This is how I did it, using a piece of aluminum on the wheel and my phone's angle finder:

From Formula Magazine:

1. Turn wheel 15 degree left of center and take a camber reading.

2. Turn the wheel 15 degrees right of center and take acamber reading.

(You can make a 30 degree chalk line on the floor)

3. Multiply the difference x 2 and that is your castor.

4. When turning from outside to inside a neg camber change equals positive castor. i.e. a change from zero to -1 x 2= a 2 deg pos. castor.


From Performance Marketing Camber Gage:

1. Turn 20 degrees left of center and take a camber reading.

2. Turn 20 degrees right of center and take a camber reading.

3. Take the difference and multiply by 1.5, that is your castor. i.e. left reading +1, right reading +4. Difference =3 x 1.5 = 4.5 deg positive castor.

I confirmed both these ways work using my truck. I lowered it, then had it aligned, then I checked the caster myself in my garage.