The ball joints that wear out first are the lower ball joints.
Lower ball joints are often the first ball joints to wear out when compared to the upper ball joints.
Lower ball joints bear the brunt of the vehicle's weight and also absorb more shocks from road conditions.
Also in some designs of suspensions like the SLA or Short Long Arm, the lower ball joint is a load bearing part, which directly supports the weight of the vehicle.
And in strut systems like MacPherson Strut systems the lower ball joint is also a follower, although it still experiences significant stress during braking and also cornering.
The lower ball joints are also exposed to more direct impact from things such as potholes and other hazards in the road and rough road conditions which also increase the wear on the lower ball joints.
And the constant movement of the ball joint during driving as well as turning also creates friction, which can also cause wear over time.
Also the absence or presence of lubrication in the ball joints also affects the ball joints lifespan.
Some ball joints are sealed and don't require any extra greasing but others may need grease and if so they should be greased often.
It's recommended that you replace both upper and lower ball joints at the same time if you can do so as it will help prevent any future problems down the road.
Ball joints on average last between 70,000 miles to as long as 150,000 miles.
Although the lifespan of the ball joints can also vary significantly depending on the road conditions and your driving habits.
The signs that your ball joints are bad and need replacing include rattling or clunking noises, especially when you go over bumps or turn, a loose or wandering steering wheel, uneven tire wear and vibrations in your steering wheel throughout your vehicle.
If you notice any of these symptoms of the ball joints failing you should have the ball joints inspected or if you can do yourself you should inspect and replace them as soon as possible.
Worn ball joints often create a clunking sound or a knocking sound, most particularly when the suspension moves over bumps or when you turn the steering wheel.