The automobile manufacturer’s info sticker on the door panel usually lists the recommended tire size and pressure.
Let’s say the sticker says the recommended pressure is 32 psi.
But when you look at the tire itself, it says 44 psi max pressure. This is assuming the tire SIZE is the matching recommended size of the sticker.
Ok, confusion!
[li]Why does the tire itself, not say the recommended MINIMUM psi, and only the maximum?[/li][li]The car sticker is obviously the recommended MINIMUM psi, by the auto manufacturer’s standards not the tire manufacturer. Car mfr’s don’t make tires, tire co.'s do.[/li][li]Are you supposed to follow the tire itself’s info, or the car mfr’s info? 32 psi(car mfr) vs. 44 psi(tire)[/li]
I have found my own way of dealing with this.
My car sticker, does indeed say 32 psi. My tires say 44 psi MAX.
I subtract 32 from 44 = 12.
Divide 12 by two = 6.
32 plus 6 = 38 psi.
Using this method, I figure I really can’t go wrong. This way, there is little likelihood that I can be using too little, or too much psi. and it leaves room for the psi to fluctuate with natural temperature changes without undue stress on the tire.
The maximum tire pressure listed on the tires means simply that it is unsafe to operate a car with the tires at a higher pressure than that. It does not mean that this is the best pressure for the tires, just the upper limit.
Car manufacturers test their cars with a specific set of tires. Assuming that the tires on the car are the same size as the original equipment, this is the number you should use, but any number up to the maximum psi on the tires should be safe.
Remember that the recommended pressure on the car’s sticker is the cold inflation pressure. Make sure you are testing the pressure before driving the car anywhere. As you drive, the friction heats up the tires, which causes the air pressure to increase. If you air up your tires after driving for a while, overinflate by a few pounds, then check the pressure after the car has been sitting for a few hours and the tires have had the chance to cool. Then you can release any excess pressure.
Also, be sure to check the tire pressure regularly, especially when there has been a big change in temperature. Tire pressure goes down in cold weather, and up in hot weather. If you live in someplace like Chicago, this can make a signifigant difference.
Bottom line: if you want to play it safe, follow the car manufacturers recommendations for routine maintenance.
I am well aware of all of the above. I check my tires regularly with a tire gauge at least once every two weeks. I even check my “donut” spare regularly. I test psi before driving, before / during / immediately after inflation. It’s virtually impossible for me to OVER/UNDER inflate, as I am very meticulous about the whole ordeal.
The “MAX PSI” stamped on the tire itself represents the pressure above which the tire is likely to fail - less a sizeable safety margin, I’d imagine. It’s basically the tire maker saying, “Whatever you do, don’t exceed this pressure. We don’t guarantee this tire’s integrity if you do.”
The “ideal” pressure to which a tire should be inflated is largely a handling/ride issue. The tire is part of the vehicles suspension system, and it has its own effective spring constant and damping coefficient, just like the strut/shock assembly. These values will vary with the inflation pressure, so the car maker specifies an inflation pressure that (it feels) works best with the rest of the suspension components.
Apparently, the specifics of the tire are relatively unimportant (in this sense). By this I mean that changing from Firestones to Goodyears is likely to make less of a difference (in suspension dynamics) than changing the inflation pressure of either by 5 psi. Hence the “tire independent” pressure recommendation from the car maker. Start changing tire size, though, and all bets may be off.
This value does vary a lot from vehicle to vehicle, which is why the tire maker doesn’t even try to recommend an actual pressure. Realistically, the ideal pressure is more a function of the vehicle than of the tire.
Most things I’ve read advise following the recommendation of the door sticker.