Many people don’t know how to determine the correct air pressure for their automobile tires. It is because of this (and because many people don’t even bother to check) that more than 50 percent of cars are driving around on improperly inflated tires. While the average tire pressure is 32 pounds per square inch (psi), it is easy to find out exactly what the pressure for your tires should be.
Determine the proper air pressure
There are two numbers you’ll need to find, the manufacturer’s recommended tire pressure and the Maximum Cold Inflation Pressure for each tire. I keep a small notebook in the car to monitor fuel efficiency and watch for potential problems. I’ve written these numbers down inside that notebook so I don’t have to constantly hunt for them or try to remember them.
Check the placard
Vehicles 2003 and newer should have a placard inside the driver side doorframe. This placard will note the tire size and tire inflation specifications for the vehicle. Older vehicles might have the information in this location, in the glove box, or in some other location. You might have to do a little hunting to find it. The owner’s manual might also contain information regarding tire pressures.
The number you want here is the recommended air pressure for the tires (including the spare).
Check the sidewall of every tire (including the spare)
The sidewall of every tire provides a lot of information. For this activity you’ll want to find the Maximum Cold Inflation Pressure. Look for a number followed by “psi”. This number will tell you the maximum air pressure you should put into the tire while it is cold. As a tire heats up (either through driving or sunlight on the tire) the air inside expands, increasing the air pressure. Checking and inflating your tires when they are cold gives the best and most accurate results. Check out my article on “How to maintain the correct pressure in your automobile tires” for more information.
Recommended pressure or overpressure
While everyone agrees that the manufacturer’s recommended pressure should be the minimum pressure a tire is inflated to, there are some people that recommend a higher pressure. I’m going to provide some of the arguments for increasing the pressure in your tires but (to cover my rear) my recommendation is to just stick with keeping your tires at the manufacturer’s recommended pressure.
The recommended tire pressure is a compromise between fuel efficiency, handling, safety, and comfort. Increasing the pressure will impact these parameters. And never inflate a tire beyond the Maximum Cold Inflation Pressure marked on the tire sidewall.
- Increased fuel economy due to lower road resistance and tire flex
- Longer tire life and better wear due to less friction, sidewall flex, and perhaps improved impact resistance
- Improved handling, including less chance of hydroplaning and better cornering
- Rougher ride because the tires will absorb less energy
- Older tires or tires with flaws/damage may not tolerate higher pressures
- Liability / warranty / insurance issues
- An increase in tire temperature (hot sunny day, extreme braking, etc.) could push the pressure past the maximum pressure rating
- Your ride might be less quiet as more energy is transmitted into the suspension
You can try raising the pressure a little bit at a time (do the same amount for every tire) until you find the optimal pressure for your vehicle and driving style. Think of it as a small experiment. Play with it until you find what works for you. And do your own research.
Other factors to consider
Every 1,000 feet of elevation above sea level reduces atmospheric pressure by 0.5 psi. This means that the pressure in the tire is increased by 0.5 psi. At 6,000 feet of elevation, a tire gauge will read 3 psi too high. If you live at higher elevations you should take this into account.
Heavy loads or towing
Higher tire pressures may be recommended when hauling heavy loads or towing. You may have to do a little research to figure out what these pressures would be for your situation.
Seasons and outside temperature
While pressures should be taken when the tire is cold, cold itself is a relative term. For tire pressures, cold means somewhere around 70 degrees Fahrenheit. You’ll have to compensate for temperatures that are significantly above or below 70 degrees F. Tire pressure will change about 0.5 psi for every 10 degrees F difference (increase for heat, decrease for cold). This can significantly affect your efforts to keep your tires properly inflated.
Also, it is untrue that reducing tire pressure will increase traction on snow or ice. You’ll just end up damaging your tires and having to fill them back up again (if they survive).
The bottom line is that the optimal tire pressure for your vehicle is somewhere between the vehicle manufacturer’s recommended pressure and the maximum cold pressure rating of the individual tires. You can experiment a little and find what works best for you or you can simply use the recommended pressure and not worry about it. It may not be the most efficient pressure but at least you won’t be running around with under-inflated tires.
Be sure to check out my articles on “How to maintain the correct pressure in your automobile tires” and “Environmental, safety, and cost benefits of properly inflated automobile tires”