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Old 07-19-2016, 09:12 AM   #11
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Originally Posted by etex211 View Post
The vehicle manufactures put lots of R&D hours into determining the optimum tire pressure for a vehicle. The weight of the vehicle, the quality of the ride, the handling, and the fuel mileage are all considered.

On a pickup, the recommended tire pressure for the rear assumes the truck is loaded to capacity, so you are actually better off running a lower pressure when the vehicle is unloaded.

Running unnecessarily high air pressures will compromise the vehicle's handling and can cause you to lose control.

My recommendation is to follow the manufacturers suggested air pressures. If you've upgraded the tires to a higher load range, then you have the ability to raise the air pressure when you pull the trailer, and then return the air pressure to normal when the trailer is unhitched.
The engineering work is based upon the specific tires mentioned on the yellow sticker. When you upgrade tires, rims and other suspension components you have no basis to claim partial compliance with the yellow sticker. Data and outcomes change when one variable is changed. Until I test my changes, and they are my changes, I cannot predict an outcome by partial compliance with other variables.
The best answer is be safe and use common sense.
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Old 07-19-2016, 09:20 AM   #12
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Originally Posted by eldermike View Post
The engineering work is based upon the specific tires mentioned on the yellow sticker. When you upgrade tires, rims and other suspension components you have no basis to claim partial compliance with the yellow sticker. Data and outcomes change when one variable is changed. Until I test my changes, and they are my changes, I cannot predict an outcome by partial compliance with other variables.
The best answer is be safe and use common sense.
While I agree with you, unfortunately common sense and the general public's knowledge of how to fill a tire are rarely in sync. Based on the small number of responses, and those who are recommending to inflate to the sidewall rated pressure (which is MAX pressure, not recommended pressure for those who don't know), it appears that common sense is not all that common.
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Old 07-19-2016, 09:36 AM   #13
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When you change the LR of the tire, it changes the whole equation. The sticker is no longer valid and you have to take the info provided on the sticker and transpolate it to new information for that new tire.

If you don't do that, who knows whats happening.
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Old 07-19-2016, 11:48 PM   #14
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You need to weigh the front and rear axle at a scale and determine the load on each tire. Then use this formula:

Per tire weight divided by max tire weight(3415 lbs) x max tire pressure(80psi) = inflated tire pressure.

This is the formula I use on my 2500 Dodge with E-rated tires. I'm currently running about 48psi front and 37psi rear with a light load in the back. Running too high pressures especially in the rear of a light weight pick-up will cause the center of the tires to wear prematurely.
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Old 07-20-2016, 07:52 AM   #15
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Quote:
Originally Posted by jasoncw View Post
While I agree with you, unfortunately common sense and the general public's knowledge of how to fill a tire are rarely in sync. Based on the small number of responses, and those who are recommending to inflate to the sidewall rated pressure (which is MAX pressure, not recommended pressure for those who don't know), it appears that common sense is not all that common.
Max tire pressure is related to max load rating. After thinking about this thread a bit I think it's time to introduce the idea of load as our focus when questions come up concerning tire pressures.

I run my E's at 65lbs per the yellow sticker on my F350 DRW. That works fine on the DRW setup. When I owned a F250 SRW I ran E's at max pressure based on load when towing.
Disclaimer:
Running 80psi when unloaded is not safe for people that don't understand the dynamic changes that occur in the suspension of your truck based upon tire pressure per loading. Your tires will bounce/rebound much better than OEM tires/pressures allow when adding pressure without adding load. The footprint is changed/reduced by increasing pressure without increasing load, and this reduces traction/friction. Add these two changes together and then introduce some rain on the road and you are now driving a vehicle of your own design and your own responsibility. If you do not understand these owner introduced limitations then do not stray far from the yellow sticker on your vehicle.
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Old 07-20-2016, 08:09 AM   #16
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I'm lucky. I just leave my tires at 50 psi front and 55 psi rear. My current trailer is relatively light, 4950# gvwr.

But of course that's the air pressure Ford calls for on the yellow sticker. My truck came with OEM LT E tires.

My previous truck, 2005 F150, came with P tires. The max pressure on the side wall was 44#. Yellow sticker was somewhere in the 30's. When I was towing with those tires, I did inflate the tires up to 44 psi. Otherwise, I left them at the yellow placard psi number.
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