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Rhagfo · 06-22-2021, 09:13 PM

Quote:

Originally Posted by DMacLeod

I have an F350 Dually with LT245/75R17E 121/118R tires and a Grand Design 397TH with a hitch weight of about 3,375lbs. The sticker inside the trucks driver side door shows the front tires should be set to 75 PSI cold and the rear tires set to 65 PSI cold. I found a chart that shows the tires could be inflated up to 80 PSI to support the additional weight when towing my 5th wheel. My question is; should I increase the PSI in the rear tires when towing my 5th wheel?

The loading sticker is for the max payload. So think that your rear axle likely has a rating of 9,750#+, what does your rear axle weigh loaded? I have a 2,700# pin so I run about 60 psi in my rears, could likely easily go down to 55 psi without issue.

Skilletface · 06-23-2021, 05:04 AM

Before making any adjustments get an empty weight of the TV and a reweigh with TT connected.
Attached is a weight to inflation chart for your size tires add about %10 to the recommend PSI based on the actual weight.
Using the method stated in post #9, make 2 PSI adjustment down until full tread face contact to the ground is achieved, that will be your inflation sweet spot for your rig. All of these adjustments are to be completed before the vehicle tires get heated up.
By running only the pressure need for the weight being moved, I think your driving experience will improve. Some have complained about wondering and death wobble on Ford trucks for years on my model by lowering the PSI to 55 on the steer axel loaded and empty, well, it tightened the front end up and improved the driving experience.

https://tirepressure.com/lt245-75r17-tire-pressure

tigerGUY · 06-26-2021, 12:47 PM

This is entirely different, but the point is about air pressure measurement. My RotorFlex pin box(by Lippert) failed and Lippert sent me a new Flex Air. Initial trip I inflated the pin box to 75 lbs. Max is 100psi and minimum 40psi. It rode like a buckboard. Shook our rig up pretty bad. I'm going to try 50psi when we leave for Jacksonville next week. This RVer life is about being flexible.