Game Development Reference
If the front wheels slide, the car understeers and the arc is larger than the driver intended.
This is commonly caused by traveling too fast through a corner and trying to take the
corner too tightly. However, if the driver breaks hard or even just lets off the gas, there
will be a weight shift forward. This will keep the forward wheels from slipping but if
too aggressive will cause the rear wheels to slip as weight is transferred away from them.
This causes the car to turn more than the driver intended, and can even result in a spin.
These two conditions limit the speed at which a car can complete a turn and also the
amount of deceleration the car can handle once the turn is initiated.
To increase the limit speed, v limit , we must increase the normal force. We could do so by
increasing the car's mass, but this would have negative effects on the car's ability to
accelerate or decelerate. A better solution is the use of aerodynamic features to create
what is called downforce . You may have seen racecars or even street cars with large wing-
like features called spoilers on their trunks. Formula 1 cars also have wing-like appen‐
dages on the front of the car. These are like the wings of an airplane but inverted so that
instead of pulling the vehicle up, they actually push the vehicle down. These wings,
therefore, increase the normal force, and their effects are proportional to speed so that
more downforce is available at higher speeds...just when you need it. In fact, some very
fast cars create so much downforce that if the road were inverted, the car would remain
glued to the pavement and be able to drive upside-down.
The trade-off for this increased cornering limit speed is increased drag caused by the
airfoils. This limits the top speed of the vehicle in areas of road that have no corners. It
is good practice to allow users to select an angle of attack for their vehicle's airfoils. This
forces them to choose between the option of higher top speed with slower cornering or
faster cornering with lower top speed.
You may notice that on some raceways, the corners are not flat. This is called roadway
bank or superelevation . In a corner where the car would normally skid, the supereleva‐
tion helps keep the car in the turn because as the car is inclined, a force component
develops that acts toward the center of curvature of the turn (see Figure 17-2 ).
Figure 17-2. Superelevation