Camber, caster, toe, SAI, included angle, and turning radius — what each angle does, what bad numbers cause, and how to read a printout like a chassis engineer.
ANGLE 01 · CAMBER
Positive camber = top of wheel leans out. Negative camber = top leans in. Modern cars run slight negative camber (−0.5° to −1°) for cornering grip. Most read in degrees and minutes.
| Excess negative | Inner edge tire wear · pulls toward more negative side |
| Excess positive | Outer edge wear · pulls toward more positive side |
| Cross-camber > 0.5° | Vehicle pulls toward more-positive side |
ANGLE 02 · CASTER
Positive caster = steering axis tilts toward driver. Provides straight-line stability and self-centering. Most modern cars run +4° to +7°.
| Too little caster | Wandering · poor self-centering · light steering feel |
| Excess caster | Hard steering effort · increased road shock through wheel |
| Cross-caster > 0.5° | Pulls toward side with LESS caster |
ANGLE 03 · TOE
Toe-in = front edges of wheels closer than rear edges. Toe-out = opposite. Most modern alignment specs show 0° to +0.20° total. Measured in degrees, decimal degrees, or inches.
| Excess toe-in | Outer edge feathering · "scrubbed off" tread |
| Excess toe-out | Inner edge feathering · darty steering |
| Unequal toe side-to-side | Steering wheel off-center · vehicle dog-tracks |
ANGLE 04 · SAI
Tilt of the imaginary steering axis from vertical, viewed from the front. SAI is built into the vehicle — it's a diagnostic angle, not adjustable. Combined with camber, it gives you the included angle.
| SAI in spec, camber out | Bent upper strut or knuckle (camber-only fault) |
| SAI out, camber in | Bent lower control arm or cradle |
| SAI and camber both off | Strut tower damage · frame bent |
ANGLE 05 · INCLUDED ANGLE
The sum of SAI and camber. It's the angle between the steering axis and the wheel itself. Used to isolate whether camber problems live in the knuckle or somewhere else.
| Included Angle in spec, camber out | Bent strut or cradle (suspension upstream of knuckle) |
| Included Angle out, camber in | Bent steering knuckle (knuckle itself is the fault) |
ANGLE 06 · TURNING RADIUS
When the wheels are turned, the inside wheel turns sharper than the outside wheel — they trace different radii around a common point. The difference is built in by the steering geometry (Ackermann principle).
| Outside wheel turns sharper than inside | Bent steering arm · damaged rack mounting · crash damage |
| Inside wheel turns sharper than expected | Squealing tires on slow corners · feathered shoulder wear |
| Both sides match | Geometry intact · check elsewhere for tire wear |
Modern alignment racks output a printout with current readings, spec ranges, and total adjustments. Walk through it in this order, every time.
1 · CHECK CASTER FIRST
If caster is out, fix it first — it affects camber readings on most suspension designs. Cross-caster (difference left to right) more than 0.5° will pull the vehicle toward the lower-caster side.
2 · CHECK SAI + INCLUDED ANGLE
Before adjusting camber, look at SAI and IA. If they're out, you have bent parts — adjusting camber will get the number into spec but the vehicle will pull or wear tires anyway. Find and replace the bent knuckle, strut, or control arm first.
3 · SET CAMBER
Cross-camber more than 0.5° pulls the vehicle toward the more-positive side. Target spec center, not the spec edge — split the difference between left and right.
4 · SET TOE LAST
Toe is adjusted after everything else because every other change affects it. Center the steering wheel before setting toe — most racks have a wheel-lock to hold it. Adjust each side equally so the steering wheel stays straight.
5 · DON'T SKIP THE THRUST ANGLE
Thrust angle is the rear-axle direction relative to the vehicle centerline. If it's out, no amount of front-toe adjustment will get the steering wheel centered. Rear toe adjustments may not exist — at that point you're checking for collision damage or worn trailing-arm bushings.
A reading at the edge of spec is still in spec — but it leaves no margin. Bushing wear, suspension settling, or a small collision can push it out within months. Always target spec center on the first alignment. The customer doesn't come back in 6 months for a re-alignment.
If SAI is out, your camber adjustment is masking a bent suspension component. Numbers will look right on the printout, but the vehicle will still wear tires unevenly and pull. Always check SAI and IA before condemning a camber adjustment as "good." Bent struts and knuckles are the answer, not turn the camber bolt.
If you set toe with the steering wheel off-center, the vehicle drives straight but the steering wheel is crooked. Customer comes back complaining. Always center the steering wheel with the rack's lock tool, then adjust toe equally on both tie rods.
Half of front-end "pull" complaints are actually rear thrust angle problems. The rear axle is dog-tracking and the front wheels are compensating to keep the vehicle straight. Check the thrust angle on every alignment, even if there are no rear-toe adjustments — sometimes you find trailing-arm bushings, sagging springs, or unreported collision damage.
Print this. Stick it inside your toolbox lid.
ADJUSTMENT ORDER
CASTER → SAI/IA check → CAMBER → THRUST ANGLE → TOE LAST
PULL DIRECTION
| Cross-camber | Pulls toward MORE-POSITIVE side |
| Cross-caster | Pulls toward LESS caster side |
| Rear thrust angle | Pulls toward thrust direction |
TIRE WEAR FROM ALIGNMENT
| Inner edge wear | Negative camber · toe-out |
| Outer edge wear | Positive camber · toe-in |
| Center wear | Overinflation (not alignment) |
| Both shoulders | Underinflation (not alignment) |
| Feathering | Toe error |