I believe inside the door it says to fill the tires up to 35 lbs psi max, my tires say 80 lbs psi should I only fill my tires up to 35 lbs?

 

the proper way to figure your correct air pressure is this,... ready,....

1)weigh the front axle, record the weight
2)weigh the rear axle, record the weight.

now this is where it gets tough, the maxium weight a tire can allow at (in your case) is 80PSI, at lets say maximum weight of 3500lbs, so it says on the tire something like this, "Max load 3500lbs @80PSI Single" now remember, times 2 for two tires on an axle

If your front axle weighed 4000 pounds you would take 4000lbs times 80PSI divided by 7000lbs to get your air pressure which would be 45.7 PSI. The 7000 came from 3500lbs/tire times 2 tires

*** these are just figures to help show you the math*****

my 2000 F350 Diesel dually 4X4 when I bought new tires I told them what to use for air pressure ( I ran a tire service truck for 12 years)

my fronts were 52 PSI and the rear duals were 28 PSI. Now the truck was not loaded, different when you add a load. I had 54,000kms on those tires and still had about 60% left.

Get your weights and we can tell you what pressure to run.

My 2001 7700 4X4 LT245 75R 16 with 8 ply tires (load range D) runs 41 PSI in front and 38 PSI in the rear ( I had 2 natural gas tanks where the spare was) with the 5th wheel 38 PSI in front and 49 PSI in rear.

notice the front axle weight went down with the 5th wheel on, that is because I had the 5th wheel hitch slide back behind the axle centerline meaning less weight on the front axle.

Hope you were able to follow this

Rob/HBT

usually tire pressures on a VIN plate are an approximate but when extras are added or load ranges are changed, you have to recalculate the pressures

 

I have Goodyear Wrangler MT/R's 10 ply and it says 80psi. I run them at 50psi.. and that's what the tire shop who put them on put them at..

I guess I do not know the proper way of inflating my tires to the correct psi. I have heard of the different psi in front and rear but never understood it. Shop said if I tow, put them at 60psi, if I offroad drop them to 40psi.

I was just talking to my buddy about checking my tires and making sure they are at 50psi. He told me, PUT THEM AT 35PSI! That's what your door jam says. And I told him my tires are different and has a max of 80psi. He told me it doesn't matter......

If I had them at 35psi I would get such bad gas mileage..

 

AXFX4, tell your friend, it does matter what tires you have on your truck. Each truck is different weight wise and tire load ranges affect this.

So what if he put a set of "P" 245/75R16 on a truck that requires "LT"/245 75R16. Door VIN says 50 PSI and the tire he put on is Max 35 PSI????? A ruined set in no time, "oh but it doesn't matter" It does, when you pay $700-$1000 for a set of tires that give you 20,000 miles and the centers are wore right off, I've seen it


If a tire was to run under inflated and the outsides are wore down, then you have to over inflate to even out the wear. If a tire is cupping it takes too long to try and even out the wear. That is why tires are rotated so often. Tire shops have an idea on what to run and they usually get it in the ball park so to speak but the proper way for the tire to last alot longer, is proper inflation and regular rotations, front to back only to prevent radial pull. Tires don't separate anymore from side to side rotations.

just my 2 cents worth anyhow, and I'll shut up now

Rob/HBT

 

^ Hey you learn something every day.

Could you explain why you have different PSI ratings in the front vs the back? I do 50psi all around.. but that's just what the shop put in and said keep it at.

I guess if I did the weight on front axle vs back axle..

 

you got it right AZFX4 ,

The front axle usually weighs more than the rear axle on a pickup because of the extra weight of the engine, ESPECIALLY the diesels. My 7700 front axle is 3306lbs and the rear 3086lbs for a total of 6393lbs and that is with 2-300lb naturalgas (CNG) tanks where the spare usually is and 2 adults and 2 kids in the truck I run 41PSI in front and 38PSI in the rear. the tires are Load range "D" (2623lbs @ 65PSI) Door VIN says 50 PSI.

with the 5th wheel loaded with water and hooked up, I had 50 PSI in the rear. Now imagine what the tires would look like if I ran 50PSI empty...........

Rob/HBT

 

I have the toyo AT tires and located their tire inflation chart that specifies air pressure vs load. Anyhow I was trying to estimate the weight on each axle of my f150 as I do not have access to a scale. It is a 2wd 5.4 extended cab, 2000 and is typically loaded with only about 200 pounds in the back as well as about 400 in the cab. The truck is about 4600 lbs empty so total weight is about 5200 loaded. I would think there is a lot more weight on the front axle. Any guesses on front and rear axle weight? Thanks.

 

no sorry, with guessing weights, this formula is out the window.

I had my truck towed on a flat bed last year (parkbrake pads let go and made a terrible sound) When the guy was loading it he asked me what was in the truck that made it so heavy. He had a 1 ton with a winch deck and when the truck was being loaded, it lifted his front wheels off the ground. I told him nothing, he called bull***t and had to check for himself. He couldn't believe an F150 was that heavy

Rob/HBT

 

well what size tire are you running? something like a 265/75/16 is stock for 3/4 ton trucks and have a heavier load rating so they normaly have a psi of 70-80, if you have an aftermarket size then you should probably do what hit-by-thunder said and do all of the calculations. but if it is the same size tire as what came on it stock then i would go 35 psi unloaded, and 50 when loaded. or ask the dealer you got the tires from they should have inflated them to the right psi when they gave the truck to you

 

I got the wheels and tires used, but only about 2k on the tires. They are

285/70R17 2105lbs@35 psi, 2315lbs@40psi, 2510lbs@45psi, 2755@50psi.
I also bought the truck used, came with 265/65/17s.
On the door sticker it states 3100 gvw for the front and 3500 gvw for the back axle so probably ok at 35psi.
Probably will just try 35-40 psi in the front and 35 psi in the rear since weight distribution is probably 60/40 or worse.
Yes surprising how heavy the 2wd extended cab f150 is.