ASE A4 Suspension and Steering flashcards

A common tire rotation strategy for front-wheel drive vehicles to promote even tire wear.

• Front tires move straight back to the rear axle.
• Rear tires move forward to the opposite side of the front axle.
• Also known as 'modified X' or 'rear cross' pattern.

Memory trick: FWD: Fronts go Back, Rears Cross to Front.

An imbalance in a front wheel assembly causes a high-frequency vibration or shimmy in the steering wheel, typically at specific speed ranges, and is corrected by dynamic wheel balancing.

• Vibration/shimmy in steering wheel
• Occurs at specific speed ranges (e.g., 40-70 mph)
• Corrected by dynamic wheel balancing

Memory trick: Wobbling wheel? Balance it, don't just align it!

A sudden alteration in a wheel's camber angle following a significant impact, often indicating bent suspension components.

• Positive camber: top of the wheel tilts outward.
• Negative camber: top of the wheel tilts inward.
• Pulls to the side with more positive camber (or less negative).

Memory trick: Pothole hit, positive camber, knuckle's bent, the car's not right!

The requirement to re-balance a tire and wheel assembly after any internal repair or dismounting.

• Ensures even weight distribution after material changes.
• Prevents vibrations and uneven tire wear.
• Crucial for maintaining ride comfort and safety.

Memory trick: After a patch, make sure the wheel is 'balanced' for a smooth ride.

Improper toe alignment causes a 'scrubbing' wear pattern across the tire tread, often resulting in feathering or accelerated wear on one side of the tire.

• Toe-in causes wear on the outer shoulder.
• Toe-out causes wear on the inner shoulder.
• Can lead to feathering (smooth on one side, sharp on the other).

Memory trick: Toe Scrapes the Tread Sideways.

Common indications of an unbalanced front wheel assembly.

• Vibration felt in the steering wheel.
• Often occurs within specific speed ranges (e.g., 40-70 mph).
• Can lead to premature steering and suspension component wear.

Memory trick: Steering wheel shakes? Front wheels are the culprits!

Identifying a faulty wheel bearing based on noise characteristics and how they change with vehicle maneuvers.

• Noise often described as grinding, roaring, or humming.
• Increases with vehicle speed.
• Changes in intensity when turning due to load shifts.

Memory trick: Turn left, load right, noise bright!

A faulty wheel bearing's noise typically gets louder when turning in the direction that loads that bearing, and quieter when turning in the opposite direction.

• Turning right loads left side bearings
• Turning left loads right side bearings
• Noise increases with load on faulty bearing

Memory trick: Turn right, load left; turn left, load right.

Warped brake rotors, which cause pulsation during braking, are often caused by improper lug nut torque, aggressive braking leading to excessive heat, or uneven cooling.

• Pulsation felt in brake pedal/steering wheel
• Commonly caused by uneven lug nut torque
• Can also be caused by overheating/uneven cooling

Memory trick: Pulsating pedal? Check the torque, not just the rotor!

Excessive negative camber causes accelerated wear on the inner edge of the tire tread due to the tire tilting inwards at the top.

• Tire top tilts inward
• Inner edge wears faster
• Can be caused by worn suspension or incorrect alignment

Memory trick: Camber's tilt tells the tale of inner or outer wear.

Reasons why a Tire Pressure Monitoring System (TPMS) might fail to successfully register new or replaced sensors.

• Low battery voltage can disrupt communication.
• Incorrect relearn procedure steps or sequence.
• Interference from other electronic devices.
• Faulty new sensor or TPMS control module.

Memory trick: Low volts make TPMS 'relearn' its lesson the hard way.

The specific central section of a tire's tread where punctures can be safely and permanently repaired according to industry guidelines.

• Excludes sidewall and shoulder areas due to high flex.
• Typically defined as the center ~2/3 to 3/4 of the tread width.
• Puncture size limits also apply (e.g., 1/4 inch diameter).

Memory trick: Sidewall leak? No fix, just replace for safety's sake!

The ABS tone ring (reluctor ring), which provides wheel speed data to the sensor, is susceptible to damage during wheel bearing or axle replacement, leading to ABS system faults and an illuminated ABS light.

• Provides wheel speed signal
• Often integrated with wheel bearing or axle
• Damage causes erratic/missing signal, triggering ABS light

Memory trick: Bearing's in, but ABS is out? Check the ring, no doubt!

