// Change the material depending on the speed of rotation
var fastWheelMaterial : Material;
var slowWheelMaterial : Material;
function Update () {
if (rigidbody.angularVelocity.magnitude < 5) {
renderer.sharedMaterial = slowWheelMaterial;
}
else {
renderer.sharedMaterial = fastWheelMaterial;
}
}

using UnityEngine;
using System.Collections;

public class example : MonoBehaviour {
public Material fastWheelMaterial;
public Material slowWheelMaterial;
void Update() {
if (rigidbody.angularVelocity.magnitude < 5)
renderer.sharedMaterial = slowWheelMaterial;
else
renderer.sharedMaterial = fastWheelMaterial;
}
}

import UnityEngine
import System.Collections

class example(MonoBehaviour):

public fastWheelMaterial as Material

public slowWheelMaterial as Material

def Update():
if rigidbody.angularVelocity.magnitude < 5:
renderer.sharedMaterial = slowWheelMaterial
else:
renderer.sharedMaterial = fastWheelMaterial