I am porting this from and another forum, but it has some very good information.
Understanding the meaning of each part
Toe is the relationship of the tires as viewed from directly above (or directly below, as the street sees them). 0 toe will have the tires absolutely parallel when rolling down the street. Most factory alignments use toe in, the tires are usually pointed in ever so slightly (usually 1/16th of an inch, give or take). With toe in, the steering needs to be turned enough to cause both tires to "point" the direction you want the car to go (as you turn the wheel, one wheel will remain pointed straight ahead while the other begins the turn....turn the wheel a little more and both wheels begin to make the turn....toe in tends to add stability to a vehicle....it makes the car less "twitchy"). With 0 toe, when the wheel starts to turn, the car will begin to turn as well, both wheels begin the turn together. 0 toe tends to make a car much more willing to initiate a turn. Toe out will do the same as 0 toe, but it goes a step farther...since the wheels are already pointed slightly out, the car is already "trying" to turn, it makes a car even less stable and more willing to turn (some cars will become very "twitchy" or "nervous").
Camber is the tilt of the tires as viewed from directly in front of the vehicle (if you take 2 tires and stand them up in your garage and lay on the floor in front of them, they will likely be parallel, both standing vertically, which would be 0 camber). Negative camber is when the tops of the tires are closer together than the bottom of the tires, positive camber is when the tires are closer together at the bottom than the top (negative camber is / \, positive camber is \ / as the tires are viewed from the front) As a car begins to take a turn, the forces acting on a car begin to cause "body roll", during body roll, the front tires will begin to change the way the tire sits on the ground. As the body rolls, the contact patch on the road may be reduced (as the tire tilts away from the ground), to combat this, we add negative camber to the front suspension. Negative camber will help reduce the tendency to wear the outside edge of tires on cars that are driven hard through the corners. Negative camber will also help keep the contact patch of the tire flat on the ground during body roll. If you increase negative camber, you will begin to sear the inside edges of the tires when driving around (non-aggressively), since there is slightly more load on the inside edge than there is on the outside edge.
The best way to describe castor is to look at a front wheel on a shopping cart, the carts front wheels stay straight due to castor. Castor is the angle of the point that the spindle rotates on when you turn the wheel. It is not straight up and down like you may think. The tire actually turns on a "tilted" axis. If you turn your wheels all the way to one side and look at them from in front of the car, you'll see that one is tilted in, and the other is tilted the same way (\\ or //), Now, if we have negative camber (with the wheels straight), how did we get negative on one side and positive on the other? That is castor at work. As you move the axis that the steering pivots on, you can get the steering to add negative camber when the wheel is turned. More or less castor will change the ultimate amount of negative camber "seen" by the road surface. It is a delicate balancing act....too much castor, you will have very "heavy" steering, too little and you'll lose cornering grip.
Setting up for an alignment your way and best recommendations for our cars
For street use, anything from -.5 to -1.5 camber is acceptable. Meaning, no evil handling characteristics, just progressively more grip as you head towards the -1.5 number (not all cars can get that high, I ran out of adjustment at -1.3). So, for street use (mild) we usually recommend -.5 to -.7 camber (as high as -1.0 for an "aggressive" street setup, people autocross on -1.3). We suggest a -.7 as a very good compromise for even better tire wear.
For street use, 0 toe is good. Toe out makes the car more responsive (it wants to turn), because toe out makes it slightly unstable (not bad at all, think of balancing a ruler, standing straight up on your hand, it naturally wants to fall over, my car naturally wants to turn). 0 toe is a good compromise for street use. It makes the car slightly more responsive than it is now and it is still extremely stable.
For street use we recommend +4.5, it keeps the steering from being too heavy and allows for a decent amount of negative camber while turning (go turn your wheels all the way to one side, notice that they are both "tilted" the same way, that's castor at work). We would not advise going lower than 4.3 nor higher than 5.0 and we really prefer 4.5 (as do many people). At 4.5 you'll have a stock steering feel, not too light and not heavier.
Mild Street Alignment:
Slightly More Aggressive:
Even More Aggressive:
The Full Race Setup
1/32" to 3/32" Toe Out
-1.3 to -1.5 Camber (whatever max is after the castor is set at 4.5)
Each step will be slightly worse on tire wear and will be slightly more responsive and make more total grip than the one before it. For street use, any of the first 3 work great. If you really like to beat on it around cloverleaf type exit ramps, we suggest that you go with the 3rd setup. If you are just looking for something for a cruiser and weekend driver, the 1st or 2nd are both good setup. The 4th setup will make the car very responsive, but it may hunt on uneven pavement and be "darty" at times.
The Above information is just to give you an example what going aggressive with a setup means. Here are the Ideal specs for OEM setup:
Wheel Alignment Specifications
•Camber (Cross Tolerance)
-1.40 to -0.40 Degrees
•Caster (Cross Tolerance)
2.50 to 3.50 Degrees
-3.50 to +3.50 Degrees
-0.10 to +0.30 Degrees
•Camber (Cross Tolerance)
-1.40 to -0.40 Degrees
-0.15 to +0.15 Degrees
-0.14 to +0.26 Degrees