Incorrect front toe causes a vehicle to pull, an offset steering wheel, and characteristic feathered or differential edge wear on the tires as they scrub against the road.

• Primary cause of vehicle pull without steering input
• Causes steering wheel offset
• Results in feathered or uneven edge tire wear

Memory trick: Pull, offset, and scrubbing wear? Toe's the true culprit there!

TPMS sensors are battery-powered, and a dead or weak battery will prevent the sensor from transmitting data, leading to relearn failures and a persistent warning light.

• Batteries are typically non-replaceable within the sensor unit.
• Expected lifespan is 5-10 years.
• Often signaled by intermittent warnings before complete failure.

Memory trick: Sensor Needs Power to Talk.

Rocking the wheel at 12 and 6 o'clock checks for vertical play, primarily indicating worn upper or lower ball joints.

• Checks vertical movement of wheel
• Primary indicator of worn ball joints
• Requires vehicle to be jacked up for accurate check

Memory trick: Twelve-six for balls, nine-three for rods.

An uneven wear pattern characterized by alternating high and low spots around the tire's circumference, resembling cups or scallops.

• Often indicative of worn suspension components.
• Commonly caused by failing shock absorbers or struts.
• Results from the tire bouncing unevenly on the road surface.

Memory trick: Bad shocks make tires 'cup' their hands for help.

Structural cracks in a wheel, often originating from high-stress points like lug nut holes, indicating compromised integrity.

• Can be caused by improper lug nut torque (over-tightening or uneven).
• Also result from impact damage or material fatigue.
• Render the wheel unsafe and require replacement.

Memory trick: Cracks at the lugs mean 'stress' and a wheel that's a bust!

Directional tires, identified by an arrow on the sidewall, must always maintain their specified rotation direction. This restricts rotation to only front-to-rear on the same side of the vehicle.

• Must maintain rotation direction
• Cannot be crossed side-to-side
• Common pattern is front-to-rear (straight rotation)

Memory trick: Arrows point forward, never across the car!

Some TPMS systems require a specific drive cycle (e.g., driving at a certain speed for a duration) to fully complete the sensor relearn process and extinguish the warning light.

• Required after sensor replacement or rotation
• Involves driving at specific speeds/durations
• Final step to clear TPMS light

Memory trick: After the scan, take a drive, then the light won't thrive!

The critical practice of ensuring the wheel hub's mating surface is free of corrosion and debris before mounting a wheel.

• Prevents improper wheel seating and runout.
• Reduces the risk of wheel vibrations.
• Ensures even distribution of clamping force from lug nuts.

Memory trick: Clean hub face, no wobble, no race!

An imbalance in a rear wheel assembly causes vibrations primarily felt in the seat, floorboard, or entire vehicle, especially at higher speeds.

• Vibration felt in seat/floorboard
• More pronounced at highway speeds
• Distinct from steering wheel vibration

Memory trick: Seat and floor = rear, Steering wheel = front.

Road Force Variation (RFV) measures the uniformity of a tire and wheel assembly under load, identifying high/low spots that cause vibrations not correctable by traditional balancing.

• Measures tire/wheel uniformity under load
• Identifies non-balance related vibrations
• Can optimize tire-to-wheel mounting position

Memory trick: Balanced but still shaking? Road force is the missing link!

Tires often have color-coded dots (yellow for lightest point, red for stiffest point/radial force variation high point) on the sidewall to assist in mounting and balancing by aligning them with corresponding points on the wheel.

• Yellow dot = lightest point of tire
• Red dot = stiffest point of tire (radial force variation high point)
• Valve stem area = usually heaviest point of wheel
• Aligning helps minimize balance weights

Memory trick: Yellow is light, red is stiff; valve stem is heavy, making a good fit!

For rear-wheel drive vehicles with non-directional tires, the rearward cross pattern is used: rear tires move straight forward, and front tires cross to the opposite rear.

• Maximizes tire life by distributing wear.
• Applies to non-directional tires only.
• Ensures all tires experience drive axle and steering axle forces.

Memory trick: RWD: Rears Go Forward, Fronts Cross Back.

The deviation of a wheel's rim from a perfectly circular shape (radial runout) or a perfectly flat plane (lateral runout).

• Measured in thousandths of an inch or millimeters.
• Excessive runout causes vibration and cannot be corrected by balancing.
• Can be caused by impacts, manufacturing defects, or corrosion.

