the primary focus, as this is where most adjustments are made and where most alignment-related issues originate. The rear axles are typically non-adjustable, but their alignment is still measured to ensure they are tracking straight ahead in relation to the front axle and chassis centerline.

• Front Camber: Camber is not factory-adjustable on most Peterbilt 579s. If the camber is out of specification, it typically indicates a bent or worn component, such as a wheel bearing, kingpin, or axle beam. Correction often requires replacing the worn or damaged parts. In some cases, aftermarket offset kingpins or axle shims can be used to bring camber back into spec, but this should be done with caution.
• Front Caster: Caster is adjustable on the Peterbilt 579. This adjustment is made using shims on the front axle. Adding or removing these shims tilts the axle forward or backward, which changes the caster angle. Proper caster is critical for straight-line stability and steering wheel return.
• Front Toe: Toe-in is the most common and critical adjustment on any heavy-duty truck. On the 579, it is adjusted by changing the length of the tie rod that connects the two steering knuckles. Loosening the clamps on the tie rod and rotating it will either push the front of the tires out or pull them in.
• Rear Axle Alignment: The rear tandem axles are not adjustable for camber or toe. Their alignment is set at the factory. If a rear axle is out of alignment, it is usually due to worn suspension components (like torque arm bushings) or damage to the axle housing or frame. The primary concern with rear axles is ensuring they are parallel to each other and perpendicular to the chassis, which results in a zero thrust angle.

Recommended adjustment hardware

For most adjustments on a 2017 Peterbilt 579, the factory hardware is sufficient. Caster is adjusted with OEM shims, and toe is adjusted via the tie rod assembly.

When non-adjustable angles like camber are out of specification due to slight bends or tolerance stack-up, the industry often turns to specialized aftermarket components. For a Peterbilt, this might include:

• Offset Kingpins: These can provide a small amount of camber and/or caster change to correct for minor deviations in the axle or knuckles.
• Axle Shims: For severe camber issues, specialty shops can install shims between the axle and the spring pack, although this is a less common and more involved repair.

For rear axle alignment issues, the solution is almost always the replacement of worn bushings, particularly the torque arm and equalizer bushings that locate the axles.

Symptoms of bad alignment

Misalignment on a heavy-duty truck will quickly lead to premature tire wear and can cause handling problems. The cost of a single steer tire makes keeping the alignment in check a top priority.

• Feathered Tire Wear: This pattern, where the tire tread blocks are worn high on one side and low on the other, is a classic sign of incorrect toe settings. The tire is essentially being dragged sideways as it rolls forward.
• One-Sided Shoulder Wear: If the inside or outside shoulder of the tire is wearing down significantly faster than the rest of the tread, this points to an incorrect camber angle. Positive camber wears the outside shoulder, while negative camber wears the inside shoulder.
• Steering Wheel Pull: If the driver has to constantly hold the steering wheel off-center to maintain a straight path, this can be caused by unequal caster from side to side or a significant thrust angle from the rear axles pushing the truck to one side.
• Driver Fatigue: A vehicle that requires constant steering corrections is tiring to drive over a long haul. Proper alignment results in a truck that tracks straight with minimal input.

When to align

A wheel alignment should be considered a regular maintenance item, not just a repair. An alignment check is recommended:

• After purchasing new steer tires: To protect your investment, an alignment is crucial to ensure the new tires wear evenly from the start.
• After any suspension or steering component replacement: Any time a part that affects the geometry of the suspension is replaced (e.g., kingpins, tie rod ends, spring bushings, steering gear), the alignment must be checked and adjusted.
• After a significant impact: Hitting a large pothole, curb, or road debris at speed can be enough to knock the alignment out of specification.
• When uneven tire wear is noticed: If you see any of the wear patterns described above, have the alignment checked immediately to prevent further damage to the tires.

Typical alignment cost

The cost for a three-axle alignment on a Class 8 truck like the Peterbilt 579 can vary based on location and the shop's labor rate, but it generally ranges from $250 to $500. This is significantly more than a passenger car alignment due to the size of the vehicle, the specialized equipment required, and the time it takes to perform the adjustments correctly. While it may seem expensive, this cost is easily justified by extending the life of a set of steer tires, which can cost upwards of $1,000.

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