Quote:
Originally Posted by asphaltgambler
So..... I've performed alignments since 1981 professionally. I've used just about every type / brand of equipment and aligned just about everything that would fit on the rack. Further, I've studied this in depth and have attended a lot of training courses over the years. To the point that I taught other technicians 'the rope's' of the business of aligning vehicles. My specialty was problem vehicles that had been to other shops and end result was not satisfactory-or-where vehicles were heavily modified, like a 4x4 truck that was lifted with tall tires, which throws everything off from the manufacturer's original engineering of all the planes of angles working in unison. Specifically steering axis inclination along with axle centerline ( height) point of intersection with the center of the tire tread as it meets the road.
While the summation of this part of my career may or may not qualify me as an expert, at least possibly very experienced. One thing to remember is that when the vehicle is on the rack, all 4 wheels/ tires are sitting on 'floating' plates that allow the suspension to settle naturally.
Remember that the tire wear you see is a direct result of 1 or more angles out of spec, it is a reflection of what is wrong with the settings.
Installing new tires w/o changing any mechanical settings will yield the exact same readings/ measurements as before as the vehicle is sitting on floating plates on the rack.
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Have to agree to disagree with that last part.. I'm in the same boat though. Professional ASE Master Tech and have been wrenching since 1982.. (you got me beat by one year..lol.) I've also been to numerous classes etc and then taught at the manufacturer level for many years...etc.
I agree about the floating plates obviously as that accounts for the suspension to settle etc, but that doesnt account for a tire that is not sitting flat/straight/true because of wear. Even with the suspension settled, if the inside of your tire has no tread and the outside is full (for whatever reason) then the entire wheel is tilted inward, even with the suspension settled, - alignment angles with it. So if you align the car in that situation, when you put new tires on later, your angles will be incorrect...
It is rather diffcult to try to explain this over text!! I do remember watching a training video on this exact thing WAY back when though and I guess it just stuck with me..