- ASE A4
- The ASE Suspension & Steering certification test in the Automobile (A-series) program; covers steering, suspension, wheel alignment, and tire service.
- Rack and pinion
- A steering gear where a pinion on the steering shaft moves a toothed rack side to side; the rack ends connect through tie rods to the knuckles. Standard on most cars.
- Recirculating ball
- A steering gearbox where a worm gear turns a sector shaft through ball bearings, moving a pitman arm and linkage. Common on trucks and older rear-drive cars.
- Pinion gear
- The small gear on the steering shaft that meshes with the rack to convert the steering wheel's rotation into side-to-side rack motion.
- Steering rack
- The toothed bar in a rack-and-pinion gear that moves left and right; its ends connect to the inner tie rods.
- Pitman arm
- An arm splined to a recirculating-ball gearbox's sector shaft that turns the gear's motion into side-to-side movement of the steering linkage.
- Idler arm
- A pivoting support opposite the pitman arm in a parallelogram linkage; keeps the center link level. When worn, it causes steering play and wander.
- Center link (drag link)
- The bar in a parallelogram linkage connecting the pitman arm and idler arm, to which the inner tie rods attach.
- Tie rod
- A link connecting the steering gear or center link to the steering knuckle; transmits steering motion to the wheel.
- Outer tie-rod end
- The ball-and-socket joint that connects the tie rod to the steering knuckle; wear causes play and erratic toe.
- Inner tie-rod end
- The joint connecting the tie rod to the steering rack or center link; on a rack it is protected by the bellows boot.
- Tie-rod sleeve (adjusting sleeve)
- The threaded sleeve between the inner and outer tie-rod ends that is turned to set front toe.
- Steering knuckle
- The part that holds the wheel hub/bearing and pivots on the ball joints (or strut) so the wheel can steer.
- Power steering pump
- A belt-driven pump that supplies pressurized fluid to a hydraulic steering gear to reduce steering effort. A failing pump causes hard steering or a whine.
- Power steering fluid
- Hydraulic fluid that transmits pressure and lubricates the steering gear. Low fluid or air causes hard steering, whining, or groaning.
- Electric power steering (EPS)
- Power assist from an electric motor instead of a hydraulic pump; more efficient and enables features like lane keeping.
- Hydraulic power steering
- Power assist using a belt-driven pump, pressurized fluid, and a control valve in the steering gear.
- Steering gear (gearbox)
- The assembly that multiplies the driver's effort and converts steering-wheel rotation into the motion that steers the wheels.
- Steering damper (stabilizer)
- A shock absorber mounted in the steering linkage (common on trucks/4x4s) that dampens road shock and reduces steering shimmy.
- Steering column
- The shaft assembly connecting the steering wheel to the steering gear, usually with a collapsible feature for crash safety.
- Universal joint (steering)
- A flexible coupling in the steering shaft that lets the column change angle while still transmitting rotation.
- Hard steering
- Increased steering effort in both directions; causes include low power-steering fluid, a worn pump, a loose belt, or low tire pressure.
- Steering wander
- The vehicle drifting and needing constant correction; causes include worn linkage, low caster, or unequal tire pressure.
- Excessive steering play
- Free play in the steering wheel before the wheels move; usually worn tie-rod ends, idler/pitman arm, or gearbox wear.
- Memory steer
- The vehicle holding a steered direction after a turn instead of returning; often a binding strut mount or upper bearing.
- Power-steering whine
- A whine that rises and falls with steering effort; classically a low fluid level, air in the system, or a failing pump.
- Steering wheel free play
- The amount the steering wheel turns before the road wheels move; excessive play means wear in the gear or linkage.
- Clock spring (SRS coil)
- A coiled ribbon connector in the steering column that keeps the airbag and steering-wheel controls connected as the wheel turns.
- Variable-assist steering
- Power steering that provides more assist at low speed (parking) and less at high speed for road feel.
- Steering gear adjustment
- Setting the sector-shaft (over-center) preload in a recirculating-ball gearbox to remove excess play without binding.
- Bellows boot (rack)
- A flexible rubber boot that protects the inner tie-rod end and rack from dirt and moisture; a torn boot leads to wear.
- Steering effort test
- Measuring the force needed to turn the wheel (often with a spring scale) to confirm proper power-assist operation.
