What is the acceptable pressure range for the over- and under-inflation of tires?
Click & Clack Ray Magliozzi
Dear Car Talk:
The owner’s manual for our 2015 Toyota Camry recommends a tire pressure of 35 psi for all the wheels. I check the pressure monthly, and there may be a loss of one to two psi on a couple of tires. I crank up the compressor and, after a few tries, I finally get exactly that one psi in there. In the process of adding air, I’ll sometimes go over by half a psi or one psi, which I then bleed off. Do I need to do that? What’s the acceptable range for over and under inflation of tires? — Jay
You don’t need to do that, Jay. With tire inflation, you can muck around and get close enough, and still live a full and happy life. Of the two ways to miss your mark, underinflating your tires is the bigger danger.
Underinflated tires put a larger rubber contact patch on the road, create more friction and therefore run hotter. And heat can cause the tire’s belts to separate and come apart. Every new car now has a Tire Pressure Monitoring System or TPMS, which is a built-in gauge and a way to communicate with the car’s computer. And if the pressure in any tire drops about 10 percent below its recommended level, an idiot light on the dashboard comes on.
If your Camry recommends 35 psi, 31.5 psi would be the absolute lowest you’d want to let it go before adding air. You have more flexibility on the upper end. As long as you stay below the maximum tire pressure listed on the tire’s sidewall (which is different from the recommended pressure), you can overinflate your tires by 10 percent or even more without too much concern. For example, if 35 psi is recommended, and the maximum safe pressure listed on your sidewall is 44 psi, you can safely put 38 or 40 psi in your tires.
You can even go to 44 psi. You’ll experience a harder ride, but you won’t create a blowout danger. You may even experience sharper cornering and increased fuel economy.
So, when filling your tires, the recommended tire pressure is the best compromise between handling, comfort, fuel economy and safety. But it’s certainly fine to go over the recommended inflation by a psi or two. And going over is always better than going under.
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