Why toe needs the tire diameter
Toe in degrees is an angle; toe in mm or inches is a linear measurement taken across the tire tread. Converting between them is pure trigonometry, but the lever arm is the tire diameter:
toe (degrees) = atan(toe mm ÷ tire diameter mm)
The same 3 mm of toe is 0.27° on a 630 mm tire but 0.34° on a 500 mm trailer tire — which is why a spec in degrees and a spec in mm only agree for one tire size. Always convert using your measured diameter.
Reading camber specs
Workshop manuals love degrees-and-minutes: −1°30′ is −1.5 decimal degrees (one degree = 60 minutes). The slope forms — mm/m or percent — describe the same angle as a rise over a one-metre run: mm/m = tan(angle) × 1000. A degree of camber is about 17.5 mm/m.
Typical street ballparks
- Toe: ~0.05–0.15° total toe-in per axle (a few mm), toe-out only for specific motorsport setups.
- Camber: −0.5° to −1.5° street; −2° to −4° for track work with the tires to use it.
- Caster: +3° to +8° — more gives stability and camber gain in turns, at the cost of steering effort.
FAQ
Is toe-in measured per wheel or total?
Both conventions exist — check your manual. Factory specs are often total toe for the axle (the sum of both wheels), while alignment machines may show per-wheel values. This tool labels which is which; total = 2 × per-wheel for equal angles.
How do I measure toe with string at home?
Run string around all four tires at hub height, square it to the car, then measure the gap front and rear of each tire. The difference, at the tire's diameter, converts to degrees here.
Why does negative camber help cornering?
Body roll tilts the outside wheel positive in a corner. Starting negative keeps the outside tire's contact patch flat at roll, using the full tread width. Too much just wears the inside edge on the street.