- Drive belt (power steering)
- The belt that drives the power-steering pump; a loose or glazed belt causes hard steering and a squeal.
- Control valve (steering)
- The valve in a hydraulic gear that directs pressurized fluid to assist in the direction the driver is turning.
- Rack-and-pinion mounting bushings
- Bushings that secure the steering rack to the body/subframe; worn bushings cause a clunk and vague steering.
- Toe set at tie rods
- On both rack-and-pinion and recirculating-ball systems, front toe is adjusted at the tie-rod sleeves.
- Sector shaft
- The output shaft of a recirculating-ball gearbox that the pitman arm is splined to.
- Worm gear
- The input gear in a recirculating-ball box that the steering shaft turns; ball bearings recirculate along its threads.
- Steering shimmy
- A side-to-side oscillation felt in the steering wheel, usually from tire imbalance, a bent wheel, or worn linkage.
- Tilt/telescoping column
- An adjustable steering column that changes wheel angle and reach for driver fit.
- Power-steering pressure test
- Using a gauge to verify the pump produces specified pressure and the system holds it, diagnosing a weak pump or restriction.
- Steering pull vs. wander
- A pull constantly tugs one direction (alignment/tire); wander drifts both ways and needs constant correction (worn linkage/low caster).
- Cardan/intermediate shaft
- The lower steering shaft linking the column to the gear; worn U-joints in it cause a clunk or notchy steering feel.
- Lubricating steering linkage
- Greasing serviceable tie-rod ends, ball joints, and idler arms (where fittings exist) to extend joint life.
- Steering binding
- Resistance or catching in the steering travel; can come from a tight gear adjustment, a seized joint, or a damaged column.
- MacPherson strut
- A suspension unit combining the shock absorber and a structural member, with the coil spring around it; the upper mount often carries the steering pivot bearing.
- Shock absorber
- A hydraulic damper that controls spring oscillation so the tire stays on the road. Worn shocks cause float, nose dive, and cupped tire wear.
- Coil spring
- A spring that supports vehicle weight and absorbs bumps. A sagging or broken coil lowers ride height and changes alignment angles.
- Leaf spring
- A stack of curved steel plates, mainly on truck rear axles, that supports load and locates the axle.
- Torsion bar
- A spring that resists twisting; used on some front suspensions, with ride height adjusted by an anchor bolt.
- Control arm
- A suspension arm (upper and/or lower) that locates the wheel and connects it to the frame through bushings and a ball joint.
- Ball joint
- A pivoting connection between the control arm and steering knuckle that lets the wheel move up/down and steer. A worn one clunks, wanders, and wears tires.
- Loaded ball joint
- A ball joint that carries vehicle weight; checked with a dial indicator against the wear spec, with the load supported correctly.
- Unloaded (follower) ball joint
- A ball joint that does not carry weight; checked for any play by feeling for movement.
- Ball-joint wear indicator
- A built-in feature (such as a grease-fitting boss that recedes) showing when a ball joint is worn beyond spec.
- Control-arm bushing
- A rubber or polyurethane bushing cushioning the control-arm pivot; worn bushings cause clunks, alignment drift, and wander.
- Sway bar (stabilizer bar)
- A bar connecting left and right suspension that twists in turns to resist body roll. Worn links or bushings cause a clunk over bumps.
- Sway-bar end link
- The link connecting the sway bar to the suspension; a worn or broken link causes a rattle/clunk and more body roll.
- Strut mount
- The upper mounting that secures the strut to the body and often houses the bearing the strut pivots on for steering.
- Strut bearing
- The bearing in the upper strut mount that lets the strut rotate as the wheel steers; binding causes memory steer or a creak.
- Spring seat / isolator
- The seat and rubber isolator that locate the coil spring and quiet it; a damaged isolator causes a creak or clunk.
- Jounce bumper (bump stop)
- A rubber/foam stop that limits suspension travel and prevents metal-to-metal bottoming during a hard compression.
- Strut rod (radius rod)
- A rod that locates the lower control arm fore-and-aft; a worn strut-rod bushing causes a clunk under braking and caster change.
- Bounce test
- Pushing down hard on a corner and releasing; a good shock stops the body after about one rebound, a worn one bounces two or more times.
- Nose dive
- Excessive front-end dip during braking, a classic sign of worn front shocks or struts.
