Why not just inflate to the Certification label level?

I continue to read RV forum posts from people asking about what inflation to use. Tire Sidewall?, Sticker? Owner's manual? The inflation used by a neighbor? There is also continued confusion on what the sticker inflation is.

"Vehicle Certification Label" AKA "Tire Placard" only considers one thing. The max tire load capacity (molded on the tire sidewall) when the tire is inflated to the level associated with the original tire Load Range (Ply Rating) as shown in the industry load & Inflation tables.

Federal DOT Regulations specify the label indicate the tire inflation level needed to support AT LEAST  50% of the GAWR. NOTE there is no margin or reserve load capacity specified or required by the DOT Regulations.

Starting in Nov 2017, the RVIA (RV Industry Association) required that trailers have a 10% margin on tire load capacity. Motorhomes do not have this margin requirement from RVIA as far as I know.

This Reserve Load margin for trailers is more important than on Motorhomes due to the significantly higher Interply Shear imposed in trailer application.

Tire companies, do not know the exact loading that will be placed on their tires in RV application so you have to do a little work to learn the MINIMUM inflation needs for your personal vehicle. You could simply use the inflation on the Tire Placard but you still need to confirm, with scale measurement, that no axle is loaded more than the stated GAWR. It is also strongly recommended that you confirm your side-to-side load split is close to 50/50 as the tires do not "know" what the other tires are supporting, so you could be unknowingly overloading one tire by hundreds or even 1,000#.

I have other posts in this blog on how to learn the individual tire loads.

##RVT900

Can't find your Tire Placard? Here is some help.

This post updated 1/5/19 to correct broken link.

As I review various RV forums I occasionally come across special problems. Here is an example:
Originally Posted by J

"I'm new to motorhomes so bear with me. I don't have a sticker on the door jamb to tell what psi is recommended. The tires are 215-85-16, it's an 1988 ford E 350 20 ft. class c. The tires state max psi of 80 but I will have to replace them since I found out they are 10 years old. I wonder if someone could give a recommendation for pressures front & back? Also, a tire shop said I could use LT 245-75-16 instead since they are approximately the same diameter but slightly wider. Just have to make sure they are D or E load rated. I have seen that size on a 16 ft. moving truck before. What say you all?"

While J has the additional problem of not being the original owner so he doesn't have the manuals or original tire info from 1988 he still wants to do the right thing and to use the proper tire inflation for his application. While your size or RV may be different I think that you could follow the info here and resolve similar situation.

Here is what I suggest.

 +++++++

My Class-C is 21' that was also built on a "cut-away van" chassis so we probably have similar weights BUT just because I run xx psi is not the best way to learn what you should run.

I strongly suggest you read this page on tires from the Tire manufacturer's Association
I doubt you have a slide on your Class-C so you are probably reasonably balanced and probably within 48/52% side to side.

With your RV loaded as you would normally travel (Food, fuel, water, people, tools etc) get to a truck scale. Use these links to find nearest to you.

Truck Scales and Weigh Stations Locator for Truck Drivers and Trucking Companies at Truckstops

Locate truck scales, truckstops, truck service centers, and diesel prices

Get the individual axle loads then assume one side has 52% of the load. (NOTE if your RV has slides or is a Class-A you really need to confirm individual corner weights or assume a 45/55% side to side split if you only get individual axle weight readings) Using that load you can use the Load Inflation tables for your brand tire (list on THIS link)

You may be light enough to use LR-D but may find a better selection using LR-E. Either way, find the Minimum inflation that is rated to carry at least the load you calculated for your LT215/85R16 tires.

The LT245/75R16 tires suggested by the salesman needs 11.34" Dual Spacing which is a lot more than your OE LT215/75R16 that only need 9.88". This is the clearance between the center-line of duals and is controlled by the wheels. Tire to tire contact or "Kissing" can lead to tire failure so unless the tire store is willing to put in writing that the LT245's will not have dual spacing issues or they will replace the tires for free, I would stay with your current size.

