Remember: set the camber first,...
Remember: set the camber first, then the caster, and then the toe, as changes to the camber affect the toe. The alignment shop should already know this, but it doesn't hurt to mention it. We set the caster and camber to Chuck's street alignment suggestions with the Maximum Motorsports plates.
Road Racing
The amount of negative camber on a road-raced car can become aggressive. As much as 3.5 degrees isn't unusual for some tracks. The camber is usually set to what works best at a particular track, and is usually different from side to side to optimize the car. Taking tire temperature, checking tire pressure, and keeping an eye on tire wear will guide toward the best camber setting. On our road-race Mustang, we may change the alignment before every session for a particular track. We pay as much attention to the wear pattern as the tire temperatures. Usually, the alignment that produces the best handling also has the most even tire wear.
The toe is set to toe-out, making the car respond more quickly when turning in for the corners. The amount typically ranges from 1/8 inch overall to as much as 1/4 inch, depending on the track. Excessive toe-out makes the car unstable at speed and darty under braking. It will also increase drag on the straights and increase tire wear. It takes experimentation to find the best setup for a particular track.
For a road racer, caster is increased compared to what a street car has. Any car that is road raced should have the bumpsteer measured and adjusted. Since that takes care of the bumpsteer issue, caster can be set to as much as 8 degrees positive. More positive caster causes more negative camber when you need it. The caster setting affects the camber when the front tires are steered, while the car is cornering-but not when the tires are steered straight ahead. There is a tip-over point at around +4 degrees of caster. Above that amount, the camber becomes more negative on the outside front tire, as it's steered during cornering.
Set the toe by adjusting the...
Set the toe by adjusting the length of the tie rods. This will take some finesse work, as tightening the hardware changes the toe setting. Plan for that and you'll be OK. You're done-take it for a spin.
Drag Racing
In this application, the most important thing is straight-line stability. Everything should be focused on that.
Camber should be set at a minimum, between 0 and -1/2 degree. As the front of the car rises, it will move toward positive.
Caster should be set just as with a street-driven car: increased to a more positive setting than stock, but not enough to cause a bumpsteer problem. Serious competitors realize that even in drag racing, the suspension alignment is as important as anything else. To keep good straight-line stability, drag-race cars should have the bumpsteer measured and adjusted to the minimum amount. When that happens, the caster can be set to as positive as possible, whether it's a Fox or SN-95 chassis.
The toe setting should be slightly toed-in, again to enhance straight-line stability.