In car handling, slip angle is the angle between a rolling wheel's actual direction of travel and the direction towards which it is pointing (i.e., the angle of the vector sum of wheel translational velocity vX and sideslip velocity vY). This slip angle results in a force perpendicular to the wheel's direction of travel -- the cornering force. This cornering force increases approximately linearly for the first few degrees of slip angle, then increases non-linearly to a maximum before beginning to decrease.

what this means in English for you and me... You turn into a corner, a slight amount of steering wheel input and the slip angle is near zero. so the car turns faster and faster with more steering wheel input. until eventually you exceed the slip angle your tires operate at then you begin to loose sideways (cornering) force.. in addition as your wheels near 45 degrees a good portion of that sideways cornering force becomes braking force pushing backward against the forward progress of the car. (this is often called "scrubbing speed" almost never a good thing when trying to set a lap time) and turns your momentum into heat and tire dust.

Just like when accelerating or braking the tire generates it's optimum force (Gription) when it's sliding but only a small percentage of it's overall movement.

This is where things start getting fun for the tuner since you can adjust the optimum slip angle with alignment, Tire loading (spring rate or sway bars)

A non-zero slip angle arises because of deformation in the tire carcass and tread. As the tire rotates, the friction between the contact patch and the road result in individual tread 'elements' (infinitely small sections of tread) remaining stationary with respect to the road. If a side-slip velocity u is introduced, the contact patch will be deformed. As a tread element enters the contact patch the friction between road and tire means that the tread element remains stationary, yet the tire continues to move laterally. This means that the tread element will be ‘deflected’ sideways. In reality it is the tire/wheel that is being deflected away from the stationary tread element, but convention is for the co-ordinate system to be fixed around the wheel mid-plane.
As the tread element moves through the contact patch it will be deflected further from the wheel mid-plane: (and as you can guess a slick tire does not suffer this deformation)




This deflection gives rise to the slip angle, and to the cornering force.
Because the forces exerted on the wheels by the weight of the vehicle are not distributed equally, the slip angles of each tire will be different. The ratios between the slip angles will determine the vehicle's behavior in a given turn. If the ratio of front to rear slip angles is greater than 1:1, the vehicle will tend to understeer, while a ratio of less than 1:1 will produce oversteer. Actual instantaneous slip angles depend on many factors, including the condition of the road surface, but a vehicle's suspension can be designed to promote specific dynamic characteristics. A principal means of adjusting developed slip angles is to alter the relative roll couple (the rate at which weight transfers from the inside to the outside wheel in a turn) front to rear by varying the relative amount of front and rear lateral load transfer. This can be achieved by modifying the height of the Roll centers, or by adjusting roll stiffness, either through suspension changes or the addition of an anti-roll bar.

Now I can include all the math it takes to calculate these items, but for our purposes it's not required, just understand that whenever trying to make a suspension behave in a desired way the slip angle of the tires must always be taken into account. since exceeding the design of your tire will result in slower lap times and make your tuning much harder.

A good quote I was reminded about is "if your tire is growling you are close, if your tire is howling you've exceeded the slip angle" Back off a bit. we will also discuss later how driving style, by allowing the car to load up the tires properly, and using the dynamic weight shift of the vehicle. you will get increased performance out of the same exact car.