The tyVehicleWheel helper defines a normal (non-physical) wheel - a wheel whose position each simulation step is computed analytically (via a ground raycast/sweep and a suspension force calculation), rather than being driven by a fully-simulated PhysX rigid body and joint chain.
tyVehicleWheel and tyVehiclePhysicalWheel both represent a wheel, but work very differently:
Normal wheels (this helper) are cheap to simulate and behave very predictably, but their suspension isn’t a real simulated spring - each step, ground contact is found fresh and the wheel is placed directly at that result, which can occasionally produce sudden, snapping motion (for example, losing contact with the ground entirely). Collisions with other active rigidbodies can also produce unstable behavior.
Physical wheels are genuine PhysX rigid bodies connected to the chassis through a real joint chain (including a suspension spring joint), giving fully-simulated, physically continuous suspension motion, and with real mass/inertia that can be affected by other forces and rigidbodies in the scene.
Either type can be converted to the other at any time using their “Convert” button.
tyVehicleWheel helpers are created from a tyVehicleChassis helper’s “Create chassis part…” menu, or a tyVehicle helper’s “Create vehicle part…” menu - not from the Create panel.
Pressing the “transform” button will temporarily sever the parent/child relationship between the helper and its children (ex: meshes parented to it), allowing you to move/rotate/scale the helper without affecting its children. This allows you to do things like reposition the helper without moving its children with it. Depressing the “transform” button will restore the prior parent/child relationship.
The “fit…” menu has options which allow you to match the position/orientation/scale of the helper to its child meshes.
The “flip” button will flip the transform of the helper along its dominant axis, without affecting its children.
Steerable: when enabled, this wheel will be used to help turn its vehicle.
Steering mult: a multiplier on the vehicle’s overall steering input, applied to this wheel specifically. Negative values steer this wheel in the opposite direction, useful for rear wheels on a vehicle with four-wheel steering.
Max angle: the maximum steering angle this wheel can turn to.
Footbrake: a multiplier on the vehicle’s overall brake torque, applied to this wheel specifically.
Handbrake: a multiplier on the vehicle’s handbrake torque, applied to this wheel specifically.
Parked: when enabled, this wheel will be locked in place, as if the vehicle’s parking brake were permanently engaged on it.
Mass: the mass of the wheel in the PhysX vehicle model used to simulate its motion.
Damping: the damping applied to the wheel in the PhysX vehicle model used to simulate its motion.
Friction: the overall tire friction/grip of the wheel.
Front stiffness: the wheel’s longitudinal (forward/backward) tire stiffness.
Side stiffness: the wheel’s lateral (sideways) tire stiffness.
Stiffness/damping: the stiffness and damping of the wheel’s analytical suspension spring.
Range: the total suspension travel distance, from fully extended to fully compressed.
Rest offset %: the wheel’s resting position offset within its suspension range, as a percentage, when no forces are acting on it.