Introduction
Camber, Toe and Caster angles are one of the mist important changes we make to a car to adjust corner grip levels, manage tyre wear, braking effectiveness and the amount of steering feedback we get through the wheel. Camber and toe are affected by ride height changes as we discussed in the ride height and aero balance section. In addition, changing the caster angle in most cars will affect the camber angle as well. This is the nature of most suspension geometries in a racing car.
Camber
Camber is the vertical angle of the wheel relative to the track surface. We usually tune camber angles to optimize the outside tyre’s contact patch when the car is turning. In most of the cases, race cars use negative camber so for example in a corner we need the outside tyres to have the most contact patch as they are the ones with the most load. You can see this effect in the illustration below.
This adds more grip to the tyres and therefore we can carry more speed at the apex of the corner. Keep in mind that having too much negative camber will have effects on braking performance in a straight line by locking up the wheels and more tyre wear especially in the rear tyres. Too much negative camber in the front tyres might also cause snap understeer causing the car to drift outwards. Similar effect can happen in straight line situations when braking and exiting. Too much negative camber in the rear tyres might also cause snap exit oversteer.
So what do we do to find the balance? The best way to test camber settings especially for endurance racing where the stints are long, is to test full stints and monitor the tyre wear during and at the end of the stint. In addition having the car reactions mentioned above with too much camber applied is a sign that we need to tone down the camber angle to eliminate these problems. Below you can find the effects of changing the camber angle.
Note: These changes are always for a negative camber
Toe
Toe is the angle of the wheels relative to the track surface if we inspect the car from the top. The reason we change the toe angle is that by having the front or rear tyres work against each other, keeps the car stable over imperfections on the track surface which improves stability and drive-ability. There are 3 toe descriptions: toe IN, toe OUT and ZERO toe. You can see the illustration of these descriptions in the image below.
Most race cars have a negative toe angle (toe OUT) in the front axle and a positive toe angle (toe IN) in the rear. Having a negative toe or a toe OUT in the front helps the car’s entry into the corner by increasing the responsiveness of the initial turn of the wheel. Having a positive toe or a toe IN in the rear tyres helps the car’s rear grip and overall stability in the middle of the corner. In some extreme cases, some setups are build with having a small negative toe in the rear tyres to have a rapid transition of oversteer when the tyre grip limit is reached. This is done to decrease significant amounts of understeer in unique situations.
Keep in mind that having a large toe angles have an effect on the straight line speed of the car as we have the wheels pushing against each other. Below you can find the effects of changing the toe angles in the car.
Caster
Caster angle is the angle between the tyres and the steering axis when looking at the car from the side. Caster angle is usually changed to improve the amount of feedback that the driver wants to feel. Mostly this is a driver preference but having too much caster angle detriments stability in corner exits and high speed corners.
Keep in mind that changing the caster angle will often change the camber angle in the front tyres as well. Before making any changes to the caster angle, make a note of the front camber angles as well.
Tutorial tip
In certain tracks, the Ferrari 488 GT3 uses a small negative toe angle on the rear!