Tire Pressure Chart

[LOG]

Originally Posted by FastEagle

The vehicle certification label on every vehicle, most often referred to as "that little yellow sticker", is a valid sworn statement by the vehicle manufacturer. it says, in part, That "This vehicle conforms to all applicable U.S. Federal motor vehicle safety standards in effect on the date of manufacture shown above".

Your choice as a vehicle owner/consumer is to stay within those safety parameters. When an owner/consumer knowingly exceeds the minimum safety limit they commit a safety violation that only they are responsible for.

All I do is provide awareness of the regulations/standards as they appear in various publications.

For this post I am using a Ford E450 Motorhome Chassis. The tire placard on a Ford E450 shows 65 PSI Front and 80 PSI rear. The front GAWR is 4600 lbs and the rear GAWR is 9450. The 65 PSI front and 80 PSI rear are the PSI required to support the GAWR ratings.
The reference you provided states on page 44 "never use inflation pressure lower than specified on the vehicle tire placard, certification label or owner's manual." It also states on page 44 "The Gross Axle Weight Rating Vehicle (GAWR) or The Gross Vehicle Weight Rating (GVWR) must never be exceeded." Then on page 45 it states "The actual or calculated weigts can be compared to the GAWR, GVWR and tire capacities. The weights also help determine the proper tire inflation pressure for the tires."
This is after it explaines how to weight the RV.
Since the tire pressure can not be lower than the tire placard. And the GAWR and GVWR can not be exceeded. And the tire pressures are already at the minumum PSI for the GAWRs. And the rear tires are already at the maximum cold PSI of 80, why would anyone ever weigh a Ford E450.
And why would that article go to that much print to explain weighing the RV?
And, I would like to point out that the source of that article is not a standard or regulation. It is simply an association of tire manufactures. No weight of law, regulation or otherwise. Opinions and recommendations, like yours or mine.
I would also point out that the Michelin RV brochure provides that the RV should be weighed and the tire inflation charts be used to determine the correct tire pressures for the loads they are carrying. They also are not a regulation.

[LOG]

Originally Posted by FastEagle

There is no provision in FMVSS that will allow tire inflations below what was recommended by the vehicle manufacturer. Unless, an additional tire load inflation placard was provided with the vehicle or in the vehicle owner manual.

Is there a provision that disallows tire inflations below what is recommended by the vehicle manufacturer?

Do you actually think that Michelin would publish a brochure that explains how to weigh a RV and then use their inflation tables on how much air to put in the tires, if it was against federal regulations.

[LOG]

The Federal Regulations for tires are found at 49 CFR 393.75. I quote from 393.75 (I) Tire Inflation Pressure (1) "No motor vehicle shall be operated on a tire which has a cold inflation pressure less than that specified for the load being carried".

[Bill Gail]

I'd like to start by thanking everyone for their participation in this thread .
I feel we have resolved the tire pressure to load issue .
I set my tire pressures to F / 55 , R / 60 based on my certified scale weights and the Toyo tire pressure chart. So the only change was to the front tires where I conservatively when 10 lbs above the chart recommendation and 10 lbs below the door placard.
I noticed what I felt was more control in the steering , the light / loose feeling was dampened .
I felt a big improvement in going over Freeway Expansion Joints the bang and jarring was significantly reduced as well as less side movement from passing semi's .
Thanks again guys .

[FastEagle]

Originally Posted by LOG

For this post I am using a Ford E450 Motorhome Chassis. The tire placard on a Ford E450 shows 65 PSI Front and 80 PSI rear. The front GAWR is 4600 lbs and the rear GAWR is 9450. The 65 PSI front and 80 PSI rear are the PSI required to support the GAWR ratings.
The reference you provided states on page 44 "never use inflation pressure lower than specified on the vehicle tire placard, certification label or owner's manual." It also states on page 44 "The Gross Axle Weight Rating Vehicle (GAWR) or The Gross Vehicle Weight Rating (GVWR) must never be exceeded." Then on page 45 it states "The actual or calculated weigts can be compared to the GAWR, GVWR and tire capacities. The weights also help determine the proper tire inflation pressure for the tires."
This is after it explaines how to weight the RV.
Since the tire pressure can not be lower than the tire placard. And the GAWR and GVWR can not be exceeded. And the tire pressures are already at the minumum PSI for the GAWRs. And the rear tires are already at the maximum cold PSI of 80, why would anyone ever weigh a Ford E450.
And why would that article go to that much print to explain weighing the RV?
And, I would like to point out that the source of that article is not a standard or regulation. It is simply an association of tire manufactures. No weight of law, regulation or otherwise. Opinions and recommendations, like yours or mine.
I would also point out that the Michelin RV brochure provides that the RV should be weighed and the tire inflation charts be used to determine the correct tire pressures for the loads they are carrying. They also are not a regulation.

