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The sticker on the inside of the Motor Home says the cold tire pressure on the front tires as well as the rear duals is to be 90psi, but on the tires it says 110 cold pressure. This is a 2015 Motor Home bought new with the proper tires on it.

 

I have the TireMinder set up so can see the PSI as well as the temperature of the tires as we drive so know and see they get up to over 110 starting from a cold 90psi, We have put on over 6,000 miles with no indication of improper tire inflation or issues.

 

I am just wondering why the difference between the Tire manufacturer 110psi and the Motor Home Manufacturer 90psi, anyone know?

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The PSI stamped on the tire is the MAXIMUM tire pressure for that tire, not, necessarily, the *best* tire pressure for the weight they are carrying.

 

Until such time as you can have your motorhome weighed (each tire position is ideal, but at least each axle), and then compare those weights with the tire manufacturer's inflation table, use the tire pressure printed on the sticker inside the motorhome. That tire pressure *should* be enough to handle the GAWR of each axle.

LindaH
2014 Winnebago Aspect 27K
2011 Kia Soul

 

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Look at the wording on the tire again. It says pressure for MAX Load or something similar.

The actual weight on each tire is what you are trying to match and the tire manufacturer should have a chart somewhere listing the appropriate pressure thru a range of loads.

The data plate on the vehicle is a good start but you may load your vehicle in a way that puts more load on one axle and or one tire.

Always weight the vehicle fully loaded to ensure you are within safety limits.

I usually take mine with the toad on to a weigh station on the way to the campground with full fuel and half a tank of water.

I talk t the scale operator and we weight the front wheels on the scale, the RV on the scale but not the toad, then everything on the scale.

That gives me front axle weight.

A little math and I deduct the front axle weight from the whole RV weight too give me the rear axle weight.

The everything on weight is the GCVW.

This doesn't give you individual tire weights but lets you know if you are within limits on the axle weights on the data plate or in the owners manual.

Dividing the axe weights by 2 gives you a ballpark wheel weight but it can be off due to uneven loading (Although RV's an be uneven side to side empty due to the location of the fridge etc).

Smart=Weigh the SKP's system for weighing individual wheels is the only real way to know exactly but you can get close using the above method.

Be very attentive to tire pressures, an exploding tire is more excitement than you need.

BnB

2009 Monaco Cayman DP 38'

bnbrv.blogspot.com/

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The sticker on the inside of the Motor Home says the cold tire pressure on the front tires as well as the rear duals is to be 90psi, but on the tires it says 110 cold pressure. This is a 2015 Motor Home bought new with the proper tires on it.

 

I have the TireMinder set up so can see the PSI as well as the temperature of the tires as we drive so know and see they get up to over 110 starting from a cold 90psi, We have put on over 6,000 miles with no indication of improper tire inflation or issues.

 

I am just wondering why the difference between the Tire manufacturer 110psi and the Motor Home Manufacturer 90psi, anyone know?

Your correct tire inflation pressures are always going to be what is on that "sticker", unless you change tires to another size that uses another inflation chart. Or, you're correcting an over-weight condition with tire inflation instead of balancing your cargo load.

 

Airing tires to the load carried is not a FMVSS standard, it's a trucker's standard and it's results are strewn all across our highways and byways.

38' fiver - Dodge Dually

AKA: FastEagle

USN Retired - DOD Retired - SSA Retired

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The tire pressure on the vehicle sticker is recommended by the manufacture based on many hours of vehicle testing and engineering studies as required by FMVSS. This tire pressure has produced the best ride performance and handling along with the best tire and powertrain wear. If you change the tire size or change the vehicle weight substantially, then it may make sense to adjust the tire pressure. Trailer tires are a different issue.

Greg

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Those inflation/load charts are misunderstood by many folks. They all show the absolute minimum air pressure to safely support the corresponding load. As LindaH said, it is not the best/optimum pressure. Michelin, Goodyear, Firestone, etc say to never run less than the mfgrs tire placard recommended air pressure.

The RMA = Rubber Manufacturers Association, published this 66 page pdf, that states on page 51:

"

However, never use inflation pressure lower than
specified by the vehicle tire placard, certification
label or owner’s manual. Nor should inflation
pressure exceed the maximum pressure molded on

the tire sidewall"

Some prefer to sacrifice tire safety and longetivity in search of a softer ride. Goodyear states on their website:

"Tire pressure should never be reduced below the vehicle manufacturer's recommended levels to support load conditions in order to improve the ride quality of a vehicle. The difference in ride quality is not significant. When minimum inflation pressure requirements are not met, tire durability and optimum operation can be affected".

 

Ford tried to use a lower air pressure to obtain a softer ride in the Explorers years ago, we saw the results of that.

 

Bottom line, inflate to mfgrs. tire placard in the vehicle.

