Performance and Custom Wheel Alignment Set-up
Performance street/track cars will require far different alignment specs when compared to your daily driver Prius. After adding any performance suspension upgrade such as springs/shocks, sway bars etc. or a set of “sticky” performance tires a proper alignment set-up is crucial in order to get the most out of these modifications.
“Dales Auto Service has customers from Vancouver, Victoria to Kamloops, Kelowna and all points between to have their modified vehicles set-up and aligned properly.”
Dales Auto Service has alignment technicians who have participated in High Performance Driving Events(HPDE) and have extensive knowledge in vehicle alignment set-up.
Here is some info related to aggressive/track alignment
Toe is whether the front points of the wheels on the same axle are closer together (positive toe) or further apart (negative toe) than the rear points of the same wheels, when viewed from above.
A car with zero toe has the wheels exactly parallel to each other. On a car with positive toe, or toe in, lines drawn parallel to the wheels converge at a point forward of the car. On a car with negative toe, or toe out, the lines diverge forward of the car.
On a road course toe primarily affects eagerness of the car to turn. A car with negative front toe will change direction more easily than a car with positive front toe. A car with negative rear toe will want to rotate into turns. Lower horsepower cars with negative rear toe and higher horsepower cars with zero rear toe will also want to rotate under throttle when exiting turns.
The second effect of toe is drag on the straights. Any positive or negative toe produces more drag than zero toe. [On the street, the effects of the drag outweigh rotational effects of toe, which is why alignment shops frequently would say that toe is the most important parameter to be correctly set for even tire wear.]
Road course cars tend to run zero toe in the front to eliminate drag on the straights, and achieve desired over-steer or under-steer characteristics via other means (primarily via camber and spring/sway bar rates).
Lower horsepower cars tend to use zero toe in the rear, for the same drag reduction reason. Higher horsepower cars may run positive rear toe to avoid unwanted rotation under throttle when exiting corners.
Camber is whether the top points of the wheels are facing inward (negative camber) or outward (positive camber), when viewed from the front.
Camber controls the size of tire contact patch on the respective wheel. Usual car suspension designs result in the outside wheel gaining positive camber in a corner; the harder the car turns, the greater the camber gain. If the car has zero camber standing still (or driving in a straight line), the size of tire contact patch is greatest when the car is not cornering and smallest when the car is cornering. As most cars are limited by grip in corners, setting camber to negative when the car is standing still results in the tires becoming more vertical in the corners, thus increasing the size of contact patch when it is most needed.
Too much negative camber results in compromised tire contact patch under braking and acceleration. Usually this first manifests in uneven tire wear, with inside edges wearing much quicker than the rest of the tire. Optimal camber setting for the front axle depends on how hard the driver corners vs how hard they brake. More advanced drivers tend to corner harder and brake less and therefore are able to effectively utilize more camber on the front wheels. Less experienced drivers who do not corner as hard will want less front camber.
Having too much negative camber in the rear can produce over-steer under throttle when exiting corners in higher horsepower cars, although chances are tire wear will be an issue before this happens. Having insufficient negative camber in the rear may produce over-steer on corner entry.
Generally speaking, street cars run close to zero camber. A “spirited driving” or combination street/track setting would be about -1 to -1.5 degrees of camber. A car that is mostly driven on a track would have -2 to -3 degrees of camber. Camber over -3 degrees is generally seen only in dedicated track machinery.
If the rest of the car/suspension is neutral, having front camber more negative than rear will produce an over-steering car, and having rear camber more negative than front will produce an under-steering car. In a car that is not otherwise neutral, camber can be used to tune over-steer/under-steer behavior.
Caster is whether the bottom of the suspension is forward of the top of the suspension (positive caster) or rearward (negative caster). Usually cars have positive caster, the question is only how much of it. Caster only applies to the front (steered) axle.
Most of the discussion around caster centers on steering effort. In cars where caster helps avoid positive camber gain in corners, it makes sense to run maximum caster possible.
What You Can Adjust
Depending on your car, you may not be able to adjust all of the parameters. For example, cars with solid rear axles generally cannot adjust rear camber. Many cars require aftermarket camber plates to adjust front camber. Aftermarket control arms are frequently offered to allow adjustment of toe and camber on all corners of a car. Research what adjustments are possible on your vehicle.
Road race cars usually are set up with a touch of under-steer. Under-steer rather than over-steer is important so that the car can accelerate out of corners; an over-steering car will tend to enter a drift under power which will result in the driver lifting to keep the car on pavement. This under-steering tendency however is very slight.
With most production cars set up to strongly under-steer from the factory, many track alignment settings are designed to move the cars closer to neutral handling, by making it over-steer more than street settings would. In cases when other suspension components are changed in such a way that the car over-steers (such as installing a huge rear sway bar), alignment can be used to make the car understeer more.
The following will produce a (more) over-steering car:
- Running front camber more negative than rear camber.
- Running rear toe more out.
- Running front toe more out.
Because nonzero toe scrubs speed on the straights, it is usually not desired. Therefore the balance is typically obtained by appropriately setting the difference between front and rear camber.
Many if not most track-only cars have front camber more negative than rear. In contrast, virtually all street cars have more rear camber than front, to maintain under-steer.