negative camber/positive ...
negative camber/positive camber
The Basics: Springs, Anti-Sway Bars and Shocks
A brief suspension primer is in order. Since most AWD cars exhibit a front-weight bias, they tend to understeer and as such need a disproportionately larger amount of rear roll stiffness to help counter this when compared to a typical FR sports car. AWD vehicles require more rear spring and/or rear bar, pretty close to what works well in a FWD car. For serious autocrossing, track days and racing, the standard rear suspension spring rates usually offered by Japanese coilover makers tend to be too soft in proportion to the front, however this remains debatable by many suspension experts. The ratio of front and rear stiffness offered is more appropriate for street driving. Such companies also seem to do the same thing concerning FWD cars. If you're a capable driver participating in many track events, you're better off ordering stiffer rear springs than what's typically offered. For track use, EVOs and DSMs should be fit with slightly stiffer rear springs, while Subarus require fairly equal rates at both ends erring slightly stiffer up front.
Tip 1: Add Negative Camber
Camber is the inward or outward tilt of the tires when viewing them from the front. Positive camber is when the top of the tire tips outward. Negative camber is when the top of the tire tilts inward. A tire must use its contact patch efficiently to generate its maximum grip potential. Thanks to problems like tire distortion and production car-compromised suspension geometry, this rarely happens. When a tire is subjected to side load its sidewalls flex, digging the outside tread into the ground and lifting its inside into the air. If you drive hard, you've probably noticed the outside edge gets chewed up faster than the rest of the tread. As a car rolls into a corner, the chassis roll tilts the tire onto its outside edge, worsening the problem. Keeping the tires flat on the road is the primary reason to add negative camber and combat tread lift. Since AWD cars have a large percentage of weight over the front wheels, they require more negative camber up front when compared to other drivetrain types - about the same amount that a FF sedan needs. Dialing in negative camber helps combat tread lift and wheel tilt. Camber also creates a force that pushes the car inward. This force is called camber thrust and is used to increase cornering abilities since it's much greater on the heavily loaded, outside tires.
SPC Performance also offers...
SPC Performance also offers an optional toe adapter for the FasTrax. The brackets fasten to the FasTrax system, giving users a suitable place to reference toe measurements from. Dialing in toe properly is critical, as improper toe is one of the quickest ways to destroy a new set of tires.
The trick is to add just enough negative camber so the tread stays flat and engaged with the ground under side load and roll. Adding too much negative camber will hurt more than it will help. Excessive negative camber will reduce braking traction, reduce acceleration traction, increase the tendency to tramline (following cracks and grooves in the pavement), increase crown sensitivity (wandering caused by road contour) and affect tire wear (the insides of the tire tread will wear faster with more negative camber if you don't corner hard; conversely, if you constantly corner hard, your tires will wear more evenly and last longer).
Adjusting camber is worth the effort. Optimizing camber for your type of car and driving style can often make a bigger difference in the amount of stick generated than just about any other mod, besides tires.
Vehicle types and driving demands together determine how much negative camber is needed. Aggressive drivers should use more. Those concerned about tire life while commuting should use less. Suspension design also matters. MacPherson strut cars like the WRX/STi, DSM and EVO front suspensions need more negative camber to work well under cornering load; multi-link suspensions like those found on the rear of the DSM and EVO and the Skyline GT-R generally need less negative camber. Softer suspended cars that lean over in turns generally need more negative camber to grip well.