ASE A4 cheat sheet

Steering gear ratio = steering wheel degrees divided by road wheel degrees; a numerically higher ratio means lower steering effort and slower response.

Rack-and-pinion: pinion rotation moves the rack laterally; inner tie rod sockets thread into the rack ends, and play is checked by rocking the tire at the 3 and 9 o'clock positions.

Recirculating-ball gear uses a worm shaft, recirculating ball nut, sector shaft, and pitman arm; both worm bearing preload and sector shaft mesh preload are adjustable.

Hydraulic power steering pump relief pressure is typically about 1,000-1,500 psi; a flow control valve limits flow at high engine speed to preserve road feel.

Electric power steering relies on a torque sensor plus steering angle sensor plus assist motor; a detected fault normally defaults the system to manual steering and sets a DTC.

Included angle = SAI + camber; it is not adjustable, so a value outside spec indicates a bent knuckle, spindle, or strut.

Parallelogram linkage consists of pitman arm, idler arm, center link, and tie rod assemblies; a worn idler arm bushing changes toe dynamically as the linkage loads and unloads.

Free play is measured at the steering wheel rim with the wheels straight ahead; excess play is traced in order from the wheel through the column joints, gear, and tie rods.

Bleed a hydraulic system lock-to-lock with the front wheels off the ground; whine or growl after bleeding usually indicates aeration or a restricted return line.

A MacPherson strut is a structural locating member as well as a spring/damper; camber is adjusted at the strut-to-knuckle joint using slotted holes or cam bolts.

On a short-long arm (SLA) suspension, camber is set with shims at the upper control arm and caster with shims at the upper arm pivot.

Spring rate in lb/in increases with larger wire diameter, fewer active coils, or a smaller mean coil diameter.

Ride height must be checked before alignment; sagging springs change camber, caster, and SAI, so alignment set on a sagging vehicle is invalid.

Load-carrying ball joints are checked for axial (vertical) play with the vehicle weight on them; follower ball joints are checked for radial play.

Rubber bushings and pivot bolts must be tightened with the suspension at normal ride height, otherwise the bushing is torsionally preloaded and fails early.

Stabilizer bar links and bushings cause clunk or rattle over bumps; check for play with the suspension loaded and a pry bar.

Worn dampers show cupped tire tread, excess rebound, fluid leaks, and longer stopping distances; a bounce test alone is not a valid pass/fail test.

Air suspension uses height sensors, a compressor, and a valve block; leveling must be recalibrated after component replacement, and leaks are located with a soap solution.

Adjustment order: set tire pressure and ride height first, then caster and camber, and always set toe last because toe changes with camber and caster.

Positive camber tilts the top of the wheel outward, negative tilts it inward; excess negative camber wears the inner tread edge, excess positive wears the outer edge.

Caster is not a tire-wear angle; increasing positive caster (steering axis top rearward) increases steering effort and improves straight-line stability.

Positive toe (toe-in) means the fronts of a tire pair are closer together than the rears; excess toe produces feathered tread wear across the tread face.

Thrust angle is the average rear toe relative to the vehicle centerline; a nonzero thrust angle causes dog tracking and an off-center steering wheel.

Included angle = SAI + camber; a bent knuckle or spindle changes included angle and cannot be corrected by adjustment.

Steering wheel centering is done after toe is set, by adjusting both tie rods equally or repositioning the wheel on the column splines.

Setback is one front wheel displaced rearward of the other; it indicates bent suspension or frame components rather than an adjustment error.

Toe-out on turns (turning angle) is built into the steering arms and cannot be adjusted; a bent steering arm alters it and also skews included angle.

In P225/60R16: 225 mm is section width, 60 is the aspect ratio (sidewall height is 60% of width), R is radial construction, and 16 is rim diameter in inches.

Load index gives maximum load capacity and the speed rating letter gives maximum sustained speed; both must meet or exceed the vehicle tire placard.

Minimum legal tread depth is 2/32 inch (1.6 mm); the tread wear indicators molded into the grooves are set at that same 2/32 inch height.

Positive offset means the mounting face is outboard of the wheel centerline; backspacing is measured from the mounting face to the inner bead flange.

Lug nuts are tightened in a star or crisscross pattern in stages to the specified torque so the wheel seats evenly against the hub.

Static balance corrects imbalance in one plane (up-down hop); dynamic two-plane balance corrects side-to-side rocking; road-force balancing addresses radial force variation.

Direct TPMS sensors contain batteries that typically last 7-10 years; sensor IDs must be registered or relearned after replacement or tire rotation per the service procedure.

Directional tires may only be rotated front-to-back on the same side; asymmetrical tires must keep the sidewall marked 'outside' facing outboard.

Tire conicity produces a steady pull; it is identified by cross-switching the front tires and seeing whether the pull direction reverses.

Vibration that varies with road speed points to wheels, tires, runout, or the driveline; vibration that varies with engine RPM in neutral points to the engine or torque converter.

Shimmy occurring mainly at 50-65 mph most often involves wheel balance, radial or lateral runout, or worn steering and suspension joints.

Clicking or popping from a front corner during turns under acceleration indicates a worn outer CV joint, usually following a torn boot and grease loss.

A wheel bearing growl changes volume when the vehicle is swerved left versus right, because the loaded side changes; confirm with a 12 and 6 o'clock wheel shake.

Torque steer on acceleration in a front-wheel-drive vehicle is affected by unequal halfshaft lengths and angles, and is worsened by worn control arm bushings or engine mounts.

Memory steer, where the vehicle keeps turning after the wheel is released, is caused by binding strut bearings, ball joints, or steering shaft universal joints.

After alignment or ride height changes, steering angle sensor calibration and ADAS camera or radar recalibration may be required by the service procedure.

Subframe or cradle shift changes camber and caster on both sides; check body-to-subframe alignment holes before condemning suspension parts.

Pull diagnosis order: verify tire pressures, cross-swap tires to test conicity, check for brake drag, then measure alignment angles.