I just bought a set of new BF Goodrich Rugged Trails (LT265/70R17) for my 2005 F-150STX 4x4 and I am having a tough time trying to figure out what psi I should run them at. The good folks at Sears set them at 44psi and they seem to be working well after 2 days. The maximum psi rating on the sidewall is 3195lbs @ 80psi. Any suggestions? I am not concerned with ride quality as a truck is a truck and not a car! Nothing is worse to me than a "mushy" riding truck! What I do care about is treadwear and gas mileage.

Thanks in advance!

 

Run them at 50. 44 is a bit low, although not seriously. I would not run them less than 45-46. I have run that size and load range on an F150 before at 50 with no problems.
On a side note, if that tire came OE on a new vehicle with TPMS, the low pressure warning would go off at 46.

 

Do not go by pressure on the tire that is maximum for the vehicle if you run them that high you're going to wear the centre of the tire out. You should always run the tire pressures at what is listed on the vehicle. should be on inside of drivers door or fuel door sometimes.

 

I was running my MTZs at 50 on my 02 Expedition and wore out the middle faster than the outsides. I took them down to 37 or 38 now and the're riding a lot better. It all depends on what you're using it the truck for. If it gets used for a lot of towing then it's ok to run more air in them.

 

I'd stick with 40 to 45 psi for daily driving.

 

isn't that only for stock tires though? Mine came with 255/70/17, and the sticker says 35psi. my truck has 265/70/17 tires on it, and I took a few pounds out to get them to 35, but now they look a bit under-inflated.

how do you figure out the correct psi for a larger tire?

 

I'm struggling to understand the same thing.

 

Set them at a pressure that you like as far as ride quality. I personally like my ride in a truck to be on the stiff side. Monitor your tire wear. Every 3000-5000 miles, measure the tread on all four tires on the outside edge, center, and inside edge. If both edges are wearing evenly, and wearing faster, increase pressure. If both edges are wearing evenly, and the center is wearing faster, decrease tire pressure. I personally prefer to wear the center slightly faster than the outsides, to the tune of 2/32" throughout the tire life. This leads to better handling, lower tire temperatures, and possibly a slight increase in fuel economy. It also allows for those times when the truck takes on extra weight, whether it be in passengers, gear, or cargo, and tire pressures cannot be corrected or are forgotten completely.

That being said, never go higher than the max pressure spec on the tire's sidewall.

 

that sounds like a good system. I guess there is no easy way to determine the perfect pressure for any given tire on any given vehicle.

 

Good tip and my 2 cents.

Use your chalk (thick chalk- say 1"inch wide of chalk) on all tire (4) cross line (edge to edge) then drive 20-30feet forward if you still see chalk on the edge too much with middle chalk disappear then reduce the 2/3 psi until you see the chalk is almost disappear on the edge of tires then you have a correct psi.

My 295 terra, front 42, rear 40.

YOMAN!

 

As far as tire pressure, the size of the tire has little to nothing to do with what air pressure to use. It has just about everything to do with type of tire, metric or flotation, and the load range. And within load range, the max pressures listed on the tire. You would not run an 80 psi LR E at the same pressure you would run a 65 psi LR E.

PS - running below 40 on a LR E tire with a max of 80 on an F150, is a good way to play Russian Roulette. No different than running a p series below 30 on an Explorer. Remember Firestone?