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chompchomp

Port Orange, Florida

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Posted: 07/17/20 05:50pm Link  |  Quote  |  Print  |  Notify Moderator

I have an Itasca Sunova 35j, and posted on the driver's side of the coach it says 80 psi cold all tires. I have 6 19.5 Michelins and on the sidewall it's stamped 120 psi cold. I've always split the difference on the road. If we're at 100 psi all around, we're rolling.

I'm just curious how the rest of you navigate that; I mean 40 psi is a big discrepency. Thanks for any feedback.


2008 Itasca Sunova 35J Motorhome
2003 Jeep Wrangler X Toad
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jdc1

Rescue, Ca

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Posted: 07/17/20 06:41pm Link  |  Quote  |  Print  |  Notify Moderator

The engineers that designed that RV probably know more about this than anyone on this site.

MountainAir05

New Mexico

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Posted: 07/17/20 07:05pm Link  |  Quote  |  Print  |  Notify Moderator

The higher # is with max weight. The 80 is a number to start from. Weight it and you should be around 85+. Higher numbers are just a harsh ride and tire wear in the center. Our 37.3 same tire weight to how we travel was 85 to 90.

STBRetired

I-80 and I-55

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Posted: 07/17/20 07:15pm Link  |  Quote  |  Print  |  Notify Moderator

Weigh it at a CAT scale then look up the numbers on the Michelin site for how much air to put in each tire based upon the weight it has to carry. Make sure all your tanks are filled like they would be for you when you are traveling. Get in all the people and their stuff for the weigh in. I run 88 in the front, 92 in the rear based upon my traveling weight and the Michelin tire pressure charts.

Edit: The people who make your tires know the most about how much air to put in them.


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enblethen

Moses Lake, WA

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Posted: 07/17/20 07:15pm Link  |  Quote  |  Print  |  Notify Moderator

You need to weigh your rig with it loaded for the road then use chart for inflation level. I run my tires, not Michelins five pounds over the correct inflation chart for my tires.Michelin RV inflation chart


Bud
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rk911

DuPage County

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Posted: 07/17/20 07:20pm Link  |  Quote  |  Print  |  Notify Moderator

chompchomp wrote:

I have an Itasca Sunova 35j, and posted on the driver's side of the coach it says 80 psi cold all tires. I have 6 19.5 Michelins and on the sidewall it's stamped 120 psi cold. I've always split the difference on the road. If we're at 100 psi all around, we're rolling.

I'm just curious how the rest of you navigate that; I mean 40 psi is a big discrepency. Thanks for any feedback.


the 120-psi on the tire is the maximum pressure the tires are rated for. and while you can inflate them to the max the result may be a very hard ride along with possible handling issues.

the 80-psi on your placard may be the optimal air pressure for the RV's weight when it left the factory or for the GVWR (gross vehicle weight rating) of the MH. using this air pressure will result in a much better ride but it still may be too low or too high for your MH's actual weight.

the proper way to determine the correct pressure for each tire is to load the MH as you would for a trip and then take it to a certified scale to get weighed. loading includes full fuel, lp and fresh water tanks, food, clothing, supplies, pets, people and other stuff. individual corner weights are best but indiviidual axle weights will do. once you know the axle weights and have compared those weights to the published GAWR (gross axle weight rating) for your MH (to be certain neither axle is overweight) consult the Michelin tire inflation guide (available online). this will show the correct inflation for the weight you're carrying for the tires on that axle.

you can add any amount you like to the recommended pressure up to the tire's max. some folks add 5-10 PSI for peace of mind, some don't. you can add but you can't subtract, the rule is....inflate to the minimum pressure for the load being carried.


Rich
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2016 Itasca Suncruiser 38Q
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CapriRacer

Somewhere in the US

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Posted: 07/18/20 05:39am Link  |  Quote  |  Print  |  Notify Moderator

chompchomp wrote:

I have an Itasca Sunova 35j, and posted on the driver's side of the coach it says 80 psi cold all tires. I have 6 19.5 Michelins and on the sidewall it's stamped 120 psi cold. I've always split the difference on the road. If we're at 100 psi all around, we're rolling.

I'm just curious how the rest of you navigate that; I mean 40 psi is a big discrepancy. Thanks for any feedback.


Are the tire sizes the same? I almost sounds like the original tires - the ones listed on the vehicle tire placard - were 235/85R16 Load Range E (80 psi max). If that is the case, then those 19.5's are probably an upgrade.

Oh and a Rule of Thumb: You don't want to get more than a 10% increase in pressure between cold and running. If you get more, then you need to slow down and think about getting tires with more load carrying capacity. (Maybe that's what happened here?)

If you get 15% or more, you need to take immediate action. Slow down AND get tires with more load capacity - within a week!


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wa8yxm

Wherever I happen to park

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Posted: 07/18/20 06:13am Link  |  Quote  |  Print  |  Notify Moderator

There are 3 pressures all but guaranteed to be wrong. IN the OP's case they are
80 PSI (The sticker) 120 PSI (The tires) and the pressure the tire store put in.

The proper pressure is kind of complex to figure out for many (Easy for me) but
You need wheel weights. Each wheel ideally (NOTE Duals are one wheel) Two ways to get this

Method one: A segmented scale. one axle per segment Total axle weight
Then pull on again but only one side on the scale NOTE this has to be a FLAT scale not a bridge type. Now you have weights on one end of the axle. subtract from total axle to get the other side.

Option two https://rvsafety.com/
Then click on the RV-Weighing tab on the right.

IN option 1 you download the tire inflatio chart from the tire manufacturer and work it out

In option 2 you tell them what tires you have, and they show up with the proper chart in hand. They figure it out for you and provide some basic education.

..
Why is proper inflation important?

Well if the pressure is too low then sidewalls flex excessively, over heat and BANG. if you do not know how to control a vehicle with sudden tire failure you are dead.. In any case major damage may happen.

You also have reduced control

IF over inflated the tire wears only in the center. the Ride is rougher and again there is loss of control

Proper inflation means the tire life is maximized and so is control.


Home is where I park it.
Kenwood TS-2000 housed in a 2005 Damon Intruder 377


IB853347201

Eastern Ontario

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Posted: 07/18/20 06:39am Link  |  Quote  |  Print  |  Notify Moderator

rk911 wrote:

the 120-psi on the tire is the maximum pressure the tires are rated for. and while you can inflate them to the max the result may be a very hard ride along with possible handling issues.

the 80-psi on your placard may be the optimal air pressure for the RV's weight when it left the factory or for the GVWR (gross vehicle weight rating) of the MH. using this air pressure will result in a much better ride but it still may be too low or too high for your MH's actual weight.


I would not overthink this. if the manufacturer specs 80-psi, go with 80-psi. Your handling will improve dramatically. Currently with your tires set at 100-psi, i'll bet the back end wanders all over the road and the handling is exhausting.


Touring in our 2010 Suncruiser, beaches, site seeing, national parks, chillaxing..

hipower

Western PA

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Posted: 07/18/20 07:05am Link  |  Quote  |  Print  |  Notify Moderator

After reading numerous threads on this subject over the years I wonder how many people put this much effort into finding and maintaining the pressure in the tires on our cars, suvs and pickup trucks?

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