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The toe angle seems to be the biggest contributor to tire wear and to rolling resistance. (Both from scrubbing the tire against the pavement, I guess.) You can check the toe angle with strings and jack stands. You have to make sure the jack stands are the same distance from the centerline of the car, which is the hard part. (Sometimes just determining what the actual centerline is turns out to be the really hard part!)
After you get the stands set up and string tied to them so that the string is parallel to the centerline, you measure from the string to the rims. A measurement at the front-most part of the rim and the rear-most part of the rim will give you an idea if the wheel is pointing out at the front (toe out) or out at the rear (toe in) or if both measurements are equal, you have zero toe. In general, you want zero toe for lowest rolling resistance, and toe-in for stability. Or toe-out for instability, if you need your car to be unstable for some reason. (Say if you're autocrossing it.)
Whichever way you want to set the toe angles up, there are a few things to remember:
- We're talking small distances here. If the difference between the front and rear of the tire is more than bout 1/8", chances are that is too much toe angle on that wheel!!
- All suspensions have some compliance, and as a result the toe angles will change while you are driving. Driven wheels (front on a FWD car) will tend to pull themselves into more toe-in, while non-driven wheels will tend to get dragged into more toe-out. As the suspension compresses and rebounds, the toe will also change dynamically. (This is called "bump steer".) It may be necessary to compensate for those when setting the toe statically!
- After making changes to the suspension settings, it is a very very good idea to bounce the car up and down and roll it back and forth for everything to settle in. It is even better to drive it around for a little while, but that takes more time.
If you google "DIY alignment", you'll find a lot of information out there on this subject.
-soD
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