f150 4x2 tire pressure questions.

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Texas Hill Country
I'm trying to squeeze out every mile per gallon out of my 98 nascar f150. I have a new set of firestone destination LE's on it. Love the tires. The door jamb says to set the front tires to 26psi, and the rears to 29psi. The tire itself says the maximum inflation is 44psi. I have been running the stock specs, I have a 400 pound load of sandbags in the bed all winter. Think I could go up a few pounds (like 5psi), in all the tires and not worry about anything? I wonder why ford suggested such a low tire pressure.
 
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3,118
Location
San Antonio, TX
99 f150XL 4x2 regular cab The label on my door jamb says 32f/35r psi. I don't understand why Ford recommends a lower front psi when the front of the truck is heavier. When the bed was loaded with furniture I increased the pressures because on the highway the steering was lazy. I have experimented with different pressures with the bed empty and I couldn't tell any difference. Last week I bought new tires and the shop put 35 in all 4 and that's how I left them. Joe
 
Ford designed the pressures assuming that the truxk was loaded to capacity. This explains the higher pessure in the rear tires. A F350 dually calls for 55 psi front and 80 psi rear. Obviously the front weighs much more than the rear, but Ford listed the pressure for maximum load. For maximum fuel mileage - use the maximum pressure listed on the side of the tire (do not exceed the maximum pressure for the wheel - shouldn't be a problem in your case). This will not give the best handling or tire life, only the best fuel economy.
 
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If you are "trying to squeeze out every mile per gallon", then get rid of the sandbags! Oh, you need those for traction? So maybe there are some other compromises that need to be made as well. I would not recommend using what's on the sidewall as an inflation pressure. It's way too high compared to what Ford recommendeds, which means the shock and spring combination won't be suitable for the higher spring rate of the tire. You'll wind up bouncing all over the road - certainly a safety issue. 5 psi above the placard is a good number. Hope this helps.
 

JustinH

Thread starter
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6,132
Location
Texas Hill Country
Hey Joe, What size are the tires on your truck, i'm scratching my head trying to figure why my nascar f150 has a lower air pressure than your XL truck. My nascar is basically a dressed up XL truck with wheels, lowered suspension, and 255/70/16 tires, and a few appearance details. I might go up a bit more on the air pressure to your specs and see what the deal is. Capri, yeah I have to have the sand back there on a plastic pallet to keep the rear from sliding all over the place. It has a 373 open rear end, with new tires and weight over the axle, the truck does great in the snow. Not as good as someones awd european wagon, but it does good enough for getting to work and back. Justin
 
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