Grid Plate Converter
Set the laser line for any wheelbase
A grid plate is graduated for one wheelbase. Put a different car on it and its printed numbers no longer read toe correctly. Enter the plate, the car and the toe you want, and read off where to set the laser line for each wheel.
Your grid plate
Your vehicle
Toe you want, per wheel
Why the plate needs converting
The laser is projected over the car's wheelbase, not the plate's. The same toe throws the line further on a longer car and less on a shorter one, so a plate graduated for one wheelbase reads high or low on any other.
Toe is an angle
A figure in millimeters is a chord across the wheel. One millimeter on an 18 inch wheel is 0.125 degrees; the same millimeter on a 20 inch wheel is 0.113 degrees. That is why the plate and the car each carry a wheel diameter, and why a plate printed in minutes or degrees needs none.
laser position = toe × (car ÷ plate wheelbase) × (plate ÷ car wheel diameter)
