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Let's say you want total toe in 1mm which is 0,5mm per wheel.
If you have 16'' wheels, the diameter of the wheel is 16 times 25.4 mm = 406.4 mm. Calculate the angle of the wheel by taking the arc tangent of 0.5 divided by 406.4, this is 0.0705 degrees and in minutes 4.2 ( 0°04'). It’s about the same for 17'' wheels.
Hope this helps you.
Surely you need to use the radius of the wheel, not the diameter, as the wheel pivots approximately around an axis through its vertical centre line on the hub, not from the back edge of the wheel.
Although even this isn't strictly true as the wheel pivots on a arc away from the centre line of the suspension strut, but at the moment I can't remenber the term used to describe this.
So you would use 203.2mm as the radius giving a greater angle than that that you have stated.
I am not certain if my maths is correct, but with an arc of 0.5mm and a radius of 203.2mm it gives an angle of 0.14 degrees.
So you would need a combined angle of 0.28 degrees to give 0.5mm toe in per wheel.
Thanks a lot everyone. Funny, but all the elignment equipement here uses degrees instead of mm or minutes/seconds. Another thing, when you start doing the alignment, after choosing the car make and the model you usually enter the wheels size. After the alignment is done, when you get the results, they're usually in mm.... So, this means the programs automatically converts degrees to mm for the chosen wheel size. Isn't that weird?
The math is all terriffic and everything, but you're forgetting to incorproate the additional size of the tire. The rims may be 16", but the extra 2 1/2" radius or so of rubber I imagine would make a difference. That's an extra 5" to your wheel diameter. So technically, wouldn't you begin measuring from 21", then converting?