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Old 11-20-2012, 10:30 AM   #1
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Tire pressure - what am I missing??

Really confused here by the tire pressure tables, my weight and load capacities....

I have 2004 Seabreeze, class A model 1341 gas MH. Has Ford chassis. GVWR is 22,000. Empty is 17,300, my weights ready to go are 6375 front and 12,365 rear. Not much gear and don't keep tanks full...anyway, here come questions.

Per Goodyear load chart 245/70r19.5 manufactured after 2006, single load rate at 90 psi is 3890 and dual at 90 psi is 3655, so front load at 90 psi is 2X3,890=7,780!!! and rear is 4X3,655=14,620!!

So if I am reading right, even at 90 psi, these tires are way over where I need to be, and over the GVWR for vehicle, which is 7,500 front axle and 14,500 rear axle.

When I bought this the tires were at 105 PSI and ride was very harsh, I had alignment, balance (Fronts) and shaved to correct out of round, lowered tires to 90 PSI and ride was improved tremendously.

Should I actually lower the pressure below 90 psi, or just keep them there for a safe margin, lowering to 85 would give me 7,480 front and 14,060 rear, still good margin and still very close to GVWR, 21,540 vs. 22,000, and maybe a little better ride.

Curious where you have yours or what you think here.

Many thanks, and Happy Thanksgiving
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Old 11-20-2012, 10:38 AM   #2
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I would stay at 90 psi. Went through 3 MH and never had a problem with 90. Tires wear even and as you have already found out you get a better ride.
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Old 11-20-2012, 10:39 AM   #3
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trode sounds like you have a good understanding of tire psi chart for your rig. With those wts 85 psi will work fine and will improve your ride. good luck and happy rving.
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Old 11-20-2012, 10:49 AM   #4
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If you do drop below the recommended 90 PSI I would highly recommend TPMS. Also I think if you drop to 85 you should be fine because once tires heat up they will be above 90. However I would stay as close to 90 as you can if possible.
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Old 11-20-2012, 11:02 AM   #5
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Without individual wheel position weights you'll want to allow a little more margin in case you have an imbalance side to side. My practice is to go with the pressure from the charts plus 5 psi. The extra gives me a bit of margin so I don't have to worry about dropping below the required minimum with change of temperature, etc. I also monitor my pressure in all tires with a TPMS (PressurePro).
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Old 11-20-2012, 09:07 PM   #6
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I think you are still fine at 85 psi - plenty of margin to allow for side-to-side imbalance or some extra weight onboard. But nothing wrong with staying at 90 either.

Nothing says front and rear axles have to use same psi, so feel free to adjust them separately. Just make sure all the tires on one axle have the same pressure.
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Old 11-20-2012, 10:28 PM   #7
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I run at 85 psi and also run with a TPMS. This last week I had the "pleasure" of driving through the midwest just as that nasty cold front came through. Adjusted my pressures to ~90 psi at end-of-day temps and that gave 85 psi at morning cold temps (25F - brrr). Running pressures then increased to ~98 psi. Typical and consistent with previous experience. I REALLY like the peace of mind the TPMS gives....
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Old 11-20-2012, 10:38 PM   #8
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Quote:
Originally Posted by adehaan86 View Post
If you do drop below the recommended 90 PSI I would highly recommend TPMS. Also I think if you drop to 85 you should be fine because once tires heat up they will be above 90. However I would stay as close to 90 as you can if possible.
You do not worry about 'running PSI'. ALL PSI's are set 'cold'. If you try to set the PSI so it matches the charts recomedation for 'cold', you will actually be UNDERinflated.
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Old 11-20-2012, 10:40 PM   #9
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Originally Posted by Gary RVRoamer View Post
I think you are still fine at 85 psi - plenty of margin to allow for side-to-side imbalance or some extra weight onboard. But nothing wrong with staying at 90 either.

Nothing says front and rear axles have to use same psi, so feel free to adjust them separately. Just make sure all the tires on one axle have the same pressure.
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Old 11-20-2012, 10:41 PM   #10
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Originally Posted by MN_Traveler View Post
I run at 85 psi and also run with a TPMS. This last week I had the "pleasure" of driving through the midwest just as that nasty cold front came through. Adjusted my pressures to ~90 psi at end-of-day temps and that gave 85 psi at morning cold temps (25F - brrr). Running pressures then increased to ~98 psi. Typical and consistent with previous experience. I REALLY like the peace of mind the TPMS gives....
Again, do NOT try to adjust PSI by running temps. ALL PSI's are set 'cold'...
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Old 11-20-2012, 11:05 PM   #11
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Let me be clear: with my weights my cold pressures (by the charts) ARE 85 psi. I simply meant that before I went to bed (with "cold" tires set at 90 psi, but not as cold as morning temps) when I verified in the morning, I hit the 85 psi cold target ( lucky guess). If I had not hit that, I would have adjusted appropriately. I ABSOLUTELY agree that you should not adjust pressures at running temps to the chart pressures: if you do you will be under inflated. Per my TPMS my running pressures are easily 15-20 (or more) psi above the cold set point. Sorry for any confusion.
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