Tire Pressures

[George G. Leverette]

One of the most important aspects to safety and performance is selecting the right and maintining the correct tire pressure. The problem is selecting the correct pressure. Some tire shops use the manufactures maximum recommended tire pressures. Other shops use 5 lbs less than the maximum pressure recommended by the tire manufacturer. Others use a standard 35 PSI on passenger cars. I have a set of Toyo Proxies on a PT cruiser 225X18X40 which is the correct pressure 35PSI standard, 45PSI 5 lb less than the 50 PSI manu max or can the maximun 50 PSI be used? I also have a new set of tires on a project car, Cosco fill all of their new tires with Nitrogen. Will Nitrogen read the same as air on a tire pressure guage? Will a tire expand and contract with Nitrogen like a conventional air filled tire?i

[BJSracing]

Nitrogen will read just fine on a tire gauge. It is only reading pressure. And no nitrogen will not expand and contract like oxygen will. There will always be a little variance but not where near the magnitude. I run 36 -38 psi in all my street tires unless it is a low profile tire then you tend to have to run more. Street slicks will run less. Depends on the make of the tire and the side wall and tread combo.

[MrChemist]

Will Nitrogen read the same as air on a tire pressure gauge?

Yes, Nitrogen will read the same on a tire pressure gauge.

Will a tire expand and contract with Nitrogen like a conventional air filled tire?

For our concerns as car guys, yes…on a molecular level, no (if you want the full explanation from a scientist, just ask; otherwise I will leave it out to prevent putting our readers to sleep).

Race car drivers will use nitrogen in there tires because the tire will not heat up as fast and run cooler. From the average Joe aspect, it is nice because it seeps out of the tires at a lower rate than “air”, meaning fewer fill ups. They say that Nitrogen will prolong tire life as well…this is a bit of a spin on truth. Air is comprised of approximately 78% nitrogen, 20.9% oxygen, 0.9% Argon, and 0.03% Carbon Dioxide (and various other sub components). They say that by removing the oxygen from the tire, you prevent oxidation from the inside out. This is scientifically sound thought, BUT; considering the life of the outer tread of the tire (and the driving habits of most of us) it is really a moot point. The outside of the tire will wear out LONG before we could really care about interior oxidation of the t