Cars can have two or four ball joints on the front wheels. If the car has McPherson struts, it only has two ball joints, located at the bottom of the wheel hub. If it has shocks and springs, it has both upper and lower ball joints.
Although all ball joints connect the vehicle’s wheel hubs to the rest of the suspension, they are not all load bearing. "Load bearing" or "non-load bearing" refers to whether the ball joint carries the vehicle’s weight.
Load-bearing ball joints are much more likely to wear out than non-load-bearing ones. When inspecting the ball joints, pay particular attention to the load-bearing ones, as they are at a higher risk of wearing out. For vehicles with McPherson struts, the strut acts as the load-bearing ball joint.
First Signs That a Ball Joint Might Be Bad
Since ball joints are hidden under the car, it is not easy to see where they are and what condition they are in. For this reason, they are often forgotten about until they start causing problems. However, there are a number of signs to look for which could indicate a problem with the ball joints. Keep in mind that none of these definitely mean that the ball joints are bad; other problems with the suspension and steering can cause the same symptoms.
For most people, the first indication that they have a problem with their ball joints is a faint, intermittent banging sound that seems to be coming from a corner of the vehicle. This sound is usually more pronounced when going over a bump or dip, or when going around a corner. This is not the same as the clicking sound made by worn CV joints (constant-velocity joints) when going around corners. This sound is more like somebody hitting a piece of the metal structure with a hammer.
As time goes on, this sound becomes louder and more frequent. It is especially pronounced when the weight of the vehicle is transferred off and onto the wheel, such as when driving through a pothole. Left long enough, the sound of a worn ball joint can become a loud, creaking bang, similar to the sound of the bottom of the car hitting the ground.
Worn ball joints can affect the vehicle’s steering. This can manifest in a number of different ways, usually making the steering sloppy or stiff. Which effect it has is largely dependent upon how the ball joint is wearing. If a vibration can be felt in the steering wheel when the vehicle is being driven down a straight, level highway, it could indicate a worn ball joint.
Another easy to recognize worn ball joints is uneven wear in the tires. If the outer or inner edges of the front tires are wearing faster than the rest of the tire tread, then there is a good chance that the ball joint is worn. If both edges are wearing faster than the middle, the problem is not the ball joint, but rather, under-inflation of the tire.
Cupping on the inner edge of the tread is also an indication of bad ball joints. This cupping is not usually visible, but should be discernible by touch if a hand is run over the tread of the tire.