Over my years of law enforcement, crash investigation, and collision reconstruction I have come to become more and more particular about my tires. I have watched people purchase tires from these “Used Tire Stores” and when I buy my tires I can understand why; quality tires are expensive. The question of how old is that tire and how was it serviced before it ended up for sale is a huge concern. I have watched people put their compact spare tire (commonly called the donut spare) on their vehicle and ride on it for weeks even traveling down the interstate a speeds way above the recommended rating on the tire. I have had a tire dealer (that sold new tires) try to sell tires and rims that are not safe combinations because they go against the vehicle and tire design. Needless to say, much to their dislike, I wouldn’t cooperate with them because it didn’t make them money; however, they did not end up in civil litigation either.
I have seen people do things to be trendy like lifting or lowering a vehicle way beyond the vehicle manufacturer’s intent. People lift and lower their vehicles by changing the size of their tire or wheels (this brings in a whole new concern if they change the rims because they too are rated and designed for specific applications) without consideration of the vehicle’s relationship to its tire design. Sometimes the tires rub, causing wear and damage to the tires, which becomes a safety issue. Each time you go up or down in the height of the tire you are changing the revolution speed of the tire. This in turn changes such things as the accuracy of the speedometer. The change in speed being displayed compared to actual speed may only be 1 or 2 mph difference at 5 or 10 mph, but 15 to 20 mph off at 55 or 60 mph.
With the complicated safety systems communicating with each other within a modern vehicle’s computer system and making decisions in milliseconds (especially things like airbags, traction control, and anti-lock brakes), having erroneous data generated by the use of improper tires yields not only a concern for a speeding ticket but to a vehicle’s improper response to conditions of a crash. If there is a need to change tire sizes, find a trusted and reputable tire company to walk you through the change so that you have the least amount of repercussions from the switch.
In part 2 of this blog we will go over where to find the proper tire and loading information for your vehicle, and what these values mean, to ensure you are getting the maximum safe performance from your tires.