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Old 04-15-2019, 08:14 AM   #1
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90PSI in rears ???

All the tire threads are out of date so I must start a new thread.

I am confused ! Why do people put 90 PSI in their rear dualies ? I am a full timer and carry everything I need so my rears are at max weight and at 110 psi can carry 17,640lbs maximum, but at 90psi only 15,060lbs (that’s 2580 lbs less). The fronts at 110lbs can carry 9350lbs and at 90psi can carry 8280lbs.
You must weigh your unit fully loaded (full fuel, water, load, passengers, etc) and then set the pressure. If your front weight is not at max but the pressure is then the tires are hard and will not give you the handling you want. Did you ever hear people say the front end wanders ? See the attachment.
Thank you for your inputs and safe travels to all.
Attached Files
File Type: doc Tire pressures at weight chart.doc (24.0 KB, 20 views)
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Old 04-15-2019, 08:18 AM   #2
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Country Coach says to always run your tires at the pressure shown on the Federal weight sticker and never reduce it for lower weights. This is in my owners manual and is due to some blowouts with TOYO tires. In fact TOYO put out a letter to their dealers telling them not to install any of their tires on Country Coach motorhomes. As far as I can find out that letter still exists (I did some searches and found it) and is still in effect although dealers ignore it today.
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Old 04-15-2019, 08:23 AM   #3
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Quote:
I am confused ! Why do people put 90 PSI in their rear dualies ?
Answer #1: Because that is the correct amount for their axle weight and tire size.

Answer #2: Because it says 90 psi on the sidewall

Answer #3: Because some other RVer they know of uses 90 psi

Answer #4: The guy at the tire shop said so


Answer #1 is correct; answers #2-#4 are mistakes.
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Old 04-15-2019, 08:33 AM   #4
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correction

Site put wrong attachment, this is one I wanted.
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Name:	RV tires inflation pressure.JPG
Views:	39
Size:	194.3 KB
ID:	242080  
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Old 04-15-2019, 09:47 AM   #5
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Because you can never be sure that you are at the exact weight that you have inflated it for. It doesn't make sense to me to do something like set your tires up to carry a reduced capacity and risk overloading them. Sometimes one over zealous shopping trip at a stop somewhere can put you overweight. So why risk it? It's free to fill them up all the way yet can cost a ton of cash and leave you stranded in some unknown spot at possibly a bad time, if your wrong.


I run all my tires at full sidewall pressure, plus I rotate and balance them very often and I get crazy longevity from that. I watch them closely for any possibly issues. I look at them all at least one time a day. I kick the duals at least once a day as one can mask a low tire. I had 90k miles on a set with tons of meat left on them on one truck I sold.
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Old 04-15-2019, 10:31 AM   #6
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Quote:
Originally Posted by Gary RVRoamer View Post
Answer #1: Because that is the correct amount for their axle weight and tire size.

Answer #2: Because it says 90 psi on the sidewall

Answer #3: Because some other RVer they know of uses 90 psi

Answer #4: The guy at the tire shop said so


Answer #1 is correct; answers #2-#4 are mistakes.
Ding, Ding, DinG, DiNG, DING!!!!! Agree that #1 is the winner...

Travel safe, have fun,
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Old 04-15-2019, 10:49 AM   #7
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Yup agree w #1
The tricky part it define the "correct" pressure.
If you do 4 corner wts it's easy it's the higher driver or passenger side of front & rear.
More difficult is if you only do axle wts.
Best practice to add 10% to avg to allow for side to side variation or
Some use avg and then add 5 psi as a safety factor.
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Old 04-15-2019, 11:01 AM   #8
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You can either air your tires for the load you carry or air them to some higher pressure for the load you might carry in the future. Either method will work fine.

Just don't try to carry more weight than you have aired the tires for.

If you have no idea what you weigh, then air them up to their max capacity, cross your figures and hope for the best. This is by far the worst method.
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Old 04-15-2019, 03:50 PM   #9
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The thing that amazes me about all this is how many people are reluctant to spend 5 minutes and $12 to get axle weights on a CAT scale.
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Old 04-15-2019, 04:11 PM   #10
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I put 90 in my rears because my coach does not weigh what the sticker says. Altogether my coach is 5,000 less than the label. Only lower the pressure if you know the weight and add a little for safety.

Low pressure causes the tire to heat and that is far more dangerous than the loss of traction an excessively hard tire might have.

I also like a smooth ride, hard tires are hard and also impact the suspension more than a tire that will absorb small impacts.
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Old 04-15-2019, 06:17 PM   #11
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I run 95 in the front and 90 in the rear because that's what the manufacturer of my tires says to run for the weights on my axles.
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Old 04-15-2019, 06:27 PM   #12
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Quote:
Originally Posted by Gary RVRoamer View Post
Answer #1: Because that is the correct amount for their axle weight and tire size.

Answer #2: Because it says 90 psi on the sidewall

Answer #3: Because some other RVer they know of uses 90 psi

Answer #4: The guy at the tire shop said so


Answer #1 is correct; answers #2-#4 are mistakes.

^^ This
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Old 04-15-2019, 06:38 PM   #13
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When I first bought my unit, it had 120psi in the rears and 110 in the front and that's what I was told to maintain. OK, if you say so... I had my unit weighed shortly after I first purchased it. Once when fully loaded and with full tanks all around (just because, I wanted to know it's max weight and it was right at the sticker rating...) and once with our "normal" load plan with full fuel, full propane, about 10 gallons of water for emergencies and the rest empty, plus my wife, dogs and all our gear and food. After doing so I felt like I knew more than I had before, but was still curious and learning every day. I looked up information on Michelin's website and found that my pressures were too high for my load! I dropped 'em to 85 all around, as suggested by their charts, and was amazed at the difference in ride AND handling! Smoother, quieter, quicker response and truer handling. It's good to be curious...

Interesting thing happened the next time I bought new tires... Michelins from Pomptons, to replace the Goodyears on the coach before. They put 85 psi in them. I asked why and whether it was because that's what I had the old ones at. He laughed a bit and then explained that's where they should be based on my weight and the tires. He couldn't care less how my old ones were pressurized, but I should keep them at 85 unless my load changes appreciably. At that point I decided not to ask if he'd weighed the coach or just guessed "that's about what all these RV's weigh..." and left a happy camper. All good!

Best to you!
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Old 04-15-2019, 06:39 PM   #14
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I'm trying to figure out whether you think 90psi is too little, or too much ?
I have a tag axle coach, and only need 85psi in my drive axle tires.

Ok, now I have re-read your original post, you have little wee tires and 110psi is max.
You better check and make sure your rear axle can handle 17600 lbs . My gasser MH had a 14 or 15,000 lb rear axle.
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