What should I run for tire pressure (psi) for a 2004 STX with FX4 wheels and Goodyear ATX's ?
This is for everyday driving... and the tire says 50psi max... but I am not loaded to the max.

What do you recommend?

 

You tire pressure is on the driver's side door sticker.

Remember that air pressure is relative to temperature. So depending on the time of the year, you may need to add air.

Fronts should be 30 PSI.
Rears should be 35 PSI.

Always Always Always set your tire pressure to what the door sticker says, NOT to what is written on the tire.

I check my tire pressure about once a month, in the morning before I goto work, when the tires are cold.

 

The door sticker is for the stock tires. These are FX4 4x4 wheels/tires and are rated totally different. The stock tires are rated to 35-ish, and these are rated to 50psi.
I guess I am looking for a recommended psi from an FX4 owner with THEIR door sticker...

Update:
I just read the tire sidewall, and they are LT tires with 110 & 113 load rating C.

According to Goodyear website:
Tire Size / Load Range / Speed Rating / Sidewall Approved/ Rim Width Meas. / Rim Width Section / Width O.D. / Max. Load
LT275/65R18 / C / OWL / 7.5- 9.0 / 8 / 10.9 / 32 / 2,535 @ 50

P265/70R17 / SL S / BSL / 7.0- 9.0 / 8 / 10.7 / 31.6 / 2,535 @ 35

 

Not to knit pick you, or "prove you wrong".
Just pointing out a fact on the Goodyear website:

Goodyear Tire Inflation

"How much air should I put in my tires?"

Proper inflation is the single most important part of tire care. The inflation pressure on the side of the tire is the MAXIMUM operating pressure. It is not necessarily the right inflation for your vehicle. Always use the inflation recommended by the vehicle manufacturer. You can find it in your owner's manual, posted on the edge of the driver's door, on a door post or on the inside of the glovebox door.

 

I think the disconnect is that I swapped wheels/tires, and not that I am not following the Ford recommended infaltion.

THerefore the door sticker was for the old tires. THe new tires are from an F150 FX4 4x4 with "LT" rating (Light Truck) tires, not the "P" rating (Passenger) tires that came on my STX.

I went to pick up my plates at the dealership last night. After looking at about 20 vehicles that were FX4's, finally found once with with Goodyear "LT" tires (not BFG "P" tires), we found the door sticker to read 40psi. All other "P" door stickers read 35psi.

So there we have it, 40psi recommended by Ford for that vehicle, with those tires.

 

The table you quoted from the Goodyear website shows max load and max pressure both relative to eachother.

If you have lower pressure, you can only support a lesser load.

Goodyear's website also has load/pressure tables to show which is relative.

The only tables I found didn't show the 275/65/18 tire.

My recommendation to you is to set the pressure to 30/35 which is probably what your door panel says. Which is what both Ford and Goodyear recommend.

Also since you stated it would be for city driving anyways. Since you're not loading the bed and worried about load vs pressure.

Maybe if you were hauling a bed full of concrete bricks every day I would say increase the pressure to match the load.

Your door panel should show GAWR value, for instance my Supercrew says 3800 in the rear.
So that's 1900 per tire, well below Max Load of 2500.

 

I agree 40PSI sounds good.
I just didn't want to see you set those tires too high.

Glad to see you found a door sticker that matches.

 

caveman978,

You can only go by the door sticker IF you still have those exact same tire specs that's on the sticker. Those are usually a P (passenger) rated tire that has a max PSI of anywhere between 35-40 psi.......

My door sticker says 30 front and 35 rear with a P255/70/16 tire...... I had those and ran that pressure and it just plain sucked... The truck was so mushy feeling and felt like all the tires were flat. Pumped them all up to 40 (which was the max psi listed on the tire) and the ride was much better....

Got tired of those puny tires really fast, and was going to get a travel trailer soon, so I wanted LT tires. Got me some LT265/75/16. Wow, what a difference! When I'm not towing I keep the fronts at 44 and the rears at 40. When I tow or haul, they all get 50.

I've got over 50,000 miles on these tires and they still have at least another 10,000 in them, but that would put them to the wear markers and I don't want to go that low....

Gonna get some new skins later this month..... Same size and rating, but these will be the Open Country AT's from Toyo.

 

The volume of air in your tire is what holds the vehicle up properly. The pressure is a factor of the volume. Passenger or LT has nothing to do with it. The factory inflation is the basis for everything. If you were to replace the factory tire size with something that had twice as much volume available, you would fill it with the same amount of air, and the pressure would be half of the original. (This is extreme, but it makes the numbers easy). You do have to ensure that the tire is capable of supporting your vehicle, but for passenger vehicles, this is hardly an issue. If you take a 31x10.50x15 @ 30 lbs and replace it with 33x12.50x15 you would probably want to drop the pressure to 28 lbs or so. Proper tire pressure is important to tire life and safety, if any one thinks they understand what the proper inflation should be better than the engineers that designed the vehicle, the only one being fooled is yourself. When changing from stock tire size, adjust pressures accordingly, watch for wear patterns. Since no one will probably ever measure the volume of air in their tires. Center wearing is too much pressure, outside wearing is too little.

 

The door sticker for the LT275/65R18 states 40lbs. If you are putting 50 in there at any time they are way overinflated.
At 50 the tire is rated at 2535lbs, times 4 for a vehicle of a gvwr of 10,000+lbs. Or have 5000lbs on just your rear axle. Way over payload.

 

Thanks for all your responses guys.
Trust me, I really DO know how to watch tire pressures. I even take tire TEMPERATURES... (even when not all four of them are touching the ground)...