ASE A4 Suspension and Steering

B. Front tires move straight back; rear tires move to the opposite front position.

The 'front-to-back, cross-to-front' pattern for FWD vehicles means the front tires go straight to the rear, and the rear tires move forward to the opposite side.

D. Perform a dynamic balance on all four wheel assemblies.

A high-frequency vibration and shimmy in the steering wheel at specific speeds, combined with irregular tire wear, strongly suggests an imbalance in the front wheel assemblies. Dynamic balancing is the direct solution for this.

B. Bent steering knuckle

A sharp pull to one side after an impact, combined with excessive positive camber on the opposite wheel, strongly suggests a bent component that directly controls camber. A bent steering knuckle is a common result of severe impact (like a pothole) that would cause such a change in camber.

D. Re-balance the tire and wheel assembly.

Any time a tire is dismounted, repaired, or new components (like a plug/patch) are added, the weight distribution changes. Re-balancing the assembly is crucial to prevent vibrations and ensure proper handling.

A. Unbalanced front wheels

Vibrations felt through the steering wheel, especially at specific speed ranges, are most commonly attributed to an imbalance in the front wheels. Rear wheel imbalances often manifest as a vibration through the seat or floor.

C. Right front wheel bearing

When turning left, the vehicle's weight shifts to the right side, increasing the load on the right wheel bearings. A grinding noise that intensifies under load (turning left) indicates a faulty bearing on the loaded side, which in this case is the right front.

B. Left front wheel bearing

When a vehicle turns right, the weight shifts to the left side, increasing the load on the left wheel bearings. If a bearing is faulty, this increased load will make the grinding noise louder. Conversely, turning left shifts weight away from the left bearing, making the noise quieter.

C. Improper wheel lug nut torque.

Improper or uneven lug nut torque is a very common cause of warped brake rotors. Uneven clamping force from the lug nuts can distort the rotor, leading to thickness variations or lateral runout that causes pulsation during braking.

A. Excessive negative camber

Excessive negative camber causes the top of the wheel to tilt inward, placing more weight and wear on the inner edge of the tire. Since both front tires show this, it points to a camber issue rather than a pull from toe or a single-side issue.

D. Replace the tire.

Industry standards (e.g., RMA guidelines) specify that tire repairs are only permissible in the tread area within certain limits, typically excluding punctures too close to the sidewall. A puncture 1 inch from the sidewall is usually considered too close, making replacement the safest option.

C. The wheel speed sensor tone ring was damaged during installation.

Damaging the wheel speed sensor tone ring (or reluctor ring) during wheel bearing installation is a common cause of ABS light illumination. The tone ring provides the speed signal to the ABS sensor, and damage can lead to an erratic or missing signal, triggering a fault.

D. Toe misalignment

Toe misalignment causes a scrubbing action across the tire tread as the vehicle moves, leading to feathering or excessive wear on one side of the tread, depending on whether it's toe-in or toe-out.

D. The vehicle's battery voltage is too low during the relearn procedure.

Many TPMS relearn procedures require stable system voltage. Low battery voltage can disrupt the communication signals or the vehicle's ability to complete the sequence, leading to relearn failure.

B. Incorrect front toe setting.

A vehicle pulling to one side with the steering wheel offset, combined with specific tire wear patterns (outer edge wear on one side, inner edge wear on the other), is a classic indication of an incorrect front toe setting. This causes the tires to 'scrub' sideways, leading to the pull and wear.

C. Faulty TPMS sensor battery in the right rear wheel

If a TPMS sensor's battery is dead or weak, it will not be able to transmit its signal to the vehicle's receiver, preventing it from being activated or learned into the system, even if the tire pressure is correct.

A. Worn upper or lower ball joints

Excessive play when rocking the wheel at 12 and 6 o'clock is a classic indicator of worn upper or lower ball joints. This movement primarily checks vertical play in the steering knuckle, controlled by the ball joints.

A. Worn shock absorbers or struts

Cupping or scalloping wear patterns are typically caused by a tire bouncing excessively due to worn suspension components, most commonly shock absorbers or struts, leading to uneven contact with the road.

A. Stress cracks

Cracks originating from the lug nut holes are typically stress cracks, often caused by improper lug nut torque (over-tightening or uneven tightening) or repeated stress cycles, which compromise the structural integrity of the wheel.

A. Front-to-rear (front tires move straight back, rear tires move straight forward).

Directional tires are designed to rotate in only one direction for optimal performance (e.g., water dispersion). Therefore, they cannot be crossed from side to side. For AWD vehicles with directional tires, the only acceptable rotation pattern is front-to-rear, keeping them on the same side of the vehicle.

B. The vehicle requires a specific drive cycle to complete the relearn.

Many TPMS systems, even after successful sensor communication and pressure verification, require a specific drive cycle (e.g., driving above a certain speed for a period) to fully complete the relearn process and turn off the warning light.

D. To prevent the wheel from seating properly and causing runout.

Corrosion on the hub mounting surface prevents the wheel from seating flush and true against the hub. This uneven seating can cause excessive wheel runout, leading to vibrations and stress on the wheel studs, even if lug nuts are torqued correctly.

B. Perform a road force variation (RFV) measurement.

If a wheel is balanced but a vibration persists, especially at highway speeds, it often indicates a non-uniformity issue within the tire or wheel assembly itself, such as high or low spots, which is measured and corrected by a road force variation machine.

A. It indicates the lightest point of the tire, which should be aligned with the heaviest point of the wheel.

The yellow dot on a tire indicates its lightest point, while the red dot indicates the stiffest point (high point of radial force variation). Aligning the lightest point of the tire with the heaviest point of the wheel (usually where the valve stem is located) helps to minimize the amount of weight needed for balancing.

C. Rearward cross pattern (rear tires move straight forward, front tires cross to the rear).

For RWD vehicles with non-directional tires, the rearward cross pattern is recommended. This involves moving the rear tires straight to the front, and the front tires crossing to the opposite rear position. This ensures all tires spend time on the drive axle and non-drive axle positions, promoting even wear.

C. Inspect the wheel for damage and replace if runout exceeds specifications.

Excessive wheel runout will prevent proper balancing and can cause vibrations. The wheel itself must be inspected for damage and replaced if its runout is beyond manufacturer specifications, as balancing cannot correct a bent or out-of-round wheel.