- Body float
- A continuing up-and-down motion after a bump, indicating worn dampers that no longer control the spring.
- Ride height
- The designed distance between the body/frame and the ground; incorrect ride height (sagged springs) throws off camber and caster.
- Curb riding height
- The vehicle's measured height at normal load; measured before alignment because it affects the angles.
- Air suspension
- A suspension using air springs (bags) and a compressor to support load and, on some systems, adjust ride height automatically.
- Electronic/adaptive shocks
- Dampers whose firmness the vehicle adjusts electronically for ride and handling, often with a selectable mode.
- Strut cartridge
- A replaceable damping unit inside a serviceable strut housing, replacing the worn internals without the whole strut.
- Spring compressor
- A tool that safely compresses a coil spring to remove or install it on a strut; required because the spring stores dangerous energy.
- Wheel bearing
- The bearing that lets the wheel hub spin freely; a worn bearing causes a growling noise that changes with speed and play at the wheel.
- Hub assembly (bearing)
- A sealed, pre-set hub-and-bearing unit replaced as a whole; common on modern vehicles in place of serviceable bearings.
- Wheel-bearing play check
- Rocking the tire top-to-bottom (12 and 6 o'clock) to feel for looseness that points to a worn bearing.
- Coil-over suspension
- A shock or strut with the coil spring mounted over it as one assembly, allowing ride-height/preload adjustment on some designs.
- Upper control arm
- The upper locating arm in a short-long arm (SLA) suspension; works with the lower arm to control camber through travel.
- Lower control arm
- The main lower locating arm that carries much of the suspension load and the lower ball joint.
- Short-long arm (SLA) suspension
- An independent design with unequal-length upper and lower control arms, giving good camber control in travel.
- Spring sag
- A spring that has weakened and lost height, lowering ride height and altering camber/caster; replace as a pair.
- Knuckle / spindle
- The component holding the wheel bearing/hub that pivots to steer; a bent spindle shows as unequal included angle.
- Suspension clunk diagnosis
- A clunk over bumps usually traces to a worn ball joint, control-arm bushing, sway-bar link, or strut mount.
- Creak in turns
- Often a dry or worn bushing, strut bearing, or ball joint; lubrication or replacement is the fix.
- Cradle/subframe
- The structure that mounts the engine, lower control arms, and steering rack; a shifted cradle changes alignment.
- Track bar (panhard rod)
- A lateral link that locates a solid axle side-to-side; a worn track-bar bushing lets the axle shift and causes wander.
- Stabilizer bushing
- The rubber bushing that mounts the sway bar to the frame; when worn it rattles and lets the bar move.
- Shock fluid leak
- Oil running down the shock/strut body condemns the unit; the seals have failed and damping is lost.
- Independent suspension
- A design where each wheel moves independently, improving ride and tire contact compared with a solid axle.
- Solid (live) axle
- A single beam connecting both wheels; simple and strong, common on truck rear axles, but one wheel's motion affects the other.
- Bump steer
- Unwanted toe change as the suspension moves up and down, from worn parts or improper geometry, causing darting over bumps.
- Camber
- The inward or outward tilt of the wheel viewed from the front. Excess positive wears the outer tire edge; excess negative wears the inner edge.
- Positive camber
- The top of the wheel tilts outward. Too much positive camber wears the outer edge of the tire.
- Negative camber
- The top of the wheel tilts inward. Too much negative camber wears the inner edge of the tire.
- Caster
- The forward or rearward tilt of the steering axis viewed from the side. Positive caster aids straight-line stability and steering return; no direct tire wear.
- Positive caster
- The steering axis tilts rearward at the top. Improves high-speed stability and self-centering, at the cost of slightly heavier steering.
- Negative caster
- The steering axis tilts forward at the top. Lightens steering but reduces stability and return, allowing wander.
- Toe
- Whether the front edges of the wheels point inward (toe-in) or outward (toe-out) viewed from above. The most wear-sensitive angle; set last.
- Toe-in
- The front edges of the wheels point toward each other. A small amount compensates for forces that try to spread the wheels while driving.
- Toe-out
- The front edges of the wheels point away from each other; used as toe-out-on-turns for cornering geometry, but static toe-out causes instability.
- Feathered tire wear
- A saw-tooth wear pattern across the tread caused by incorrect toe dragging the tire sideways as it rolls.