 

2000 Winnebago Ultimate Freedom USQ40JD, ISC 8.3 Cummins 350, Spartan MM Chassis. USA IN 1SG retired;Good Sam Life member,FMCA ." And so, my fellow Americans: ask not what your country can do for you--ask what you can do for your country.  John F. Kennedy 20 Jan 1961

 

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The tire pressure on the vehicle sticker is recommended by the manufacture based on many hours of vehicle testing and engineering studies as required by FMVSS. This tire pressure has produced the best ride performance and handling along with the best tire and powertrain wear. If you change the tire size or change the vehicle weight substantially, then it may make sense to adjust the tire pressure. Trailer tires are a different issue.

Greg

 

 

I agree for passenger tires this is a valid statement. But I truly doubt RV manufactures are doing anything more then CYA and setting the PSI usually at a higher PSI then the tire manufacturer would feel is needed. I understand this, as they are not our driving for hundreds of thousands of miles to test the optimum PSI setting. I've always felt it was best to do the SmartWeight (Or some other mentor of Four Corner weight.) and setting the tires PSI to the Tire Manufactures Load Ratings PSI value. I personally take the recommended PSI for the weight, and add 10% contingency on top of this, rounding up to the next '0' or '5' setting. (IE: 85PSI + 8.5 (10% of 85) = 93.5PSI. I round up to 95PSI) The 10% contingency allows for weight creep while traveling, and some as you travel PSI lossage without having to find a compressor large enough to reset your PSI levels. We did about 10K over 5 months on our trip to Alaska in 2014. Only had to top up a few PSI at the end of this trip.

 

Until you have a Four Corner weight, yep, run with he placard's values.

 

And of course, opinions do vary on PSI:)!

 

Best to all, travel safe, have fun,

Smitty

Be safe, have fun,

Smitty

04 CC Allure "RooII" - Our "E" ride for life!

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I agree for passenger tires this is a valid statement. But I truly doubt RV manufactures are doing anything more then CYA and setting the PSI usually at a higher PSI then the tire manufacturer would feel is needed. I understand this, as they are not our driving for hundreds of thousands of miles to test the optimum PSI setting. I've always felt it was best to do the SmartWeight (Or some other mentor of Four Corner weight.) and setting the tires PSI to the Tire Manufactures Load Ratings PSI value. I personally take the recommended PSI for the weight, and add 10% contingency on top of this, rounding up to the next '0' or '5' setting. (IE: 85PSI + 8.5 (10% of 85) = 93.5PSI. I round up to 95PSI) The 10% contingency allows for weight creep while traveling, and some as you travel PSI lossage without having to find a compressor large enough to reset your PSI levels. We did about 10K over 5 months on our trip to Alaska in 2014. Only had to top up a few PSI at the end of this trip.

 

Until you have a Four Corner weight, yep, run with he placard's values.

Smitty and I are on the same page with this one. The only way to know for sure what tire pressure is best is to use the tire manufacturer's inflation charts, based upon the actual weight on each wheel when loaded for travel, which you get from SmartWeigh or some similar service. Also remember that you go by the heaviest tire one each axle and always inflate both tires on one axle to the same pressure. If you do not have access to individual wheel weights, the next best thing is to go to any truck scale that gives you individual axle weights and use that (divided by half for each tire) but in such case I would also bump it up by about 20% to be sure since the two sides seldom weigh the same. In addition, most tire experts suggest that when using the actual weights, you need to run the inflation 10% over the chart just to insure that the tire will never be under inflated. There is more danger in an under inflated tire than in an over inflated one.

 

Running tires at the maximum inflation pressure from the sidewall will typically mean over inflated and that gives you a stiffer ride and will cause tires to wear more in the center of the tread than they do on the outer edges. Under inflation tends to wear more on the outer edges but either will cause poorer handling and uneven tire wear.

 

The tire pressure in the RV is based upon the original tires supplied by the factory and is based upon designed weights and not actual ones. Until you can get actual weights and with the OEM tires still on the RV, I would use the listed inflation, plus 10% until I had the opportunity to get the individual axle weights when loaded, or better yet, the individual wheel weights when loaded.

Good travelin !...............Kirk

Full-time 11+ years...... Now seasonal travelers.
Kirk & Pam's Great RV Adventure

            images?q=tbn:ANd9GcQqFswi_bvvojaMvanTWAI

 

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All RV tires, fitted to Motor Homes and RV trailers are done so by their manufacturer as directed in Federal Motor Vehicle Safety Standards.

 

After market replacement tires are fitted by the retailers using tire industry standards that also follow the guidelines of the FMVSS.

 

Because the largest RV trailers and almost all Motor Homes use some form of medium to heavy truck tires, some regulations from the trucking industry (FMCSA) may have been mistakenly deemed applicable for those type tires when fitted to RVs. Those regulations do not have a provision for establishing recommended cold tire inflation pressures.

 

Does the vehicle you recommend to have their tires inflated to the load carried have a vehicle certification label depicting recommend cold tire inflation pressures?

 

The FMVSS in part says to never use less tire inflation pressures than what is on the certification label. That’s for normal everyday uses. Exceptions will be outlined in the vehicle owner’s manual.

