The elements that suggest any settings are reliant on that type of drive the car has, rear wheel drive will push the relaxed front wheels away from the cars centre line or toe out, front wheel drive since they are pulling the car, will pull the toward the centre line or toe in , both situations are in a driven state so static (not in motion) settings are calculated for the wheels to achieve the desired zero setting.
All this done there is still one more element to consider, and that is rolling resistance, tyre contact be it front or rear wheel drive will encounter the resistance of friction and this will inevitability put any setting in dispute.
Since all, or any variable cannot possibly be considered finite then the front wheels alignment setting should only be perceived as a suggestion,
The front wheel alignment setting is going to be unique to you and your car, the wear pattern and compensation will need to be read, and a good technician should use the tolerances available from the manufacture as fine tuning (not exactly rocket science),
As an instructor I would never recommend just measuring and adjusting the front wheel alignment because all references for front toe emanates from the rear, if you do not know where the back is, what right do you have to set the front,
Nevertheless front wheel alignment must be checked, and I recommend every three months, seems a bit frequent, but the best time to get the alignment checked is when you do not have a problem that way you should not have one, and since most centres test for free then why not?
One of the most commonly asked questions I get is why does it go wrong? most people believe road humps are responsible, this is not the case in any standard situation, as the car progresses onto the hump the suspension is more than able to absorb it since it’s at a reasonable speed as it is when parking, the kerb only acts as wheel grinding guide to the fact that you are there,
The culprit of most geometry misalignment is the pot hole, 30 miles per hour and 50 Milliseconds freeze the wheels momentum relative to cars the inertia, this will stretch and compress the frames rigidity, albeit in small amounts, the modern car is not as forgiving as cars used to be, so even very small progressive impacts spoil the geometry, the reason for the frequent alignment checks are these small changes, The attitude of the modern cars alignment nowadays, is more or less indiscernible to the driver until the tyres have worn out ….
This picture demonstrates typical alignment wear, the gradient suggests a toe in tendency allowing the road to scrub laterally across the tyre from left to right, increasing friction from the dominant leading edge on the outside,