- Thrust angle
- The direction the rear axle actually points relative to the vehicle centerline. A non-zero angle makes the steering wheel off-center and the vehicle dog-track.
- Thrust line
- The line bisecting the rear toe; a four-wheel alignment sets front toe to this line to keep the steering wheel centered.
- Dog-tracking
- When the rear wheels don't follow the fronts because of a thrust-angle error, so the vehicle moves slightly sideways.
- Steering axis inclination (SAI)
- The inward tilt of the steering axis viewed from the front; a built-in, non-adjustable angle used with the included angle to find bent parts.
- Included angle
- The sum of SAI and camber. If camber differs side-to-side but the included angle is equal, a part is bent (spindle or strut).
- Scrub radius
- The distance between where the steering axis and the tire centerline meet the road; affects steering feel and the pull from a low tire.
- Setback
- A condition where one front wheel sits farther back than the other, usually from collision damage or worn parts.
- Toe-out on turns (TOOT)
- The geometry (Ackermann) that makes the inside wheel turn sharper than the outside in a corner; a wrong reading suggests a bent steering arm.
- Pull diagnosis
- A steady pull goes toward the side with more positive camber or less positive caster; a tire can also cause a pull.
- Tire pull vs. alignment pull
- Swap the front tires side-to-side; if the pull moves with the tire, it's a tire (radial) pull, not the alignment.
- Four-wheel alignment
- An alignment that measures all four wheels and sets front toe to the rear thrust line; needed when the rear toe is off.
- Two-wheel (front) alignment
- Adjusting only the front wheels; acceptable when the rear is non-adjustable and the thrust angle is within spec.
- Order of alignment adjustment
- Caster first, then camber, then toe last — because changing caster or camber changes toe.
- Centering the steering wheel
- Setting front toe with the steering wheel held straight so the wheel is centered when the vehicle tracks straight.
- Pre-alignment inspection
- Checking tire condition/pressure, ride height, and all steering/suspension joints before measuring — a worn part fails an alignment.
- Alignment specifications
- The manufacturer's target angles (and tolerances) for camber, caster, and toe that the technician aligns to.
- Camber adjustment methods
- Eccentric cams, shims, slotted mounts, or moving the strut/control arm — depends on the suspension design.
- Caster adjustment methods
- Shims, eccentric cams, or moving the strut rod/control arm fore-and-aft, depending on the suspension.
- Toe adjustment
- Turning the tie-rod sleeves to bring toe to spec; equal length on each side keeps the steering wheel centered.
- Camber/caster gauge
- The alignment-machine sensor head mounted to the wheel that reads camber and caster against the targets.
- Turning radius (steering angle)
- The maximum the wheels can turn; turntables (turn plates) measure it during the alignment.
- Cross camber / cross caster
- The side-to-side difference in camber or caster; too much cross value causes a pull.
- Alignment rack & turn plates
- The lift and rotating plates that let the wheels move freely while the heads measure the angles.
- Road-test after alignment
- Driving the vehicle to confirm it tracks straight, returns to center, and the steering wheel is level.
- Bent strut/spindle check
- Using SAI and included angle: equal SAI but unequal camber/included angle means a bent strut or spindle, not an adjustment.
- Why caster has no tire wear
- Caster is a directional-stability angle, so it affects pull and return but not tread wear directly the way camber and toe do.
- Effect of low caster
- Wandering, light steering, and poor return to center; the vehicle feels darty and unstable at speed.
- Effect of ride height on alignment
- Sagged springs change camber and caster, so ride height must be correct before aligning.
- Toe and tire wear link
- Even a small toe error drags the tire sideways every mile, making toe the biggest single cause of fast tire wear.
- Memory steer vs. torque steer
- Memory steer = vehicle holds a turned direction (binding part); torque steer = pull under acceleration on FWD from unequal driveshaft forces.
- Tire
- The flexible rubber component that grips the road, supports load, and cushions bumps; the only contact between vehicle and road.
- Both-shoulder tire wear
- Wear on both outer edges with a good center indicates under-inflation — low pressure lets the shoulders carry the load.
- Center tire wear
- Wear in the center with good shoulders indicates over-inflation — high pressure bulges the center to carry the load.