 

Because tires fitted to automotive vehicles may have generous load capacity reserves via tire inflation they may be inflated to their maximum load capacity via the reserve inflation values. That is not considered over-inflation. But, is it needed for a vehicle/axle overload condition? The RMA recommends reducing your cargo loads and balance the remainder to alleviate the overloading.

 

FMVSS 571.120 will explain tire fitments and cargo capacities.

 

The reference provided below has a section for inflating RV tires. It’s from a tire manufacturer that has had problems with NHTSA in the past and their stance on tire inflation may be reflective of the results.

 

https://toyotires2-1524598101.netdna-ssl.com/assets/lib:toyo%20content/RV_tire_safety.pdf

38' fiver - Dodge Dually

AKA: FastEagle

USN Retired - DOD Retired - SSA Retired

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I agree for passenger tires this is a valid statement. But I truly doubt RV manufactures are doing anything more then CYA and setting the PSI usually at a higher PSI then the tire manufacturer would feel is needed. I understand this, as they are not our driving for hundreds of thousands of miles to test the optimum PSI setting. I've always felt it was best to do the SmartWeight (Or some other mentor of Four Corner weight.) and setting the tires PSI to the Tire Manufactures Load Ratings PSI value. I personally take the recommended PSI for the weight, and add 10% contingency on top of this, rounding up to the next '0' or '5' setting. (IE: 85PSI + 8.5 (10% of 85) = 93.5PSI. I round up to 95PSI) The 10% contingency allows for weight creep while traveling, and some as you travel PSI lossage without having to find a compressor large enough to reset your PSI levels. We did about 10K over 5 months on our trip to Alaska in 2014. Only had to top up a few PSI at the end of this trip.

 

Until you have a Four Corner weight, yep, run with he placard's values.

 

And of course, opinions do vary on PSI:)!

 

Best to all, travel safe, have fun,

Smitty

Smitty, that is true for RV/MH tires according to Goodyear and the RMA.(click on the links I provided, and the link tirehobby provided for proof)

 

2000 Winnebago Ultimate Freedom USQ40JD, ISC 8.3 Cummins 350, Spartan MM Chassis. USA IN 1SG retired;Good Sam Life member,FMCA ." And so, my fellow Americans: ask not what your country can do for you--ask what you can do for your country.  John F. Kennedy 20 Jan 1961

 

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The Winnebago sticker lists the pressures needed for the RV if fully loaded to the GVWR (gross vehicle weight rating) for that particular RV.

If you are not loaded to capacity you can reduce the pressures to match the actual weight. This may improve the ride.

The following is what Michelin says about it in their RV Tire Guide.

 

HOW MUCH AIR SHOULD I CARRY IN MY TIRES?
The amount of air pressure you need to use depends on the weight of your fully loaded
vehicle. So, you cannot determine your correct air pressure unless you know your vehicle‘s
actual weights. If you look at your tire‘s sidewall, you’ll see the maximum load allowed
for the size tire and load rating, and the minimum cold air inflation needed to carry that
maximum load. The lower the air pressure, the lower the load you can carry. A complete
load and inflation table is available at www.michelinrvtires.com.

Clay(WA5NMR), Lee(Wife), Katie & Kelli (cats)
Full timed for eleven years in our 2004 Winnebago Sightseer 35N Workhorse chassis. Snowbirds for 1 year. Now settled down in western CO.
Honda Accord toad.

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Michelin also says this in the reference provided.

 

“The vehicle manufacturer selects the size and type of tires for their vehicles. They perform the necessary testing to establish the vehicles’ optimized operating tire inflation pressures which can be found on the vehicle placard (located on the inside of the driver's door) and in the vehicle owners’ manual.”

 

“If the tires on your vehicle are the same size as the original equipment tire, inflate them to the pressures indicated on the placard.”

 

http://www.michelinman.com/US/en/help/faq.html

38' fiver - Dodge Dually

AKA: FastEagle

USN Retired - DOD Retired - SSA Retired

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  • 1 month later...

Do most truckstops still have air hoses that are free? I've seen the 'pay' for air smaller ones, but I can't get my 5th wheel up next to the buildings to use those.

Welcome to the Escapee forums! Always a good thing to see new members join us here and I do hope that you become a regular.

 

On the free air hose, it has been some time since I spent much time in the truck stops since we downsized to our current travel trailer but I don't recall having seen one recently. Because I carry an air compressor with me in the RV, I seldom have any need to use one of them. :)

 

If you don't get many responses to this, you may want to try asking again by starting a new thread since not everyone reads new posts to past threads.

Good travelin !...............Kirk

Full-time 11+ years...... Now seasonal travelers.
Kirk & Pam's Great RV Adventure

            images?q=tbn:ANd9GcQqFswi_bvvojaMvanTWAI

 

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OK I'll be the Devils advocate here. How much do you trust what the builders say re anything? How many trailers and 5th wheels over the years have had issues with tires. How many motorhomes come off the production line with little or no carrying capacity? And you trust what they say re tire pressures!!

 

My advice? Ask someone who knows. And that's not me. But if it was me I would be close to the MAX air pressure. Especially in summer with hot roads.

 

Get it weighed and ask a tire professional.

 

regards

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