I have a 04 screw lariat with rugged trail bf goodrich tires.I just recently inflated the tires to mfr recommendation of 35 psi.Since then i have noticed that they ride harder and personally i like the ride better when they were at 30 psi.I don't do any towing at all.Would it be ok to keep them at a lower 32 psi for the winter or even lower?

 

ahsi,

About a year ago there was a thread on tire pressure. It lasted for about six pages, and got very emotional. The prevailing advice was to stick to the pressure Ford advises, unless you change to a completely different type of tire.

With that said; here's my opinion. I don't present my opinion as fact. The previous thread did tend to convince me that optimum tire pressure is a subject better listed under the black arts than any simple scientific measurement. But I am convinced that it's better to increase pressure slightly than to decrease it.

1. Increasing tire pressure 2 - 5 PSI will give a stiffer ride with better handling and cornering. It may also increase mileage and tire life. Ford seems to recommend 7 - 10 PSI below the tire manufacturer's max rating, so a 2 - 5 PSI increase should be safe. More than 5 PSI is getting into areas that I don't advise.

2. As noted above, Ford seems to recommend pressures a little on the low side, probably in order to provide a smooth ride. Going below this recommendation is very likely to adversely affect handling, mileage, and tire life. I don't think that reducing pressure by 3 PSI will be dangerous, but I certainly don't recommend it.

3. When in doubt, give a little credit to the Ford engineers that made the recommendation.

 

I'm assuming that the ford f150 tire pressure recommendation is the same if you have maximum payload or when the truck bed is empty.Was this by design?I think they just did not do the testing to determine the appropriate tire pressure in different conditions.My wifes car has different recommendations depending on just 2, or 4 passengers and/or how much baggage you have in the trunk.Does this make sense and do you think this should even be an issue?

 

Tire pressure can cause as many arguments as brand of oil.
Ford does know what your tires pressure should be set for load. Because of two factors, they aren't going to talk about it.

1. Liability. It ain't worth the risk that you will lower your tire pressure for cruising the city, then forget and dump sand in the back, spill it on a turn and blame Ford.

2. It's too complicated for the average driver. They might have said, If all you do is cruise, no weight in bed, you might lower your tires 3-4 lbs in rear, 1 lb in front. When you load the truck, bring it up to stock, when you highway at high speeds increase it 2 lbs over stock. But who would do that? Who would always set it cold, not hot? Temps make it vary up to 10 lbs.

These are normal instructions for working trucks. They expect you to know what your doing when you buy utility trucks.

They expect a slightly stupid, uneducated grandmother to buy our trucks, and not get confused.

Most important, Do you have any clue how close your Tire Pressure gauge is?
I use the averaging method. I have over two dozen gauges of high quality in my gauge drawer (not a collector, spent many years selling autoparts, sampled all gauge types, brands.) The spread in reading across high quality gauges is 8 lbs at 35.
Yes, that's 30-38 pounds on the same tire. Using average, tossing out best and worst, I have four or five gauges that read within a half pound of accurate.
Park the truck outside, and measure the tires at 10 in the morning, the sun side tires are 1.5 lbs higher than the shade side. Measure the tires at 40 degrees, vs. 90 degrees, both at 10 in the morning, one fall, one late fall, and the pressure is 4 lbs difference.

If you want to devote a bit of time, money and most important THOUGHT to your tires, you can improve you ride, or your mileage by playing with the pressure. But no 'quick rule of thumb' will do it. If you don't want to mess with multiple gauges, temp checks etc. use the stock settings.
Chris

 

It would be safe to run them with 32lbs but your fuel economy would be affected.

 

I have mine set at 32psi, 35 psi is MAXIMUM, I have been told by the front end man at my Ford dealer that 30 would be the minimum. Look at it this way too, picture teh "I" as teh ground and the "(" and the ")" as the tire shape. More air pressure will make the tire like this I-(, less air pressure will make the tire like this I-). Too much psi and the centers of the tires wear fast, too little and it wears the edges quicker. Look to get your tired where they are I-I. Do it on concrete and get tires where they are flat on the ground and not I-( or I-).

Also more PSI will make truck ride rougher but will increase mpg's slightly, less psi will make truck ride softer but will decrease mileage slightly.

