Tire presssure comparison

Unless it's a really unusual car (you never said what it was) 32 psi works well for just about any vehicle.

'71 Grande with Cleveland 4V 9" 3.73 posi. Also has some suspension mods like sway bars and rear air shocks you need to pump up now and then. At 32, she breaks traction too much. That is where all tire people set the pressure as that is what the tire manufacturer recommends for best wear. I was told to use the door sticker ratings as that is how the car's geometry is setup for best performance. While researching an article suggested by Steve, about clocks, I discovered the E70 is pretty close to my P235/60. Have heard when converting tire pressure to P metric, you add 3 pounds. So 28 PSI front rear.

Take a piece of chalk, draw a line across the tread of the tire. Drive a few revolutions of the tire, inspect the line drawn. If it is disappearing in the middle faster then the ouside, lower the air pressure. If wearing faster on the outside edges, raise the air pressure. There should be even wear left to right. Did this with the monsters I have on the back of my 72, excellent results.

Recently read that exact info. While doing some research, I stumbled into the tire section. The recommendation was to draw a chalk line, as you said.

My question is, why does Firestone recommend 32 PSI while Ford recommends 28 PSI for the same tire.