Tire Pressure formula (simplified)

[swathdiver]

All that is doing is assuming load is a linear relationship with pressure, and then dividing evenly amongst the tires which doesn't take into account the rear tires need more pressure when loaded.

Proper way is to look up the TRA load vs inflation tables for your tire size, then use GAWR divide by two for each axle.

As mentioned in my particular post, the inflation tables were incomplete at 5 psi increments and not linear but graphing them out on Excel helped fill in the blanks.

i dont do math, i read the sidewall of the tires and add air.

Scotty, you're a smart guy but need to some tire learnin' my friend! Listen to the fellas here.

 

[Scottydoggs]

Scotty, you're a smart guy but need to some tire learnin' my friend! Listen to the fellas here.

no i literally dont do math, its the devil!!! lmao.

tires have a load rating right on the tire. the door sticker tells you what you can carry per axle. with max psi hot and cold. dont need to be a rocket scientist here. buy tires that meet or exceed your needs.

 

[swathdiver]

But some math and thinking is involved when switching to a tire that isn't on the door sticker, such as when going from a P-Metric to an LT or a different size.

My old Buick came with 215-65-15 tires @ 32 psi all around. But on the rear I ran 235-60-15, same circumference in inches with a BFG Radial T/A (82") but if we ran them at 32 psi the centers would wear out. So after some trial and error and many passes at the track, we settled on 26 or 28 psi (escapes me now) for best traction on the street and track. This car would do 1.7X short times on these radials with no burnout. The fronts were bumped to 36 psi for less rolling resistance and no wear issues. The car was thus set up to drive across country and go racing without fooling under the hood or with tires, been there and did that, and it was a pain.