- Cupping (scalloping)
- Scalloped dips around the tread from the tire bouncing — a sign of worn shocks/struts, a bent wheel, or severe imbalance.
- Tire balancing
- Adding weights so the assembly spins without vibration. An out-of-balance front tire causes a steering-wheel shimmy at highway speed.
- Static imbalance
- A heavy spot causing an up-and-down (tramp) vibration; corrected by balancing in a single plane.
- Dynamic imbalance
- A heavy spot off the centerline causing a side-to-side shimmy; corrected by balancing in two planes.
- Tire rotation
- Moving tires to different positions in a recommended pattern to even out wear and extend tire life.
- Run-flat tire
- A tire with reinforced sidewalls that lets the vehicle be driven a limited distance and speed after losing air pressure.
- TPMS
- Tire Pressure Monitoring System — sensors that warn the driver when a tire's pressure drops significantly below the recommended value.
- Direct vs. indirect TPMS
- Direct uses a pressure sensor in each wheel; indirect infers low pressure from wheel-speed (ABS) data differences.
- Tire sidewall markings
- The molded info giving size, load index, speed rating, and construction (such as P215/65R15) used to select the correct tire.
- Load index
- A number on the sidewall indicating the maximum weight a tire can safely carry at its rated pressure.
- Speed rating
- A letter on the sidewall indicating the maximum sustained speed a tire is designed to handle.
- Radial tire
- A tire whose body plies run radially (across the tread) with stabilizing belts; the standard modern construction for ride and tread life.
- Tread wear indicator (wear bar)
- Raised bars in the tread grooves; when the tread is worn level with them (about 2/32 inch), the tire is legally worn out.
- Tire mounting
- Installing a tire on a wheel with a tire machine, lubricating the bead and seating it without exceeding the bead-seat pressure limit.
- Bead seating
- Inflating a mounted tire so its beads snap onto the rim's bead seats; never exceed the recommended seating pressure.
- Lug-nut torque
- Tightening wheel lug nuts to the specified value in a star (crisscross) pattern to seat the wheel evenly and avoid warped rotors.
- Star (crisscross) tightening pattern
- The pattern for tightening lug nuts so clamping force is even across the wheel and the wheel/rotor doesn't distort.
- Tire pressure (cold)
- Pressure is set when the tires are cold; driving heats the air and raises pressure, so check before driving.
- Placard pressure
- The vehicle's recommended tire pressure on the door-jamb sticker — use this, not the max pressure on the tire sidewall.
- Tire truing
- Shaving a small amount of rubber to make a tire perfectly round, correcting a vibration from an out-of-round tire (rarely done today).
- Tire/wheel runout
- How much a tire or wheel wobbles (radial = up/down, lateral = side-to-side); excess runout causes a vibration balancing can't fix.
- Road-force balancing
- Balancing that also presses a roller on the tire to find stiffness variation, curing vibrations simple balancing misses.
- Bent wheel
- A wheel with excess runout (often from a pothole) that causes a vibration or wobble; it cannot be balanced out and must be repaired or replaced.
- Tire rotation patterns
- Recommended schemes (such as forward-cross or rearward-cross) that move tires to equalize wear based on drive type and tire directionality.
- Directional tire
- A tire designed to roll one way (arrow on the sidewall); it can only be rotated front-to-back on the same side, not crossed.
- Spare tire pressure
- The spare's inflation should be checked regularly (when checking the other tires) so it is usable in an emergency.
- Tire wear summary
- Both shoulders = under-inflation; center = over-inflation; one edge = camber; feathered = toe; cupping = worn shocks/bent wheel.
- Power-steering reservoir
- The tank that holds power-steering fluid and lets the system draw and return fluid; a low level causes a whine and hard steering.
- Bleeding power steering
- Removing trapped air after service by cycling the steering lock-to-lock so the pump stops whining and assist is consistent.
- Steering linkage inspection
- Shaking each joint with the wheels supported to feel for play in tie-rod ends, idler arm, and pitman arm.
- Parallelogram steering linkage
- A recirculating-ball layout with a pitman arm, idler arm, center link, and two adjustable tie rods forming a parallelogram.
- Steering gear mounting
- Bolts and bushings securing the gear to the frame/subframe; loose mounts cause clunks and vague steering.
- Steering return (self-centering)
- The tendency of the steering to return to center after a turn, provided largely by positive caster.
