Vehicle is hard to steer and wheel gizmos turn red

Question

I have a bus vehicle with rigidbody mass 8k and all vpp wheel colliders. I set adjust position to wheel mesh. When I play and steer the bus, it's hard to turn left or right. Wheel gizmos have red color. So what probably reason in my problem?

Thanks

Answer 1

Red gizmos mean that the springs are too weak to support the vehicle's mass. Configure the springs in the VPWheelCollider components using this rule of thumb:

    Spring Rate = vehicle mass / number of wheels * 2 * 9.81 / suspension distance

For 8k mass and 4 wheels with default suspension distance (0.25) the spring rate value for each wheel would be 156960:

    Spring Rate = 8000 / 4 * 2 * 9.81 / 0.25 = 156960 (Newtons per meter)

Additionally, you may want to configure dampers to roughly Spring Rate/20 to reduce the oscillations (Damper Rate = 7500).

Source:
https://vehiclephysics.com/user-guide/vehicle-setup/#springs-and-dampers

Being hard to turn left or right has several approaches:

• First, ensure to configure Steering Aids > Steering Limit to Sport in the Vehicle Controller. This way the vehicle will steer as much as permitted by the tires.
• Configure Center Of Mass and Inertia as described here.
• Adjust the Inertia Bias to match the expected behavior:
  • If it's hard to turn, move the slider towards negative values.
  • If if turns too much, move the slider towards positive values.

More information on configuring the inertia:

https://vehiclephysics.com/blocks/inertia/