Is your E450 a pick-up truck or a E450 chasse carrying a final stage RV?

Even though the FMVSS (standards) are identical for trucks and RV trailers there is a difference in tire/axle fitments. The standard clearly directs the vehicle manufacturer to provide tires that equal the load capacity of the vehicles certified GAWRs. However, for automotive vehicles there is a provision that stipulates automotive vehicles must be fitted with tires/axles that provide a percentage of load capacity reserves. That does not apply to RV trailer axles. If your axles total GAWR has a percentage of load capacity in excess of the vehicle GVWR, the tires only have to equal the load capacity of the GAWR. If the GAWRs equal the vehicle GVWR, the tires MUST provide the predetermined load capacity reserves. How do we get load capacity from our tires? Inflation pressures. Who sets those inflation pressures? The vehicle manufacturer. How does the vehicle manufacturer determine their recommended cold inflation pressures for those tires? By using TRA validated tire industry load inflation charts.

The USTMA has said in their document to never use less tire inflation pressure than what has been recommended on the vehicle certification label. they don't have to repeat it over and over again, once was enough.

Tire industry standards work hand and glove with the governing body regulations. Therefore, the USTMA is justified in saying not to use less than what's been recommended by the vehicle manufacturer. Why? FMVSS are written to insure minimum safety standards have been applied to insure all automotive safety standards for your vehicle have been met on the day of final manufacture. Therefore, the recommended cold inflation pressures for your vehicle tires is deemed a minimum standard and is supported as such in all industry documents.

[FastEagle]

Originally Posted by LOG

The Federal Regulations for tires are found at 49 CFR 393.75. I quote from 393.75 (I) Tire Inflation Pressure (1) "No motor vehicle shall be operated on a tire which has a cold inflation pressure less than that specified for the load being carried".

An often misuse of that regulation. The FMCSA (commercial trucker) regulations are not applicable with FMVSS standards.

Actually the FMVSS says the same thing about the load being carried, just in a different way. The automotive industry requires a percentage of load capacity reserves above the load carried. It is also a minimum standard for the auto industry.

[FastEagle]

Originally Posted by LOG

Is there a provision that disallows tire inflations below what is recommended by the vehicle manufacturer?

Do you actually think that Michelin would publish a brochure that explains how to weigh a RV and then use their inflation tables on how much air to put in the tires, if it was against federal regulations.

Are you familiar with the term, "set the class level"?

Michelin documents assume you already know the vehicle manufacturer's recommended cold inflation pressures for vehicles built under the guidance of FMVSS are minimum standards.

Michelin also assumes all of their commercial truck tires are being used on commercial vehicles which allows inflate to the load carried.

I talk with them often. I live 10 miles from Michelin of North America (Greenville, SC).

[Bill Gail]

Originally Posted by FastEagle

Is your E450 a pick-up truck or a E450 chasse carrying a final stage RV?

Even though the FMVSS (standards) are identical for trucks and RV trailers there is a difference in tire/axle fitments. The standard clearly directs the vehicle manufacturer to provide tires that equal the load capacity of the vehicles certified GAWRs. However, for automotive vehicles there is a provision that stipulates automotive vehicles must be fitted with tires/axles that provide a percentage of load capacity reserves. That does not apply to RV trailer axles. If your axles total GAWR has a percentage of load capacity in excess of the vehicle GVWR, the tires only have to equal the load capacity of the GAWR. If the GAWRs equal the vehicle GVWR, the tires MUST provide the predetermined load capacity reserves. How do we get load capacity from our tires? Inflation pressures. Who sets those inflation pressures? The vehicle manufacturer. How does the vehicle manufacturer determine their recommended cold inflation pressures for those tires? By using TRA validated tire industry load inflation charts.

The USTMA has said in their document to never use less tire inflation pressure than what has been recommended on the vehicle certification label. they don't have to repeat it over and over again, once was enough.

