Basic suspension geometry can make major changes to how your car or truck handles, and even save you money.
A good alignment will make your car handle, brake, and accelerate better for very little investment. You'll even save money by reducing tire wear with a simple correction to the camber and toe.
Camber is a measurement of the centerline of your wheel/tire relative to the road surface. It is expressed in degrees and greatly affects the dynamics of the car.
Negative camber is when the top of the tire tucks inwards. For a road going car you typically want to maintain a slight amount of negative camber (1 2 Degrees) to improve road handling. Camber improves handling by allowing the tire to apply even loading when the body rolls going into a corner. Without negative camber the tire would load the outer portion of the tire which would reduce overall grip.
Downsides to negative camber are increased inner tire wear since during normal driving conditions the tire will apply more load to that portion of the tire. Large amounts of static camber will also generally reduce overall grip during braking and straight-line acceleration.
Race teams will know how much camber to dial into their car from thermal tire data and driver feedback. At proper camber settings the tire will exhibit stable and symmetrical temperatures across the tire surface during cornering. Excessive heating on the inner or outer third of the tire can be indicative of improper camber angle.
Positive camber is when the top of the tire extends outward, and the base of the tire tucks inwards. This is rarely ever seen on a road car since it will reduce road handling capability. In special situations, such as NASCAR, positive camber will be applied to handle heavy amounts of track embankment. If you are running a positive camber figure on your street car then its highly recommended that you inspect your suspension for damage and/or adjust the camber to a slight negative figure.
Caster is the measure of how far forward or behind the steering axis is to the verticle axis, viewed from the side. An example of caster in action is the front wheels on a shopping cart. They run a large amount of positive caster to make the cart track straight without wandering. However, the method that the cart uses (displacement caster) is different than how your car develops its caster angle (angled pivot), but the effect is the same.
Positive caster is when the steering axis is in front of the verticle. In a road car, this would mean that the top of the coilover would be pushed towards the rear of the car. Positive caster creates a lot of align torque (the force that straightens the steering wheel when you go forward) which improves straight line stability of the car. Due to the geometry of positive caster it also will increase negative camber gain (a good thing) when turning. As you increase positive caster the steering will get heavier also, but with modern power steering systems this is rarely a problem. Generally you want as much positive caster as you can reasonably get so long as the car is equipped with power steering.
Negative caster is when the steering axis is behind the vertical. This is generally only found on older vehicles due to tire technology, chassis dynamics, and other reasons. Modern vehicles do not use negative caster. It will lighten the steering effort but also increases the tendency for the car to wander down the road.
Regardless of what caster setting you use, make sure that your caster is symmetrical. Running a different amount of caster on one side will cause the car to pull towards the side with less caster.
Toe is the measure of how far inward or outward the leading edge of the tire is facing, when viewed from the top. Toe is measured in degrees and is generally a fraction of a whole degree. It has a large effect on how the car reacts to steering inputs as well as on tire wear. Aggressive toe angle will cause the tire to develop feathering across its surface.
Toe-in is when the leading part of the tire is turned inwards towards the center of the car. This makes the tires want to push inward, which acts to improve straight line stability of the car as its traveling down the road, particularly at high speed (highway).
Toe-out is when the leading part of the tire is turned outwards away from the center of the car. This makes the tires want to separate from each other. This improves turn-in response considerably but again, at the cost of tire wear. Running toe-out in the rear is generally not recommended since it will make the car want to pivot (oversteer) at all steering angles, but in the right setup it can help (auto-x / technical tracks).
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