Memory trick: Bad wheel runout? Don't balance, replace!

Identifying a loose wheel bearing by observing wheel play and its reaction to brake application.

• Excessive play at 12 and 6 o'clock often indicates a loose wheel bearing or ball joint.
• If play reduces with brake application, it confirms a loose wheel bearing.
• Brake caliper action stabilizes the rotor and hub, masking bearing play.

Memory trick: 12-6 play, brakes make it stay? Wheel bearing's gone astray!

RMA guidelines define the repairable area for punctures as the tread face, typically excluding the shoulder and sidewall areas due to high flex and stress that can compromise a plug/patch repair.

• Limited to tread area
• Excludes shoulder and sidewall
• Specific distance from sidewall/shoulder (e.g., 1 inch from sidewall for passenger tires)

Memory trick: Tread is fair game, but the shoulder and sidewall tell a different tale.

When a tire is underinflated, its shoulders (inner and outer edges) bear the majority of the load, causing accelerated wear on these areas.

• Causes wear on both inner and outer edges of the tread.
• Reduces tire's contact patch.
• Increases rolling resistance and fuel consumption.

Memory trick: Under Pressure, the Edges Crumble First.

A clean, flat, and burr-free wheel mounting surface is critical for achieving and maintaining correct lug nut torque and preventing wheel loosening.

• Ensures proper clamping force
• Prevents wheel loosening
• Corrosion or debris can compromise safety

Memory trick: Rough surface, loose nuts, bad news for the ride.

The process of re-tightening lug nuts to specification after a short period of driving following initial installation or tightening.

• Ensures proper seating of the wheel against the hub.
• Prevents loosening due to settling or vibration.
• Typically recommended after 50-100 miles of driving.

Memory trick: After tightening, always 're-check' the nuts to keep wheels on track.

Road Force Variation (RFV) measures the change in force exerted by a tire as it rolls under load. High RFV is corrected by match-mounting the tire to the wheel to offset the tire's stiff spot with the wheel's low spot.

• Caused by tire uniformity issues or excessive wheel runout.
• Causes vibrations, especially at highway speeds.
• Match-mounting is the primary correction method.

Memory trick: High Force, Match-Mount to Smooth Course.

Diagnosing steering wheel vibrations involves systematically eliminating common causes, especially those related to rotating components.

• Speed-sensitive vibrations often relate to tires, wheels, or driveline.
• Steering wheel vibration points to front-end issues.
• Bent rims can cause vibration even if balanced.
• Eliminate tire balance, wheel bearings, and suspension issues first.

Memory trick: Wheels Wobble When Worn.

Binding in the steering column, often due to a corroded or worn U-joint, creates mechanical resistance that increases steering effort.

• Causes 'heavy' steering, especially at low speeds.
• May not produce noise or DTCs related to power assist.
• U-joints are common culprits due to corrosion or lack of lubrication.
• Requires physical inspection and manipulation of the steering column.

Memory trick: Binding Blocks Basic Burdens.

Air entering the hydraulic power steering system leads to cavitation, resulting in noise, reduced assist, and foamy fluid.

• Commonly caused by loose low-pressure hose connections or faulty pump seals.
• Produces a whining or groaning noise.
• Visible as air bubbles or foam in the fluid reservoir.
• Can damage pump and other components over time.

Memory trick: Air Ingress Agitates Assist.

A worn or loose universal joint (U-joint) in the steering column can cause distinct clunking or popping noises, particularly during steering input or when suspension components move.

• Connects steering column to steering gear.
• Allows for angle changes between components.
• Failure manifests as clunking or popping noises.
• Can also lead to excessive steering play or binding.

Memory trick: Joint Jiggles Generate Jumps.

A malfunctioning power steering pump often presents with distinct symptoms related to its inability to maintain proper hydraulic pressure.

• Groaning or whining noise, especially when turning.
• Increased steering effort, particularly at low speeds or full lock.
• Foamy or dark power steering fluid.
• Fluid leaks around the pump or reservoir.

Memory trick: Pump Problems Produce Pressure Pains.

Excessive free play in a steering gearbox refers to unwanted movement between the input (steering shaft) and output (pitman arm/rack) components, leading to loose steering.

• Manifests as excessive steering wheel free play.
• Can be caused by internal wear of gears or bearings.
• May also be due to improper adjustment of the gear.
• Reduces steering precision and vehicle control.

