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Thread: Cooper H tire inflation
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07-03-2020, 09:41 AM #1
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Cooper H tire inflation
Hi all - I'm kinda confused on the correct tire pressure I should be using. Tires are Cooper Roadmaster RM170 215/75R17.5. During my PDI, the dealer said inflate to 110psi. Now checking the Roadmaster website and I'm seeing some conflicting info. I realize I should have each tire weighed separately to know the true weight at each position, but for this discussion let's simplify it and say the MAX load on any one tire would be half of the 7K axle rating = 3500lb. Again, ignoring the pin weight for this discussion. . . .
I found a chart online that says for these tires, the MAX load for dual tires is 4540 @125psi (obviously not loading these tires that much):
Then I found another chart that indicates for 3500lb load, the pressure should be 90psi:
Knowing that I should be loading each tire well below the 3500, doesn't this indicate that even 90psi is too much?
Thanks for the help!2021 Solitude 310GK: Linen/DP windows/gen prep/slide toppers/king bed/EOH disc brakes/Cooper-H tires
2019 F-350: Lariat/CC/LB/Diesel/DRW/4x4/Bakflip MX4/B&W 20K/AirLift 5000
Other stuff: TST 507 TPMS/2x BB batteries/Victron BMV-712/Champion 3500 dual fuel gen/Garmin 780 GPS/22" Blackstone
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07-03-2020, 09:45 AM #2
What does the sticker say on the side of your trailer?
Rob & Nikki + Cloverfield
2020 Grand Design Solitude S-Class 3350RL
2015 RAM 3500 Longhorn Laramie Crew Cab, Long Bed, 4x4 Dually Cummins/AISIN
Mountains of Pennsylvania
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07-03-2020, 09:56 AM #3
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2021 Solitude 310GK: Linen/DP windows/gen prep/slide toppers/king bed/EOH disc brakes/Cooper-H tires
2019 F-350: Lariat/CC/LB/Diesel/DRW/4x4/Bakflip MX4/B&W 20K/AirLift 5000
Other stuff: TST 507 TPMS/2x BB batteries/Victron BMV-712/Champion 3500 dual fuel gen/Garmin 780 GPS/22" Blackstone
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07-03-2020, 10:16 AM #4
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Steve and Renee
2018 Solitude 310GK, disc brakes, Morryde SRE4000/XFactor with heavy duty shackles
2012 Ram 3500 SRW 6.7 Diesel, air bags
18k B&W Companion, non-slider
640 watts solar, 400 amp-hour Lion Safari UT 1300 battery bank
Aims 1500 watt inverter/charger with ATS
Somerset, WI
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07-03-2020, 10:19 AM #5
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You highlighted the dual application number. The tires on our trailers are not used dual - that's where wheels are mounted in pairs like on the rear axle of our trucks. You should use the "Single" numbers. That said, I would probably stick with the 110 PSI on the trailer sticker as mentioned by @geotex1 .
RobU.S. Army Retired
2012 F350 DRW CC LB Lariat PS 6.7
2020 Solitude 310GK-R, MORryde IS, disc brakes,
Sailun LRG tires, solar, DP windows, W/D
(Previously in a Reflection 337RLS)
Full time since 08/2015
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07-03-2020, 10:27 AM #6
My recommendation is that you call GD. The tire pressure placard is NHTSA-mandated and promulgated in the CFR. However, I don't know the intricacies of its application to RVs or repercussion for OEM mismatch. Obviously consumers can deviate after the sale.
Rob & Nikki + Cloverfield
2020 Grand Design Solitude S-Class 3350RL
2015 RAM 3500 Longhorn Laramie Crew Cab, Long Bed, 4x4 Dually Cummins/AISIN
Mountains of Pennsylvania
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07-03-2020, 11:50 AM #7
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Thanks everyone - I really appreciate your feedback! I sent messages to GD, my dealer, and Roadmaster Tire. I don't expect any quick replies due to the holiday - I'll start calling on Monday. 110psi seems to make the most sense.
2021 Solitude 310GK: Linen/DP windows/gen prep/slide toppers/king bed/EOH disc brakes/Cooper-H tires
2019 F-350: Lariat/CC/LB/Diesel/DRW/4x4/Bakflip MX4/B&W 20K/AirLift 5000
Other stuff: TST 507 TPMS/2x BB batteries/Victron BMV-712/Champion 3500 dual fuel gen/Garmin 780 GPS/22" Blackstone
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07-03-2020, 10:07 PM #8
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Your setup is different than mine (I have the Dexter 8k axles with the 215/75R17.5 Cooper H Roadmasters and my GVWR is 18,000), but for what it’s worth, my sticker specifies 125 psi cold and that is what we are running. No problems so far. TST TPMS tells me that Solitude tires are all running right at 140 psi when warmed up. All good, and rides very well.
Home is where you park it!
2021 Solitude 380FL
2014 Silverado 3500HD LTZ DRW 6.6L Duramax Allison 6 Speed
RVing since 1996; Full Time since 2018
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07-09-2020, 06:08 PM #9
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To make a long story short, the GD rep in our area advised on the direction of the production manager that I should be running 120psi since that's probably what the rims are good for. Where do I find the rim pressure rating? Do I need to remove the wheel and look at the back side? Thanks!
2021 Solitude 310GK: Linen/DP windows/gen prep/slide toppers/king bed/EOH disc brakes/Cooper-H tires
2019 F-350: Lariat/CC/LB/Diesel/DRW/4x4/Bakflip MX4/B&W 20K/AirLift 5000
Other stuff: TST 507 TPMS/2x BB batteries/Victron BMV-712/Champion 3500 dual fuel gen/Garmin 780 GPS/22" Blackstone
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08-21-2021, 11:26 AM #10
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There is no need to run 125 psi unless your tires are carrying the maximum of 4805 lbs per tire. Use the Cooper Roadmaster tire inflation chart to determine how high your pressure should be. To determine your axle weights go to a Cat scale & weigh each axle. As an example my 345 GK front axle is 6420lbs & rear axle is 6340lbs. If each tire on the axle is carrying the same amount of weight the tires on my front axle are each carrying 3210lbs. Using the chart I only need to run 75 psi. I want an extra safety margin so I’m running 90 psi. I’ve attempted to attach the chart but if it’s not there you can google the chart for Roadmaster 170 M tires. The tire is listed as a pickup & delivery tire and trailer tire. If the attachment did not load I would appreciate a quick tutorial on attachments to posts. Overinflating your tires makes the trailer bounce a lot more & potentially wears the center of the tire quicker.
Ray & Flo
2021 Silverado 3500HD DRW
2021 Solitude GK345-R
Morryde IS & Disc Brakes
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