# Vehicle Dynamics

Add-on components modifying the vehicle's handling and behavior.

You could write your own add-on components easily if the provided components don't fit your needs or you need other features.

### VPAntirollBar

Anti-roll bars (also "stabilizer bars" or "sway bars") connect the two wheels of the same axle allowing a limited degree of freedom between their suspensions. When one of the wheels is pushed upwards, the stabilizer bar transfers a portion of that compression force to the other wheel, so its suspension compress as well. This reduces the body lean in turns at that axle.

Axle
The axle this anti-roll bar component will be attached to.
Mode

Several working modes are provided:

• Stiffness: configures the stiffness ratio of the bar.
• Spring rate: configures the spring rate of the bar. The spring is applied based on the difference of travel between both suspensions.
• Legacy: applies an anti-roll rate based on the difference of compression ratio between both suspensions.
Stiffness
0 removes the anti-roll effect (fully elastic bar). 1 means a rigid, totally inelastic bar.
Spring Rate
Spring rate transferred from the less compressed to the most compressed suspension. For example, if the difference in the suspension travel is 10 cm, then the transferred rate will be 0.1 x Spring Rate.
Rigidity
When one suspension is compressed the other is lifted as much as specified in this parameter. 0 means the less compressed wheel is untouched. 1 means the less compressed wheel is lifted as much as the most compressed wheel, so both "bounce" at the same position. This typically causes instabilities. Recommended value is 0.5.
Anti-roll rate
Legacy mode only: amount of spring rate transferred between suspensions based on the difference in their compression ratios.

### VPAeroSurface

Stand-alone component (it doesn't require a VehicleBase-derived component) providing drag and downforce based on the velocity of the vehicle. The forces are applied to the vehicle at the position of the GameObject containing this component.

The recommended setup is having a VPAeroSurface GameObject at the middle of each axle, at least at front and rear. These components can configure the behavior of the vehicle at high speeds.

Drag Coefficient
Coefficient for the drag force with the speed. The force is applied counteracting the vehicle's velocity.
Downforce Coefficient
Coefficient for the downforce with the speed. The force is applied at the transform's position in the transform.down direction.

The force magnitudes are calculated with a simple quadratic formula:

$$F = \rho \times v^2$$

where $F$ is the force in Newtons, $\rho$ is the coefficient and $v$ is the vehicle's speed in m/s.

Important:

Aerodynamic forces require keeping an eye on the suspension (you can use the Telemetry). The extra downforce will compress the suspension as well. The suspension must not reach the 100% compression (1.0) or unwanted effects will occur. Stiffer springs or progressive suspensions might be required for avoiding that.