Why do/did people kick the tires of a car?

[Johnny_L.A]

Previous thread 1

@ralphredan

If you’re old enough, it does make sense.
During the war, rubber was rationed and most tires you could get were worthless retreads.
Good tires were a key part of a used car deal, and at times you would buy a wreck to get the tires.
There were few protections against worthless tires.
If you kick a few tires, it’s easy to spot the retreads. No-one actually does it any more, but at one time it was the smart thing to do.

@Una_Persson

One explanation that I have heard was that it was to rock the wheels to check for a bad tie rod or bearings.

I can testify that you can hear/feel a really bad wheel bearing or rod bearing by kicking the tires hard enough, but it’s absolutely not a reliable or repeatable thing to do. And if it gets bad enough to hear by kicking the tires, then the suspension is probably “24-carat fucked” on that wheel.

I can also testify that once I discovered a brake caliper that had not been installed properly after a brake job. I was kicking the tires of a friend’s car as a joke, and noticed a strange rattle. Turned out he hadn’t installed the anti-chatter spacers properly (not any real danger on this car, since they typically rusted and fell off, but it sure amazed her that I could detect it it with my innate car wisdom…).

Previous thread 2

@ricepad

According to my dear old dad, who used to work in a garage, and who is still pretty handy with a wrench, tire-kicking was the time-honored way to check out the condition of a car’s suspension, specifically the king pins and king pin bushings. In the good ol’ days, king pin bushings would wear at a fairly reliable and predictable rate. Eventually, the king pins would rattle around in the bushings, indicating that the car had a significant number of miles on it, and that it was time to have the front suspension redone. In order to have a kick reveal the rattle, though, the front end has to be jacked up. A good kick will tell you, roughly, if the miles on the odometer are reasonably representative of the miles indicated by the king pin bushing wear.

You can get the same idea by grabbing the top of the tire and giving it a good shake, but then you get your hands dirty.