Memory trick: Loose Gear Gives Great Grievances.

Diagnosing EPS systems involves interpreting DTCs, understanding system components, and recognizing the absence of hydraulic fluid.

• EPS systems use electric motors for assist, not hydraulic pumps.
• DTCs are crucial for pinpointing electronic faults.
• C0550 often indicates internal module or motor circuit issues.
• Loss of assist and warning lights are common failure symptoms.

Memory trick: Electric Problems Elicit Error Codes.

An off-center steering wheel, despite correct alignment specifications and no vehicle pull, typically results from improper tie rod adjustment during the alignment procedure.

• Occurs when total toe is correct but the steering wheel is not centered.
• One tie rod is too long, the other too short.
• Vehicle drives straight, but wheel is crooked.
• Requires re-centering the steering wheel and adjusting tie rods equally.

Memory trick: Tie Rod Tweak Twists The Wheel.

A pressure test evaluates the power steering pump's ability to generate and maintain specified hydraulic pressure, particularly at full steering lock.

• Connects a gauge to the high-pressure line.
• Tests maximum pressure at full lock (briefly).
• Low pressure indicates a weak or faulty pump.
• Excessive noise during test can also point to pump issues.

Memory trick: Pump Pressure Problems Produce Poor Performance.

Identifying the source of a power steering fluid leak requires careful inspection, often focusing on connection points and hose integrity.

• Leaks at fittings often indicate seal (O-ring/washer) failure.
• Leaks along the hose body suggest hose degradation or damage.
• Pump leaks occur at shaft seals or housing gaskets.
• Fluid type and color can sometimes indicate the component type or age.

Memory trick: Seals Stop Seepage Seriously.

Tie rod boots protect the inner and outer tie rod joints from contamination and retain lubricating grease, ensuring their longevity and proper function.

• Prevents dirt, water, and debris from entering the joint.
• Keeps lubricating grease inside the joint.
• A torn boot leads to premature joint wear.
• Inspection of boots is crucial during routine maintenance.

Memory trick: Boot Breakage Brings Bad Bearings.

Internal play within a steering gear (rack and pinion or recirculating ball) refers to excessive clearance between its internal components, leading to a 'dead spot' in steering response.

• Manifests as a 'dead spot' or looseness in the steering wheel.
• Occurs before road wheels respond to steering input.
• Caused by wear in gears, bearings, or rack bushings.
• Reduces steering precision and control.

Memory trick: Internal Gear Gaps Generate Grievances.

Intermittent electrical problems in electronically controlled power steering systems often manifest as inconsistent assist and communication errors.

• Commonly due to loose, corroded, or damaged wiring/connectors.
• Affects power supply, ground, or data communication.
• Leads to unpredictable system behavior.
• Often indicated by intermittent DTCs or communication errors.

Memory trick: Corroded Contacts Cause Chaotic Control.

Gradual wear of internal components (e.g., vanes, rotor, cam ring) within a hydraulic power steering pump, leading to reduced efficiency and lower pressure output, especially at low engine RPMs.

• Symptoms include heavy steering at idle, improving with RPM.
• Pressure tests show low pressure at idle, normal at higher RPMs.
• Requires pump replacement.

Memory trick: Low RPM struggle means pump is tired.

Runout compensation calibrates the alignment sensors to account for wheel and adapter imperfections. Failures often stem from unstable sensor mounting or issues during wheel rotation.

• Compensates for wheel/adapter runout.
• Requires stable sensors and smooth wheel rotation.
• Loose sensors are a primary cause of failure.

Memory trick: Runout's turn, if sensors shake, faulty readings it will make.

Thrust angle is the angle of the rear axle relative to the vehicle's centerline. A non-zero thrust angle causes the vehicle to 'dog-track' – travel with the rear of the vehicle offset to one side.

• Positive thrust angle: rear axle points right, rear shifts right.
• Negative thrust angle: rear axle points left, rear shifts left.
• Always results in an off-center steering wheel when driving straight.

Memory trick: Thrust negative, rear goes left; like a crab, it's put to the test!

A significant difference or out-of-spec reading for SAI between the left and right sides typically indicates bent or damaged suspension components.

• SAI is non-adjustable.
• Set by suspension design.
• Discrepancies point to component damage.

Memory trick: SAI is fixed; if it's broken, something is bent.

