When you turn the steering wheel, the inner-wheels will travel in a different radius, than the outer-wheels:



Because of this, the inner-wheel needs to turn more than the outer-wheel, to prevent the tires from scuffing/scrubbing (losing grip).

However, in order to achieve this toe-out on turns, you need to integrate the Ackermann steering geometry. In short, it's basically an imaginary "V" from the steering arms to the dead center of the rear axis as seen in the above 2 photos.

That Ackermann angle is engineered into the vehicle with the OE wheel in mind. When you buy a wider wheel, wheel spacers, or something that changes the offset, your Ackermann angle has also changed. The reason why I started this thread is to see if anyone knew if this made any difference. They way I see it on paper, the wheels are now turning at a different radius than the stock setup, and the Ackermann angle hasn't been compensated. Therefore both wheels should be scrubbing (losing grip) which means understeer and reduced vehicle handling.

The scrub radius is basically the centerline of the wheel relative to the steering axis inclination:



When you change the wheel's offset, you change the scrub radius. Apparently the only thing that this effects is the amount of effort required to turn the wheels, and the car's stability during braking/acceleration.

As for hubcentric spacers, everyone knows that the vehicle's weight is supported by the lug nut bolts right? WRONG! The vehicle's weight actually sits on the hub assembly. There's a round protrusion on the hub where the vehicle's weight is supported, and transferred to the wheel:



When you add wheel spacers, you're pushing the wheel off of the hub, and onto the bolts which CANNOT support a 3000+ pound vehicle. This is why you need hubcentric wheel spacers:



They have that same lip that the hub does so that the vehicle's weight is properly supported. The vehicle now rests on the hub again instead of the wheel bolts, which can break.

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