Originally Posted By: CapriRacer
Wow. So much to comment on.
First, US cars in the 70's and 80's were dealing with the changeover to radial tires. Radial tires require a different setup than the old bias tires did. Radial tires are less sensitive to camber changes, but more sensitive to toe in.
Second, tires of that era were also changing fairly rapidly. The early radial tires had a very pronounced adhesion break off point. Unlike bias tires, where as you approach the limit of adhesion, the steering input greatly flattens out, the radial tires of the era peaked pretty sharply and small steering inputs were required to stay there. It was very easy to overdo it and lose control. There was a lot of work done to design this out.
And third, car manufacturers and tire manufacturers didn't have a good handle on what tolerances produced good handling and avoided pull and drift issues. One of the things the Japanese vehicle manufacturers quickly learned was how to optimize conflicting priorities. They certainly did a better job than the US car manufacturers. As a result, their cars felt more precise.
Certainly the use of rack and pinion steering helped in that regard and the US car manufacturers were somewhat slow to adopt this.
So I don't think this is so much the alignment values, as much as it is the suspension design.
And commenting on Eljefino's post about the darty Vibe. Toe out will do what he described - and since the allowable tolerance for toe is so wide, it is quite possible for the alignment tech to think things are OK.
Plus, there is a thing called P-Rat (Plysteer - Residual Alignment Torque.) Plysteer is the property a tire has that constantly pushes sideways. It is a characteristic of the tire design and all tires have it to some extent. It is different than conicity, in that reversing the tire reverses conicity, but not ply steer - and concity varies from individual tire to individual tire, where P-Rat is pretty constant for a given make and model.
Plysteer and Residual Alignmment Torque are different ways to looking at the same thing. Many vehicle manufacturers specify an upper limit to minimize drift and pull issues.
Because of this, tire manufacturers should pay attention to P-Rat, but Cooper (who doesn't supply tires to any vehicle manufacturer) may not realize the importance and therefore, not try to control it.
I remember my grandfather being told back then by a tire "vendor" (who didn't have a radial in the size he needed) that "Ya CAN'T have radial tires if you've had a heart attack". I put hundreds of thousands of miles on my Toyota products, BUT I NEVER buy cheap tires. Some of the cheap ones may be good, but I stick to Conti, BGF/Michelin, and
Yoki.