I bought a used 97 f150 extended cab that came with
265 /75 r16 instead of the stock 255/70 r16.

The tires can hold up to 50 psi. What amout of psi should I inflate the tires to for maximum fuel efficency.? I mainly use the truck to haul a 4700 lbs. boat.

Is there a scientific formula to calculate this?


Thanks

 

No science, but this is what I do......

I've got the same size tires and load rating. For MAXIMUM gas mileage, go with the 50 psi. But, it'll ride pretty "stiff".

For everyday, empty driving, I keep the rears at 40 and the fronts at 44. When I haul or tow, I'll pump up the rears to 50 and leave the fronts at 44.

I just came up with these numbers by trial and error. I tried lower pressures, but it made the truck feel too "mushy". Higher, and it was too "stiff". So far I have over 20k on these tires, and they still look like new.

 

I run mine around 35 psi in all 4 tires

 

50 psi is the absolute maximum the tires will safely hold. i would not suggest driving with that much pressure. you do want higher psi when towing/hauling though. i would go about 32-35 empty, 40 loaded.

 

Not trying to be a "know it all", but the 50 psi is the MAX pressure when the tire is cold. Once you start driving on it, the tire will heat up and the pressure will go up quite a bit.

The reason you need to have the MAX cold psi when loaded is so that it'll actually keep the tire temp lower.

I have a small utility trailer with little 12" tires on it. It's Max cold pressure is 60 psi. One time I didn't check and it was down to around 35-40 psi. I loaded it up with bark mulch and only drove it about 5 miles. When I got home you could barley keep your hand on the tire, it was so hot. An hour or so later, after the tire had cooled down and I brought it back up to 60 psi (cold), went back for another load and when I got back home, the tire was just warm to the touch.

Just my experience in the whole deal. Everyone's comfort level will be different on what the pressure should be when empty, but if you're getting to the maximum load on the tire, you should have it set to the maximum cold psi.

Happy (and safe) Trucking!

 

your actually supposed to base your psi on whats stated inside the door of your truck on the specifications placard. It will tell you how much front and how much rear pressure your supposed to use. Your owners manual might also list optional tires sizes and pressures. If not, a reputable tire dealer near you will have a chart of optional tires for your truck. This is so your truck behaves the way Ford wants it to!

 

That's only if you stick with the size and load range tire that is also listed on the door jamb.

My door jamp sticker says P255/70/16. And you are supposed to have the fronts at 29 psi............ I think the MAX cold psi for for that tire was like 40. It's a passenger car load rating!! 29 PSI is just too low IMO.

Since I now have LT rated tires (that are actually what a truck should have from the factory), I go by what the tire says is the max psi (50 for load range C). I also go by what works for ME. If you feel 29 psi is fine for your setup, that's what you should run. The original post was for aftermarket LT tires and wanted other's opinions.

In this case, the door jamb sticker does not apply anymore, because of the aftermarket tires.

Not flaming you, just making sure that everyone realizes that we're not talking about the stock tires anymore.