WheelCollider.motorTorque

Motor torque on the wheel axle. Positive or negative depending on direction.

To simulate brakes, do not use negative motor torque - use brakeTorque instead.

JavaScript

// spin the wheel forward

collider.motorTorque = 10;

using UnityEngine;
using System.Collections;

public class example : MonoBehaviour {
    void Example() {
        collider.motorTorque = 10;
    }
}

import UnityEngine
import System.Collections

class example(MonoBehaviour):

    def Example():
        collider.motorTorque = 10