Originally posted by: Pacfanweb
I'm going to provide a very simple, visual explanation of what the different parts of an alignment are, since lots of folks really don't understand:
Toe: Look down at your feet. Rotate your toes inward, like being pigeon-toed. When your wheels do that, that's being "toed in". Opposite is "toed out". Most cars' alignment specs will have the wheels VERY slightly toed in, as the rolling force of the car and the little bit of slop in the components will let the toe move slightly, which will let the wheels be straight when moving.
Camber: \ / <--Looking at your tires from in front of the car. You wouldn't want them sitting like that. They should be basically straight up and down. Tires with camber like those symbols would wear the outside edge horribly.
Caster: Picture the raked front end of a chopper, vs a dirt bike. This is caster. You don't want one side to be drastically different from the other. Can cause weird handling characteristics.
All these specs work in conjunction with each other. There is some tolerance in each spec...meaning there isn't just "one" number to set each one on and it's right.
Sometimes a certain vehicle might need to be to the negative side of the camber spec to not wear the tires. Or might need to be toed in more on one side to keep from pulling.
This is where a "good" front end man comes in very handy, as opposed to someone who just sets all the specs in the middle of the range and lets it go.
You've got it (as usual), but because I can't resist going into more detail:
Caster: Usually combined with "trail". Larger caster angles make the steering heavier, but also improve stability as well as increasing the camber gain during cornering, which is positive for handling.
Toe: Actually has more impact on edge wear than camber. Toe-out increases steering response, but also makes the car more twitchy, sacrificing straight-line stability. Excessive toe causes more issues with tire wear than does camber. Most cases of tire edge wear are from incorrect toe and not from camber issues.
Camber: Positive camber (tire leans outward, away from the car) is rarely good. Negative camber (tire leans inward, towards the car) has benefits for cornering as it counteracts the effects of cornering forces on the outside tires. Most cars have very slight negative camber, both to help in cornering and also because having some camber (regardless of whether it is positive or negative) on the steering axle will result in lighter steering effort.
A more detailed explanation can be found
here.
ZV