[scottydl]

How do you guys calculate the correct psi to run in your tires? Obviously our cars don't have a handy sticker in the driver's doorjamb to give that guidance.

I just got new tires on my '69 Executive, and according to the sidewall it mentions 35psi for max load 2028 lbs. However I weighed the car and the front axle is 2640# (so average 1320# each tire) and rear axle is 2140# (average 1070# each wheel). The rear is barely half of the tire rating, but obviously cutting the psi in half would be way too low.

The shop had aired the tires up to 37-38 which felt pretty harsh, and deflating them to 32-33 made a significant difference and feels pretty smooth. But if I can/should lower the psi even more based on the car's actual weight, I've got no problem with that.

[b-man]

Run as much pressure as is practical for even tread wear and a nice ride.

I’d try 32 psi and adjust up or down depending on how you like the ride and handling.

Fuel efficiency means running more air pressure, but not so much that the ride quality suffers.

Let’s face it, most of us won’t get enough miles on our tires before they’re old enough to need replacing so stressing over getting perfectly even tread wear isn’t worth it.

Keep in mind that in a corner the car’s weight shifts to the outside putting added stress on those two tires so you need to have tires that can handle more than the static weight on that particular axle.

[scottydl]

Thanks b-man. I've owned full size cars most of my adult life, and the newer ones usually hovered in the low 30's for psi recommendations. My 2019 Cadillac CT6 says 32 front and 35 rear, which is interesting as I figured the heavier front of the car would need more tire pressure and not less. That car is big by today's standards, but overall is probably a couple hundred pounds lighter than my Executive -- and has 20" wheels/tires with a much smaller sidewall. Apples to oranges perhaps.

On a related note, this whitewall tire purchase was coupled with a new set of chrome wire wheels -- something I've been wanting for years (decades?) and discussed last year in this Tire/Wheel Decisions thread while looking for something used. I never found anything that I liked locally, in the right condition and with the correct width + bolt pattern. So believe it or not, after researching extensively I ordered a set direct from a supplier in China that I found online and purchased through AliBaba.com. Took a few weeks to arrive as expected, but the communication was good along the way and the price was reasonable enough to take the chance. They mounted up great and are true spinner knock-offs, so that was a learning experience too. I'll post some pics when we have another nice day.

[gto4ben]

1969 Owner's Manual says 24 psi front, 28 psi full load. 24 psi all around for reduced load.

[b-man]

Originally Posted by gto4ben

1969 Owner's Manual says 24 psi front, 28 psi full load. 24 psi all around for reduced load.

And those pressures would work for original size bias plies, modern radials in a similar size would definitely want higher pressure.

[scottydl]

Originally Posted by b-man

And those pressures would work for original size bias plies, modern radials in a similar size would definitely want higher pressure.

That's what I was thinking. I still have my full size spare on a bias ply tire in the trunk... for nostalgia purposes I guess! It could be the original, and I'm not sure how far I'd get on a 55 year old tire!

[indymanjoe]

I would start off at what pressure ratings are on the tire.