ASE A4 Practice Test — Suspension & Steering

A shimmy that occurs in a specific speed window — not at low speed, not at very high speed, but in a narrow band — is a resonance vibration. Worn strut mounts allow the strut assembly to shift and wobble, and at a certain speed the natural frequency of the suspension matches the rotational speed of the wheels, creating a harmonic vibration. Above and below that speed, the frequencies do not match and the shimmy disappears. A bent rim (B) would cause a vibration that increases with speed and never goes away. Worn tie rods (C) cause wandering and poor steering response, not a speed-specific shimmy. Wheel bearing play (D) causes a humming noise and may cause a wobble that gets worse with speed, not one that appears and disappears in a specific range. The speed-window shimmy is the hallmark of a resonance issue — worn mounts, loose components, or harmonic imbalance.

When alignment is in spec and pressures are equal but the vehicle still pulls, tire conicity is the next suspect. Tire conicity is a manufacturing characteristic where the tire belt layers are slightly off-center, causing the tire to generate a lateral force — it literally steers itself to one side. Swapping the front tires side to side is the diagnostic test. If the pull switches direction (now pulls left), the tire was causing it. If the pull stays the same, the tire is not the cause and you move to other possibilities like brake drag, suspension geometry issues not captured in the alignment, or road crown sensitivity. Never replace major components (B, D) without eliminating the simplest causes first. Tire swap costs nothing and takes ten minutes. It should always be done before spending diagnostic time on more complex possibilities.

Technician A is correct. Inside edge wear is the signature of excessive negative camber — the top of the tire is tilted inward, pressing the inside edge into the pavement harder than the rest of the tread. This is true on any axle position, front or rear. Technician B is incorrect because toe misalignment causes a feathered wear pattern across the entire tread face — if you run your hand across the tread, it feels smooth one direction and rough the other, like a saw blade. Toe does not cause concentrated edge wear. Many technicians overlook rear alignment angles because they think only the front matters. On independent rear suspension vehicles, rear camber and toe are adjustable and can go out of spec from worn bushings, bent components, or impact damage. Always check all four wheels.

When a ball joint exceeds the manufacturer maximum specification for play, it must be replaced. There is no adjusting, no monitoring, no greasing it back into spec. The ball joint is a structural safety component — it connects the steering knuckle to the control arm and supports the weight of the vehicle. Excess play means the ball and socket are worn, and additional wear happens rapidly once the specification is exceeded. A ball joint failure can result in a wheel separation — the wheel literally folds under the vehicle. Do not tighten the castle nut (C) — it is not designed to take up ball joint wear. The specification exists for a reason. When the measurement exceeds the max, you replace it. This is one of the few areas in automotive repair where there is zero room for judgment calls.

Excessive positive caster actually improves straight-line stability — it increases the self-centering effect of the steering, making the vehicle feel MORE stable, not loose. Positive caster is why shopping carts track straight when pushed forward — the pivot point leads the contact point. More caster means more stability. Worn tie rod ends (A) allow slop in the steering linkage, which the driver feels as wandering. A worn center link or idler arm (C) on older parallelogram steering systems creates free play in the entire linkage, causing vague steering. Worn rack mount bushings (D) let the entire rack shift under load, creating a loose feel. When a vehicle wanders, think about what introduces free play into the steering system. Caster does the opposite — it tightens things up. EXCEPT questions test whether you understand the underlying physics, not just the symptom lists.

Both technicians are correct. Worn stabilizer bar end links (Technician A) are one of the most common causes of front-end clunks over bumps. The rubber bushings and ball sockets in the end links wear out, allowing the stabilizer bar to shift and bang against the suspension when the wheel hits a bump. Worn strut mount bearings (Technician B) sit on top of the strut tower and absorb the jolt when the strut compresses. When the bearing or the rubber isolator wears, the strut assembly clunks against the body. The way to differentiate is hand-testing. Grab the stabilizer bar near the end link and try to move it — clunk there means end links. Put your hand on the strut tower while someone bounces the corner — clunk through the body means strut mount. Both are common, both are relatively inexpensive, and both are frequently replaced together during front-end service.

Electric power steering does not use a hydraulic pump at all — it uses an electric motor attached to the steering column or rack. The EPS control module determines how much assist to provide based primarily on three inputs: vehicle speed (less assist at highway speed for better road feel, more assist at parking speed), steering wheel torque (measured by a torque sensor on the steering column — how hard you are turning), and steering angle (how far and how fast you are turning the wheel). Some systems also factor in yaw rate for stability. EPS has largely replaced hydraulic power steering because it eliminates the parasitic drag of a belt-driven pump, improves fuel economy, and allows software calibration of steering feel. Understanding EPS inputs is critical for modern vehicle diagnosis — a failed torque sensor can make the steering feel dead or erratic.

Unequal caster side to side causes the vehicle to pull toward the side with less positive caster. Positive caster creates a self-centering force in the steering — more caster means more force pulling that wheel straight ahead. When one side has more caster than the other, the side with more caster pulls harder toward center, overpowering the weaker side. The net effect is a pull toward the side with less caster. This is different from camber-related pull, which pulls toward the side with more positive camber. Unequal caster does not directly cause tire wear (A) — that is a camber or toe issue. An off-center steering wheel (C) is caused by toe misalignment, not caster. Excessive bouncing (D) is a shock or strut problem. When diagnosing a pull, always check caster side-to-side difference first — it should be within 0.5 degrees.

Both technicians are correct and both points are critical. The coil spring on a MacPherson strut is under tremendous compression — hundreds of pounds of force. If you remove the top strut nut without compressing the spring first (Technician A), the spring will launch with lethal force. Spring compressor tools are mandatory for this job. There are no shortcuts and no exceptions. After replacing the strut (Technician B), alignment must be checked because the strut is a structural part of the suspension geometry on MacPherson designs. The strut mount position directly affects camber and caster. Even a slight difference in the new strut mount position compared to the old one will change alignment angles enough to cause tire wear and handling issues. Never skip the alignment after strut replacement.

A pull during acceleration only is not a wheel bearing symptom — it is typically caused by unequal CV axle lengths (torque steer), a worn engine mount allowing the drivetrain to shift, or a brake caliper dragging. A worn wheel bearing produces a humming or growling noise (A) that changes intensity when you load or unload it by swerving — swerve right to load the left bearing, swerve left to load the right bearing. The noise gets louder on the loaded side. ABS light illumination (B) occurs because the wheel speed sensor is typically pressed into or mounted on the bearing hub — when the bearing has play, the air gap between the sensor and tone ring becomes inconsistent, causing erratic readings. Excessive play at 12 and 6 (C) indicates physical wear in the bearing races and rollers. All three are classic bearing symptoms. The acceleration-only pull is a different system.