Tire industry standards work hand and glove with the governing body regulations. Therefore, the USTMA is justified in saying not to use less than what's been recommended by the vehicle manufacturer. Why? FMVSS are written to insure minimum safety standards have been applied to insure all automotive safety standards for your vehicle have been met on the day of final manufacture. Therefore, the recommended cold inflation pressures for your vehicle tires is deemed a minimum standard and is supported as such in all industry documents.

Here's my take on the matter.

Obviously the way the "legalize" is used , the Regs are open to interpretation .
The second to the last sentence in the last paragraph sums it up .

(FMVSS are written to ensure minimum safety standards have been applied to ensure all automotive safety standards for your vehicle have been met ON THE DAY OF FINAL MANUFACTURE)

I interpret that to mean the vehicle needs to be delivered in a condition that meets all design maximum loads ,this is because they have to assume the purchaser will immediately use the vehicle to it's maximum ratings.

Nothing more , nothing less .

In fact , there is a statement that the tires should never be run over pressure due to potential damage from road hazard due to the tires inability to flex and absorb impacts .
I interpret that to apply to tires run at pressures higher than necessary for the actual applied load.

FWIW

[LOG]

Originally Posted by FastEagle

.

The USTMA has said in their document to never use less tire inflation pressure than what has been recommended on the vehicle certification label. they don't have to repeat it over and over again, once was enough.

.

Will you will please just provide the Federal Regulation (law) that supports the statement in the quote above.

[LOG]

Originally Posted by FastEagle

In the reference attached below, scroll down to page #44 and read the information in the paragraphs under the header - Determining Proper Inflation Pressure.

Bottom line; never use inflation pressures below vehicle manufacturer recommendations.

https://www.ustires.org/sites/defaul...TruckTires.pdf

It appears that the publication you have referenced is for vehicles with a Gross Vehicle Weight Rating (GVWR) of 10,000 lbs or less.
Please refer to page iii "Purpose'.
Let us know what you find out.

[FastEagle]

Originally Posted by Bill Gail

Here's my take on the matter.


I interpret that to mean the vehicle needs to be delivered in a condition that meets all design maximum loads ,this is because they have to assume the purchaser will immediately use the vehicle to it's maximum ratings.

Ask NHTSA.

https://isearch.nhtsa.gov/

The FMVSS is very straight forward and really not open to intreptutation in application.

With tire fitments for RV trailers the manufacturer has two options. Fit tires to the certified axle that provide a load capacity that will support the axle. The reference below shows just how blatant the trailer manufacturer can be with that application.

Further on in the same standard the manufacturer is directed to set a recommended cold inflation pressure that is appropriate for the tires to support the certified loads. Those are MINIMUM standards. You may read it as a vehicle manufacturer covering his position and you're correct in that assumption, because if they don't use those minimum standards, a NHTSA recall action will force them to do it. A monitory NHTSA penalty for forced recalls can be substantial, equaling thousands of dollars for each vehicle in violation.

https://www.keystoneforums.com/forum...pictureid=6489

Do the math; vehicle certified axles 5080# -- Original Equipment tires will provide 2540# ea. at 65 PSI.

Over the years I have taken pictures of hundreds of vehicle certification labels. Before 2016 the action in the one above was commonplace. It caused a lot of tire failures blamed entirely on the tires.

[FastEagle]

Originally Posted by LOG

Will you will please just provide the Federal Regulation (law) that supports the statement in the quote above.

The tire industry has no choice but to follow government minimum regulations. Those regulations are binding on the vehicle manufacturer and are passed on when the vehicle is first sold.

In short, the vehicle manufacturer has set a recommended cold inflation pressure they deem appropriate for that fitment. That action has set the minimum inflation pressures for that vehicle and all subsequent replacement tires.

NHTSA allows auxiliary tire placards to display replacement tire designated size when it differs from the OE size. A new recommended cold inflation pressure will be established that will allow the replacement tire to provide a load capacity equal to or greater than the OE tires and displayed on the auxiliary placard.

[FastEagle]

Originally Posted by LOG

It appears that the publication you have referenced is for vehicles with a Gross Vehicle Weight Rating (GVWR) of 10,000 lbs or less.
Please refer to page iii "Purpose'.
Let us know what you find out.

That's okay because FMVSS 571.110 & 571.120 both say the same thing.

[LOG]

Originally Posted by FastEagle

With tire fitments for RV trailers the manufacturer has two options.

I believe this is a Class C Motorhome forum. Please provide an example for a Class C Motorhome from the hundreds of photos you have taken.