Total toe refers to the combined toe angle of both wheels on an axle. Negative total toe indicates toe-out, and positive total toe indicates toe-in. Tie rod adjustments change toe.

• Negative total toe = toe-out (front of wheels apart).
• Positive total toe = toe-in (front of wheels closer).
• Shortening tie rods reduces toe-out or increases toe-in.
• Lengthening tie rods increases toe-out or reduces toe-in.

Memory trick: Toe's sign tells its tale, short's for out, long's for in, never fail.

Thrust angle is the direction the rear wheels are pointing relative to the vehicle's centerline. A non-zero thrust angle causes the vehicle to 'dog-track' and often leads to an off-center steering wheel and vehicle pull.

• Positive thrust angle: rear axle points right.
• Negative thrust angle: rear axle points left.
• Causes dog-tracking and a steering wheel offset.

Memory trick: Thrust to the right, pull to the right; thrust to the left, pull with all your might!

Excessive play in a steering column universal joint (U-joint) causes a 'loose' steering feel, slack, and a noticeable delay between steering wheel rotation and the movement of the steering rack's input pinion.

• Connects sections of steering shaft.
• Allows for angular movement.
• Wear causes lost motion and delay in steering.

Memory trick: Shaft moves, pinion waits? U-joint's loose, mate!

Intermittent communication errors between an EPS control module and other vehicle modules (e.g., BCM) typically indicate a fault in the CAN bus wiring, connectors, or network integrity, requiring inspection of these components.

• DTCs point to network issue.
• Look for wiring damage, corrosion, loose pins.
• CAN bus is critical for module communication.

Memory trick: Communication broken? Check the wires and connectors.

A 'popping' or 'clicking' noise from the front suspension, especially when turning the steering wheel at low speeds or articulating the suspension, is often caused by a worn or damaged strut bearing (mount) that prevents smooth rotation of the strut.

• Allows strut/spring to rotate with steering.
• Wear causes binding and noise.
• Noise is typically heard from top of strut tower.

Memory trick: Clicking when turning? Check the strut bearing's spin.

When a diagnostic trouble code indicates a 'circuit malfunction' for a sensor, the initial diagnostic step involves inspecting the electrical connections and wiring related to that sensor.

• DTCs often point to specific circuits.
• Check physical connections first.
• Wiring integrity is crucial for sensor operation.

Memory trick: Circuit fault? Check the wires, and the connections are tight!

Caster is a primary contributor to steering stability and returnability. Insufficient positive caster leads to light, wandering steering, poor return-to-center, and sometimes heavy steering effort, while excessive positive caster can make steering heavy.

• Positive caster provides self-aligning torque.
• Insufficient positive caster: poor returnability, light steering.
• Excessive positive caster: heavy steering, good returnability.
• Zero or negative caster: unstable, poor returnability.

Memory trick: Caster is like a shopping cart wheel: too little, it wobbles; too much, it's hard to turn.

Significant deviations in Included Angle, especially when accompanied by out-of-spec camber, often point to a bent spindle or steering knuckle, as SAI (part of IA) is non-adjustable.

• IA = SAI + Camber.
• SAI is fixed by design.
• IA issues imply damage if camber cannot explain it.

Memory trick: IA + Camber = SAI, if IA is off, check for bent metal.

The difference between the left and right caster angles. A small split is acceptable, but excessive split can cause a vehicle pull.

• Influences steering stability and returnability.
• Affects steering effort.
• Should be within manufacturer's specified tolerance (typically 0.5 - 1.0 degree).

Memory trick: Both the individual and the difference must be in the green.

Caster split (difference between left and right caster) can cause vehicle pull and affect steering returnability. To correct, adjust the lower caster to match the higher, or bring both within spec, prioritizing the side that is furthest from spec.

• Less positive caster causes pull towards that side (or more positive caster causes pull away).
• Equalizing caster improves straight-line stability and returnability.
• Adjust the wheel with the most significant deviation from spec.

Memory trick: Pull to the left, caster's too low; raise the left, make the steering flow.

Steering Axis Inclination (SAI) is a non-adjustable angle. A significant difference in SAI between the left and right sides typically indicates a bent or damaged component in the steering or suspension system.

• SAI is a fixed, non-adjustable angle.
• Determined by the vehicle's design (knuckle, strut).
• Split SAI often points to structural damage from impact.

Memory trick: SAI's fixed, a split's a clue, component damage, often new.