Cupped Tire Wear
![A cupped tire.](graphics/cupped-tire-wear.jpg)
Worn or damaged suspension components like bad struts and shocks result in cupped tires. They are responsible for preventing the tire from bouncing up and down after hitting a bump in the road. The damping effect of the shock prevents the suspension coil from oscillating.
![Hub and Bearing](graphics/wheel-bearing-and-hub.jpg)
Cupped tires and bad wheel bearings make a similar growling noise while driving. This problem can make it difficult to distinguish between the two in operation.
![Cupped tires vs wheel bearing diagnosis.](graphics/suspension-cupped-tires.jpg)
A cupped tire changes its pitch from one surface to another. This change in pitch is true with all tires but much more pronounced with a cupped or scalloped tire.
![A shock bounce test.](graphics/shock-bounce-test.png)
Perform a jounce test to verify a bad shock. Be careful not to damage the bumper. After pushing down, the bumper should return to normal and not continue to bounce.
![Wheel Bearing Noise](graphics/wheel-bearings.jpg)
A worn wheel bearing causes a growling sound in operation. The outside wheel of a turn with the vehicle's inertia and weight leaning on it will be loudest. A bad right front bearing will be loudest while turning left. Raise the vehicle and grab the tire at the top and bottom. Rock it back and forth feeling for looseness; there should be little play, if any.