- Tie-rod end inspection
- Checking for play and a torn boot; a loose outer end causes toe change, wander, and uneven tire wear.
- Steering noise (clunk)
- A clunk when turning or over bumps can be a worn U-joint, loose rack mount, or worn linkage joint.
- Strut replacement note
- Replacing a strut changes camber/caster on many designs, so a wheel alignment is required afterward.
- Shock vs. strut
- A shock only damps motion; a strut also structurally locates the wheel and carries the spring and steering pivot.
- Wheel-bearing noise
- A growl or hum that changes with speed and may change when turning; worn bearings also create play at the wheel.
- Sealed hub unit replacement
- Replacing the whole pre-set hub-bearing assembly rather than repacking; common on modern vehicles.
- Worn bushing symptoms
- Clunks, alignment drift, wander, and uneven tire wear; cracked or collapsed rubber confirms it.
- Ackermann steering geometry
- The geometry that makes the inside wheel turn more sharply than the outside in a turn so both track without scrubbing.
- Suspension travel (jounce/rebound)
- Jounce is upward compression, rebound is downward extension; bump stops and dampers control the limits.
- Anti-dive / anti-squat geometry
- Suspension geometry that resists nose-dive under braking and rear squat under acceleration for a more level ride.
- Camber and tire contact
- Camber affects how the tread contacts the road; large camber tilts the contact patch and wears one edge.
- Caster sweep (measuring caster)
- Caster is not direct-read; the alignment machine calculates it by turning the wheels a set amount and reading camber change.
- Rear toe
- Toe at the rear axle; unequal rear toe creates a thrust-angle error, an off-center steering wheel, and rear tire wear.
- Rear camber
- Camber at the rear wheels; excess wears the rear tire edges and, if adjustable, is corrected with shims or cams.
- Alignment angle that is set last
- Toe — because adjusting caster or camber changes toe, so toe is always set after them.
- Symptom of excess toe-in
- Feathered tire wear with the sharp edges pointing outward, plus a slight loss of cornering bite.
- Symptom of excess toe-out
- Feathered wear pointing inward and a darty, unstable straight-line feel.
- Pulling toward more positive camber
- With a side-to-side camber difference, the vehicle pulls toward the wheel with the more positive (outward-leaning) camber.
- Pulling toward less positive caster
- With a caster difference, the vehicle pulls toward the side with the less positive (lower) caster.
- Brake pull vs. alignment pull
- Brake pull appears only while braking (a brake fault); alignment/tire pull is constant.
- Tire conicity pull
- A built-in radial-tire defect that makes the tire pull like a cone; swapping the tire side-to-side moves the pull.
- Specs: preferred vs. tolerance
- Alignment specs give a preferred target and an acceptable range; aim for preferred and keep side-to-side differences small.
- Wheel-speed vibration vs. balance
- A vibration that rises smoothly with speed and smooths out is usually tire balance or runout, not the engine.
- Patch/plug tire repair limits
- Repairs are allowed only in the tread area within size limits; sidewall and shoulder punctures are not repairable.
- Tire age (date code)
- The DOT date code gives the week/year of manufacture; tires age and should be inspected/replaced regardless of tread after several years.
- Penny / tread-depth test
- Measuring tread depth (or using a tread-depth gauge); about 2/32 inch remaining means the tire is worn out.
- Wheel weights placement
- Clip-on weights go on the rim flange and adhesive weights inside the barrel; placement comes from the balancer.
- Match-mounting
- Aligning the tire's high spot to the wheel's low spot (often paint dots) to minimize runout and vibration.
- Lug-nut over-torque damage
- Over-tightening lug nuts can warp brake rotors and stretch studs; always torque to spec.
- Re-torque after wheel service
- Checking lug-nut torque again after a short drive, because seating can let them relax, especially on alloy wheels.
- Spare types
- A full-size spare matches the road tires; a compact (temporary) spare is for limited distance and reduced speed.
- Snow/winter tire
- A tire with a softer compound and aggressive sipes for grip in cold and snow; identified by a mountain-snowflake symbol.
- Tire inflation and load
- Pressure must match the load; under-inflation overheats and wears the shoulders, raising the risk of a blowout.
- Technician A / Technician B
- The signature ASE format: judge each technician's statement separately as true or false, then choose A only, B only, both, or neither.
