This article describes a feature in the first Apocalypse Rising
Wheels are crucial vehicle parts that allow the car to move. Missing a single wheel makes the entire vehicle useless, so it's a good idea to shoot out the wheels of cars if someone is stealing one, or if you are chasing a vehicle. This will make the car immobile. Wheels spawn in almost every building in the game, especially in industrial spawns. It takes at least 2-6 tires to fix a vehicle, depending on what vehicle it is.
Don't carry wheels around unless you have seen a car and are trying to repair it as wheels take up important inventory spaces. This will render a lot of your space useless. If you see someone carrying wheels, scrap metal, or other car parts, assume there is a car nearby and try to find it.