An odd sequence of events

Question: I have a 1988 Chevy C2500 truck. I took it for an alignment. When I came to pick it up, I was told everything was fine. Not long after leaving the garage, the truck dropped down as if going to its knees. The body sunk down onto the chassis and almost punctured the tires. When I took it back, the mechanic said that the ball joint had failed but that it wasn’t his fault. They said the ball joint was worn out and its time had come. This seems very suspicious to me. Can I prove it was his fault?

A.G.

Answer: It is far more than suspicious, sounding more like a case of bizarre sabotage. No mechanic could align a car with such a worn-out ball joint, which is a crucial part of the suspension. A ball joint might be compared to a hip joint, bearing the entire weight of the upper body of the car. It is the main pivot point for the suspension and also allows the front wheels to turn.

On your Chevy truck, there are two ball joints on each front wheel, an upper and a lower. It is a traditional heavy-duty design that was once widely used on cars but is pretty much now limited to trucks.

Automakers know how crucial a ball joint is to the lives of the occupants, so they design them to almost never fall apart. A ball joint doesn’t fail from being worn; it must be totally shot to fall apart.

The fact that yours fell apart immediately after a mechanic worked on the front end suggests either gross incompetence in failing to recognize the problem or some kind of foul play. In aligning a vehicle, a mechanic does not remove a ball joint, so it doesn’t seem logical that he worked on the ball joint. More likely, he could have made some errors in completing the work.

Having said that, GM recognized not long after making your vehicle that the ball joint was problematic. In 1991, GM issued a technical service bulletin that outlined a warranty extension on the original ball joint and made several changes to the alignment procedure on the truck, according to Alldata, a publisher of automotive repair information. So it is possible that the ball joint was not only worn, but shot.

Even so, any good mechanic would have recognized the problem because it’s almost impossible to align a car with a badly worn ball joint. I would suggest you contact a Chevy dealership and find out if your vehicle still falls under the extended warranty issued in 1991. Good luck.

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Question: I drive a 2000 Dodge Durango with about 45,000 miles on it. The original tires are worn out. Would it be safe to use my full-size spare and buy just three new tires?

J.M.

Answer: It’s a great idea, but you’ll probably never find three other tires to match your spare. It’s important to have matching tires because the performance of tires varies so greatly. Different tires by even the same manufacturer have different treads, traction, rolling resistance and other factors.

The bottom line is that your vehicle will be less stable, particularly in an emergency situation. Different traction on one side of a vehicle will increase the chance that you’ll lose control on a slippery wet road. I would be particularly concerned with driving on unmatched tires on a sport utility vehicle, with its greater propensity to roll over in an emergency.

The correct way to get some use out of a full-size spare is to rotate all five tires at every oil change. That way, you end up with five worn-out tires at once. But I’m not sure it’s worth the bother. After all, one standard tire is worth $100 at most, and that investment should easily last 10 years or more.

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Ralph Vartabedian can be reached at ralph.vartabedian@latimes.com.