 

Increasing your tire pressure can greatly increase your mileage. And decrease your safty and ride quality. Oldest tune up trick in the world is to over inflate the customers tires, his car seems quicker, his mileage shoots up. His car may 'skitter' on corners, and bounce on speed bumps, but that's not what you worked on, right?
If your are trying for mileage, and don't mind a rougher ride, an extra 1-2 lbs over max will deliver. Safty might drop a little. You pays your money, you takes your choice.

So said, over inflated is probably a lot safer than underinflated, which rides smooth, handles poorly, get rotten mileage, etc.
Over inflation burns the center of the tire, underinflation burns outer edges.
Probably 32-36 is barely noticable on ride, handeling on our trucks. I like 34 front, 32 rear as I seldom carry much weight. 36-7 all the way around gets another half mile to the gallon, but on local roads that are as bad as ours, it's not worth it.
Chris

 

I keep my tires at 40psi. The tire maker recommends a max of 44psi cold.

Personally, I think Ford's recommendation of 35psi is too low, but that's just me.

 

if i keep mine at fords recommended numbers the tires look flat they look like fat innertubes.

 

I leave them at 35 most of the time, but confess to going with 38-40 on long highway trips. They still wear great at slightly higher, and I have gotten as much as 3 mpg better with several trucks doing this. On a 2000 mile trip that translates to about 17 gallons less gas used. At an average central coast price of 2.25 gal, this would save $38!

 

275 x 65 x 18" Rugged Trails are rated at 2365lbs@35psi.


Ok in theroy....

Truck weighs 5500lbs. That would be roughly 1375lbs on each tire, but the truck is heavier in the front than the rear. Lets call that a 55/45 split. 55% is roughly 3000lbs on the front tires and 2500lbs on the rear tires.

Now if you take 2365 and divide it by 35 gives you 67.5lbs. Means each 1psi you have in the tires will carry 67.5lbs of weight. 1500lb on each tire divided by 67.5, 22psi in each tire should be enough air to carry the front end. 1250lb each on the rear tires they only need 18.5psi to carry the load.


Now we all know that's not going to work, but as an example it's easy to see the tires have way more capacity than the truck weighs empty.

There shouldn't be a problem running the front tires at 30psi and the rears at 25psi. Thing is it may not be safe. Not only will the MPG suffer, handling, but if you were forced into situation where the truck was sliding sideways it would lots more prone to tripping and flipping over. The softer tire would have more grip in a direction you don't want.


I used to run the "E" rated 80psi tire under my F250 at 50 up front and 40 in the rear. 80psi all around was crazy, you could roll over a quarter and tell if it was heads or tails. Running 50-60% air in those is not the same as these 35lb tires.


My BFG's RT's are wearing great with 32psi in them. I was at the dealer the other day for an oil change. They go over the whole truck. The measured the tread depth. Both fronts have 17/32" tread left and the rears 13/32" left...at 4200 miles..... Better good HUH??? Except the tires new only have 13/32" of tread. The boneheads........ I need to pickup the tire tread depth indicator anyway...


A tire tread depth indicator is the only way to chech and watch your tread wear. You can buy them ay any auto parts store for 4-5 bucks..

 

I used to race gas RC cars and have a hand held heat gague...I ran the truck hard and took a temp reading across the tire. I also ran some chalk lines across the tire. After screwing around I found that unloaded my nitto 325/60/18 are pretty good at 38 front and 32 rear..My rims are 9" wide...I am sure people with the stock rims running these tires will have hotter center tire reading and will have to run less air.

 

You guys seem to forget, that less PSI will produce more heat on the tire. Heat will destroy a tire. I recommend you stay with the factory specs.

 

Most know that when a tire is run it gets warm, thus increasing tire presure..All tires should be checked and adjusted while cold. On a hot summer day your tire pressures will increase quite a bit.. Ford and others try and find a mid point but your environment will determine the right cold readings. I wonder if you filled your tires in Alaska on a -25 degree day and drove to Florida into an 85 degree day how much higher you pressures yould be?

 

Well said hovy:
I run my tires at 32 psi because by the time they heat up they are around normal (35psi).