How Your New & Used Tires Support a Car

If you’re a lot like me (which hopefully you’re not), then you wonder how small 17” Used Tires can support a whole car - and sometimes even a truck!

Let’s start off with some easy features of the car:
Vehicle Manufacturer Specifications
- Every manufacturer usually - and is supposed to - state the recommended air pressure for your new & used tires. The typical psi is 30psi for most passenger cars. At this pressure, the new & used tires can inflate while lifting the car off the ground and making sure that there’s maximum contact of the tire’s surface to the ground.

The Tire Sidewalls
- The sidewalls are made up of a mix that includes rubber and metal. The metal part of the sidewall is what allows the new & used tires to remain inflexible - making sure that the air in the used tires is actually capable of lifting the car while at the same time, the rubber allows it to flex with different hazards of the road.

When there’s not enough air pressure, the sidewalls would eventually begin to blowout and the metal that’s also inside the sidewall will begin to snap and break. Once the sidewalls are already suffering because of broken cords, there wouldn’t be sufficient air pressure to even raise the car to the best performance levels.

Tire Tread
- When you pay attention and inflate your new & used tires according to manufacturer specifications, it creates enough lift to get the used tires off of the ground. This is what allows the tread on the Goodyear Used Tires to make full contact with the ground. When there’s not enough pressure, the tread ends up curving inward - this means that the only the outer edges of the tread touch the ground. If there’s too much pressure, the tread can go convex - where only the center part touches the floor. Either way, you don’t want to be in either of these situations because they’re both pretty dangerous.

There’s some tire manufacturers that can sometimes publish a coefficient of rolling friction (CRF) for their new and used tires. People can use this number in order to calculate how much force it really takes to push just one tire down the road. The CRF honestly has nothing to do with how much traction a tire has or how much traction a tire is suppose d to have. It’s supposed to calculate the total amount of drag/rolling resistance that’s cause by new & used tires.

The CRF is pretty much just like any other coefficient of friction: The force that’s required to overwhelm and conquer the friction is equal to the CRF multiplied by the total weight of the tire.

There’s a lot that goes to calculating the psi, how much force tires need, and all that good stuff. You can either:

1. Go to places like Goodyear & Goodyear Used Tires so they can calculate it for you; or
2. You can do all that math stuff by yourself. I think it’s just like statistics - getting the formula and then just knowing where to plug in the numbers. If you plug in the number in the wrong place, you get something totally different than what you’re supposed to get!