I have a 2017 Mazda CX-5 with 19 inch rims. I stopped at the gas station to check my tire pressures and top them off. My vehicle calls for 35PSI front/back. Anyway, I set the air compressor at the gas station to 35 and topped them off.
Upon getting home, I checked them with my digital gauge and they’re showing 37PSI when cold. I lowered them to 35, but was wondering if 2psi extra would actually make a difference? The tires have 8k miles on them.
The size of the contact patch is directly related to inflation pressure - meaning that even 0.00001 psi difference will change its size.
But I think you want to know how much pressure would be a significant enough change to worry about - and as others have said, if you are within a couple of psi, it doesn’t matter much. If you are looking for a practical solution, keep in mind that UNDER inflation is much, much worse than overinflation. Try 2 to 5 psi ABOVE what the vehicle tire placard says - and do this on a warm day. That way you’ll always have enough pressure in the tires.
And - No! - That amount of over inflation will not cause wear issues by itself. There are other things that have a much greater affect - alignment being the one most likely to cause problems.
And unless your digital gage has been calibrated and a compensation curve created, you really don’t know which is correct. 2PSI is within the acceptable error tolerance of the average pressure gage. Fortunately, +/- 2PSI is meaningless in the average car.
First off, those gauges are cheap. Keep one in your glove box.
The 19 inch rims are really low profile tires. I’m surprised at the factory setting is that high on a low profile Tire but you have the manual so you know.
2 pounds of air higher on a low profile Tire would be noticeable in ride quality. Those kinds of tires have the tendency to make the car ride like a Buckboard anyway. Two extra pounds can also make a noticeable difference in mileage on long trips by making the tire harder and making it roll easier, but harder means less grip, especially in the rain or snow hello oh yeah. Or around town driving if you don’t mind a little extra tire wear I recommend two pounds less than but you have to check your air pressure more regularly as it gives you less cushion just for the natural leakage that happens over time. But the tire wheel grip better in the rain and the snow with slightly less tire pressure. You see that in auto racing all the time with teams adjusting the way the car handles by adjusting air pressure. In a race cars or drag racing cars and motorcycles, fractions of a pound make a difference.
In my old Chevy Prizm I can tell the difference in ride with a 2 pound difference.
That’s a good question for a physics exam. My guess is that contact area is proportional to the vehicle weight divided by the tire pressure. So you’d get a decrease in contact area by a factor of 35/37 comparing 37 psi to 35 psi. About a 5% decrease.