OK, I am going to explain to folks about camber and toe and how you can get even tire wear from severe camber settings.
If you've watched any of the Formula 1 races, they sometimes have a thermal imaging camera pointed at the tires. If you watch carefully, when the vehicle is going around a corner, the outside tire (the one doing most of the cornering) has a very even heat signature across the face of the tread. If you look at the other tire, you'll notice it doesn't.
I found a video:
http://www.youtube.com/watch?v=FHC_nZzRBdk
Since most tire wear occurs in the cornering mode, if the outside tire is generating even heat, it is also generating even wear. By the same token, the inner tire (which isn't being evenly heated) develops uneven wear side to side.
- BUT -
The difference in wear rate is astonishing. The inside tire doesn't wear much if the Akerman is the way it is supposed to be (which is usually a problem with street cars). But I'll bet BMW has designed their cars for proper Akerman for hard cornering. (and a side bit is that having too much Akerman is not as bad for tire wear as having too little, however, the cornering feel with a car with too much Akerman is horrible. Just ask me about my van.)
What is Akerman? It is the change in toe as the steering wheel is turned - and typically, street cars need more toe out as they corner than when they are going straight ahead. Think about how the outer tire has to traverse a larger diameter circle, so the inside tire has to be pointed more towards the inside of the turn.
- BUT -
As the cornering force gets higher, the tires have to develop more of a slip angle, and the amount of toe out needed (Akerman) decreases.
So hard cornering in a car not designed for hard cornering results in the inside tire (relative to the turn) being dragged around the corner - and typically, this tire is also cambered the wrong way, and the inside tire wears more.
So now let's imagine what happens if the toe is not set to spec AND there is a high camber setting. When going straight ahead, the tires are being dragged ever so slightly sideways and they aren't wearing evenly. And the worse the toe is, the worse the wear is. The toe acts like a multiplier.
So even a vehicle with high camber can get even tire wear
IF the toe is right. But for every little bit of wrong toe, the effect on wear is worse.
BMW's are known to us in the tire industry as having tire wear issues - but BMW also has the tightest toe tolerance. So while a lot of BMW's don't have wear issues, when they do, they can be quite bad. Unfortunately, many other vehicle manufacturers are using high camber settings and those vehicles are experiencing uneven wear.
