Hi all,

I have a 98 F-150 XL, 4X4, 4.6 Love it! Except for the gas mileage, but hey what can you do I have a question about tire pressure. I have BFGoorich rugged trail t/a's on it . Nowhere on the tire does it give a recommended psi, except for a max (80) I even checked the BF website. No luck. Any suggestions? They are a 265/75R16.


Thanks for any suggestions!

 

The tire pressures are listed on the drivers side door jamb and in your owners manual.

 

Why not follow Ford's recommendations found on the driver's door as a starting point? The reason you'll never find a recommended pressure on the tire itself is that a tire can be used on a variety of vehicles.

Is the tire a P265/75R16 or an LT265/75R-16?

 

Must be an LT if 80psi is max. allowable pressure.

 

Thanks for the replies. THese aren't the original tires that were on the truck. I think they are oversized. Would that matter?


Thanks again!

 

I have the same question. I have Bridgestone Dueler AT's p255/70/R16 and I'm not sure what pressure I should be running.

 

My 97 F-150 Offroad says 35psi for the rear and 32 for the front, I believe. I usually run both at 35 PSI for what its worth. Tire wear and ride seem fine.

 

With a max of 80 psi, this sounds like a load range E tire. A load range E on your vehicle should probably be about right at 50-55 psi. If it was load range D 40 would be about right, 36 for a load range C.

 

How can you find out what the load range of your tire is?

 

It will be marked on the sidewall along with the size. An example is LT265/70R17 LOAD RANGE E.

 

It really doesnt matter what load range your tire is, for the most part.... unless you load up the rear.

Size A in load range C, is the same size tire as Size A in load range E. Unless you are towing large amounts, there is no need to crank the tires up over 40 psi unless you like a rough ride and worn out centers on your tires.

I run 35 in front and 40 in the rear of my truck with 6 ply 17'' tires.

Start out with the reccomendations on the door, and then adjust it from there if you don't like it.

 

It's the other way around. The size is not what matters, but the load range. If you look at the door on a vehicle equipped with P or LT load range c tires, it will show a pressure of 35 or 36. If you look at one equipped with Load range D it will show a pressure of 40. In this case size doesn't matter. If you run a load range E tire at 40 you will just wear it out too quickly or cause it to overheat. The sidewalls and belts are much stiffer and need more support to be properly inflated.
If it didn't matter there would be no reason to have a different max inflation.

 

Those numbers are based on the vehicles handling propertys.... In all the thousands and thousands of vehicles I've serviced, I've yet to see a model, such as a F-150 have a vehicle placard as you describe. It can be seen by jumping to a F-250 and so on...

There is not a difference in stiffness between any of the tires, they all have the same amount of plies....usually 2 nylon side wall, 2 nylon tread, 2-3 steel tread. Wether it be car tires or pick up tires, regardless of load range, they all pretty much have this type of plies. The stiffness usually associated with E tires is due to the larger amount of rubber in each tire, not it's load range.

There is no such thing as a "10 ply" tire any more (most cases any way), however, there are 10 ply "rated" tires.

35 psi in a P265/75r16 will carry the same load as 35 psi in a LT265/75R16E on a F-150, and vice versa. The tread does not, and will not heat up because the amount of side wall flex is the same between the two tires, and is well with in spec for both tires. Its really simple physics. The difference is that the E tire is rated for psi's up to 80 and the P tire is usually right around 40 max.

What's nice about going with a E tire on a F-150 is that if you want to tow something heavy, you can run the normal psi for every day driving, and then bump the rear up to the max for heavy towing.

 

I would have to disagree about the difference in load ratings. I have had F150s that had load range C OE tires. Pressure was always marked at 36. I have also had F150sthat came with load range D tires OE. Tire pressure was always 40. I have also used Load range E on a vehicle that had as OE load range C. I found that the best pressure to run was 50, for ride and wear. Didn't wear on the outside or inside of the tread.
Take a look at this site. The Feds are proposing minimum pressure activation of tire pressure monitors. Pressures are different by load range.
http://www.unece.org/trans/doc/2004/...-56-inf17e.ppt

ps 1psi = approx 7kpa

 

Like I said earlier, it has to do with different models, i.e. different payload ratings and trailering capacities have to do with the difference in tires, so that the vehicle can use the full capacity of its rating. I can see that I may have muddled that up in my last post.

The tire's load range it self has nothing to do with the psi that is required for proper vehicle handling (also taking into account blow outs), other wise there would be a minimum psi rating and with the max rating. This is where the vehicle mfg's reccomendations come in.

You should never, ever put a tire on that is below the mfg's reccomendation, but going over that requirement (load range ratings) does not automatically mean that you "have" to increase psi to as load range increases. By going with those higher psi's you change the vehicle handling for the worst.