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
No, you don’t need to do that, Jay.
Tire inflation is not brain surgery. 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.
You probably remember the Ford Explorer/Firestone debacle from the turn of the century. Firestone made tires for the Explorer that, when underinflated and subject to lots of heat, like on Texas highways, basically fell apart and led to high speed rollovers.
While the quality of those tires themselves certainly played a role in the epidemic, all tires can be vulnerable when they’re underinflated. 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.
Out of that whole Ford/Firestone disaster came a new safety feature called “Tire Pressure Monitoring Systems” or TPMS. Now every tire has its own built-in gauge and a way to communicate with the car’s computer. And if the pressure in any tire drops about 10% below its recommended level, an idiot light on your dashboard comes on.
So, on the bottom end, 10% is your lower limit. 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% or even more without too much concern. For instance, 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, and you may have welts on your head from hitting the roof when you go over bumps, but you won’t be creating a blowout danger. You may even experience sharper cornering and increased fuel economy, too. But the emergency room copayments for the welts will probably wipe out any gas savings.
So, the bottom line is that 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.