I suggest your CIP - Cold Inflation Pressure) be the minimum inflation calculated above + 10% so you don't have to worry about the need to add air if there is a big temperature drop. Remember never exceed the "cold" inflation pressure rating for the wheel which should be stamped on the wheel or available from the wheel manufacturer.

For those that don't know "RMA" stands for the Rubber Manufacturers Association. This 100 year old organization represents tire manufacturers that produce tires in the U.S.A. RMA represents its members before federal, state and local government entities; develops safety standards for passenger, light truck and commercial truck tires; advocates for environmentally and economically sound scrap tire management polices aggregates data pertaining to U.S. tire shipments; and, educates consumers about proper tire care, among other activities. They have a number of informative publications available for free on their website.

I think the RMA RV tire guide gives a good overview on tire safety and proper practices.

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How do I know what my hot pressure and temperature should be?

Bill P. asked

“I just read your article on tires and speed. Seems that most RVers would stay around 60 mph here in the USA since it is the best speed for gas economics along with tire wear. That being said I would love to hear your thoughts on tire pressure/temperature monitoring systems. I have a class C 28' Four Winds and as a new person to the RV world purchased a monitoring system.

In my travels I get a variety of readings from tires and sometimes am concerned as to the pressure max and temp max. All six tires are exactly the same but in all my reading I find it impossible to get opinions or facts on what to expect in pressure and temperature from cold temps to normal driving pressures and temps.

I understand there are a lot of factors such as weight of vehicle to the temperature in the area and highway...but there should be something on what the absolute limits above the max cold pressure and possible the same comparison with temperature. I find nothing. Example: I run the duals at between 75 psi to 80 psi and 80 is the max at cold. Does this tire allow the pressure to rise up to 90 or even 100? If you need the tire size and weight of the RV let me know. If there is some sort of industrial chart concerning these issues that would also be great.”

Great question Bill and welcome to the world of RV ownership. I know you would like an answer like “the Max temperature is 149.6°F and pressure increase of 12.8 psi” but as you are learning with tires nothing is that simple.

First off I strongly support having a TPMS. Even if you check your pressure with a good digital gauge every morning, how will you know if you drive over a nail as you pull out of the campground at the start of your day’s travels?

Next you need to get your real individual tire loads with the RV fully loaded to be sure you are not overloading any individual tire. You have a Tire Placard that indicates the recommended cold tire inflation you should follow until you know your real loads and calculate your personal minimum inflation levels.

 As you work through my earlier posts you will see the general guideline for pressure increase of about 2 percent for every 10°F, so if you set your cold pressure to 80 psi in Oklahoma City in November and it's 45°F you may see your cold pressure has increased to 86 psi in Phoenix the next morning when it is 85°F. If you watched your tire pressure during your trip you might see the tires run from five psi to 20 psi above your cold pressure as the tire temperature warmed up to 20° to 50°F above ambient. This increase in tire temperature is affected by many variables such as load, speed, air movement around the tires (inner duals will usually run hotter) and moisture content of the inflation air and actual tire inflation. Also if it starts to rain you will see a very quick drop in tire temperature and an attendant drop in pressure as the water draws away the heat being generated in the tire.

Be sure to check out “Quick post on Max tire temperatures” and Tire Temperature & Pressure - A Hot Topic and Are tire pressure monitoring systems “TPMS” worthwhile?

Why should I weigh my Trailer tires individually?

Many times when I give a seminar or class to people from the RV community on proper application of tires, I get asked the above question by trailer owners.


Motorhome users seem to understand that knowing the actual load on each corner of their RV will allow them to select the tire pressure they want to run as they balance Ride, Tire Durability, Fuel Economy and Steering Response.
Owners of trailers say they have been told that all they need to do is to run the max inflation on the sidewall of their tires. Almost all the time, that is the information on their placard per the trailer manufacturer’s guideline so that recommendation seems reasonable.

