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Old 06-21-2021, 07:21 AM   #1
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Tire Pressure when Pulling 5th Wheel Question

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?
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Old 06-21-2021, 07:51 AM   #2
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Remember that 3375Lbs is divided between the four tires.
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Old 06-21-2021, 08:00 AM   #3
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We are pulling a 35' Montana with our 2018 F350 dually and run the same door sticker specs in the tires.
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Old 06-21-2021, 08:58 AM   #4
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Remember that 3375Lbs is divided between the four tires.
Are you sure? When we had our 5er just for kicks I stopped by some of the open scales scattered throughout Oregon and weighed my setup. Weight on the front axle never changed. I only saw increases on the rear axle. The front only went up because of my DW and I sitting in the front seat.
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Old 06-21-2021, 09:28 AM   #5
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Are you sure? When we had our 5er just for kicks I stopped by some of the open scales scattered throughout Oregon and weighed my setup. Weight on the front axle never changed. I only saw increases on the rear axle. The front only went up because of my DW and I sitting in the front seat.
He said he had a Dual rear wheel (4 tires)
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Old 06-21-2021, 09:47 AM   #6
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OP ...you have a Dually
Therefore you need to check tire inflation charts that list Single AND Dually PSI

Your chart is Single only.....80# would be correct but not for dually

Your Tire Data Sticker states 65#...that is MAX for each tire on rear axle

Pin wet PLUS trucks Rear Axle weight....total weight being carried by Rear axle/Tires DIVIDED by 4 equals tire load
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Old 06-21-2021, 10:03 AM   #7
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I have a 17 F350 dually. I run 75 PSI in the front and 65 PSI in the rear. i pull a 41 ft fifth wheel with 2730 lbs of pin weight. I put all my tires to 80 PSI. Big mistake. It chucked real bad and bounced all over the road. I put the tires back to F 75 and R 65 PSI and it tows great.
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Old 06-21-2021, 11:57 AM   #8
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I have a 17 F350 dually. I run 75 PSI in the front and 65 PSI in the rear. i pull a 41 ft fifth wheel with 2730 lbs of pin weight. I put all my tires to 80 PSI. Big mistake. It chucked real bad and bounced all over the road. I put the tires back to F 75 and R 65 PSI and it tows great.
Might want to check that pin weight
2015 Sierra 375RKS
Dry weight 12,396 with Dry Pin 2906
GVWR 15500 WET pin at 20% (low %)...3100
*Dry Ratio is 23%.......so Wet pin at 23%=3565

Your posted pin is less then DRY pin MFG lists



Regardless....OP ---65# rear tires on that dually
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Old 06-21-2021, 12:10 PM   #9
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X2 on that. Also if you use it a lot not pulling drop pressure to 50 or 55. I like to drive thru water standing and stop when existing. You will see your tires footprint. You want the entire tire contact on the highway.
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Old 06-21-2021, 01:05 PM   #10
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X2 on that. Also if you use it a lot not pulling drop pressure to 50 or 55. I like to drive thru water standing and stop when existing. You will see your tires footprint. You want the entire tire contact on the highway.
That's easier then sidewalk chalk mark across threads
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Old 06-21-2021, 07:02 PM   #11
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My dually with 3900 pin weight, 70lbs front 65lbs rear.
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Old 06-22-2021, 05:22 AM   #12
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Thank you everyone, sounds like I just need to follow the PSI values listed on the Tire and Loading Information sticker on my truck, Front: 75psi Rear: 65psi
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Old 06-22-2021, 10:25 AM   #13
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Originally Posted by Old-Biscuit View Post
Might want to check that pin weight
2015 Sierra 375RKS
Dry weight 12,396 with Dry Pin 2906
GVWR 15500 WET pin at 20% (low %)...3100
*Dry Ratio is 23%.......so Wet pin at 23%=3565

Your posted pin is less then DRY pin MFG lists



Regardless....OP ---65# rear tires on that dually
Good point. I called Forrest river about my dry pin weight before I bought the fifth wheel. Dry on my sticker was 11870 lbs and the dealer said the listed pin weight was 1900 lbs. Forrest river confirmed that the brochure was incorrect. It should have said 1900 lbs which is still light. I went to the scales and my fifth wheel weighed 12900 lbs and my pin was 2500 lbs 19%. Now after a few years I have scaled it 3 times more I have 2730 lbs of pin weight and it weights 10300 lbs on the axles. I added slide toppers and shift more stuff to my fwd compartment and added 230 lbs to my pin. I am at 20.5 % right now.
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Old 06-22-2021, 06:37 PM   #14
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2017 F350 dually, door sticker says max for the vehicle is "easily" handled with smooth sailing at 70 front and 65 rear..... who can argue? I agree the scale ticket did not change on the front loaded/unloaded! I wonder why they went to 75 PSI on the fronts after the first initial production 2017?
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