Recently I have been having a discussion via email with an owner of a large 5th wheel trailer.
He even believes that because the load changes on every trip and almost every day it could be “dangerous” to get the trailer weighed as that could mislead the trailer owner to think it OK to lower the pressure to just match the minimum needed to carry the measured load. I would like to offer a different view on why it is important to get the trailer weights on each tire at least once.

More than half of the trailers that have been weighed over the years have been found to have a tire or other suspension component exceeding its maximum load capacity. We all know what happens to people who “Assume” something. When you get the trailer weighed, it does need to be with all the stuff you normally carry on your travels. Knowing this load you will have the facts to see how critical it is to re-distribute the load side to side or front to rear. You will also know if your unbalance has overloaded one or more tires even when the total load seems OK. You will also know if you have proper loading on your pin. I have heard that some axle manufacturers consider having one end of an axle loaded to more than 50% of the total axle rating as overloading the axle. This means that even if you have changed wheels & tires to not overload those components you might still be overloading the axle if you are not careful.

Another thing to consider is the “Reserve Load”. That is the “safety factor” between the actual load and the calculated maximum for a component. Most cars have a 12 to 18% reserve load. One of the other benefits of having a good sized Reserve Load is that it will allow you to occasionally bring home that big load of stuff you just had to buy at the flea market and not overload a component. One way to identify a minimum cushion would be to look at the load capacity of your tires when inflated to a pressure of at least 15 psi below the max inflation and to be sure your load does not exceed that level. A 20 psi cushion would be even better. Reserve load helps compensate for the unbalance that occurs due to side loading because of road crown and wind side loading.

You are probably asking yourself why trailers can’t lower their tire pressure the way motorized units can. The reason has to do with the mechanics of axle spacing and tire side loading whenever you turn a corner. Trailers with two or three axles put enormous side loading on the tires, wheels, and axles whenever they turn corners. A quick look at the tire distortion when you see a big twin axle trailer park will confirm that the tire needs to be as stiff as possible when side loaded. Since we all know it is the air that carries the load we also now realize that it is the air that stiffens the tire and as a result will lower the side deflection and loading.

BOTTOM LINE: Next time you are fully loaded please go to the effort of weighing your trailer and go the extra mile to do the multiple weighing and the math needed to calculate the actual load on the individual tires. Remember a blown trailer tire can lead to substantial damage and financial loss.

Certification Label otherwise known as a “Placard”

Along with others who deal with tire questions, I too often incorrectly assume that the information on all placards is complete, correct and consistent and that the owner knows where to find this sticker. This incorrect assumption comes from looking primarily at car placards from vehicle manufacturers that have regulatory compliance engineers working for them.

However, when it comes to the information on these labels for RVs, there have been significant changes in both the information that is included and the location for the placement of the sticker and it seems that not all RV manufacturers pay as much attention to the accuracy of the information on the placard as others.

Do you know where your placard is located?
Are you sure the information is both complete and correct?

Over the past few years both the location of the sticker and the information requirements have been changed.

Newer Cars and Pick-ups will have a color sticker with this information.

This sticker will be located on the driver’s door jam




When it comes to full size RVs you may find the placard in a closet










Some Class-A units will have the stickers near the driver’s left arm location

Note the lack of complete tire size on this older sticker with only the rim size identified.

Newer Class A should have a placard at the driver's location.

But may have more complete information in another location like a closet.


This newer Super-C seems to have all the information the owner needs.




Some owners will be lucky and have actual unloaded weights.




Finally here is an example of a placard applied by a manufacturer that didn’t follow the requirements. Clearly the trailer does not have two 12,000 Lb axles running dual tires and the tire cannot carry 6,000 Lbs each. There might have been a recall if the trailer manufacturer was still in business.


The bottom line is:
1. Find and know the location for the placard for all your vehicles.
2. Make a note of the minimum inflation as recommended by the vehicle manufacturer and add this information to your travel check-off notebook
3. Confirm you have the same size and Load Range tires as identified on your placard.
4. If you find a difference or have a question snap a picture of your placard and send me an email with your questions –tireman9@gmail.com- and I will try and help sort out the questions you might have.