Handling the [tire] Pressure

Tire pressure is different for each RV, even those of the same make and model. It is determined by a tire's construction and ability to support weight. Weighing your RV is the only way to know the weight carried. These weights are then compared to the tire manufacturers weight and tire air pressure chart to identify the correct pressure for each of your tires.

Unfortunately many RVers are unaware of this critical information or go about the process incorrectly, leading to the potential for catastrophic tire failure, damage and injury.

“Handling the (tire) Pressure” explains the issues and misconceptions, walks you through the correct process of determining the correct tire pressure for your RV and shows you how to set and maintain the pressure.

NOTE: The following information is provided to raise your awareness of the need for proper tire pressure settings and maintenance. It is not intended to supplant the recommendations and requirement specified by your tire or RV manufacturer. Always follow the instructions they provide.

Pressure is Critical

Riding on over or under-inflated tires affects fuel consumption, tire wear, braking distance and traction and ultimately the safety of those in your RV as well as others sharing the road. Improper inflation is the number one cause of catastrophic tire failures such as blowouts.

The weight a tire bears and its air pressure determine the shape of the tire and the amount of tread on the road. An overinflated tire will round on the bottom decreasing the amount of tread in contact with the road surface resulting in premature tread wear and poor traction and ride comfort. An under-inflated tire causes the outer edges of the tread to wear prematurely and also reduces the amount of traction available from that tire. An under-inflated tire will also heat up more and this heat can lead to sudden tire failure such as a blowout.

Correct air pressure is determined by the construction of the tire and its ability to bear weight. All tire manufacturers publish charts indicating the correct pressure settings for varied weights for each tire model, size and load rating. These values specify the correct tire pressure when the tire is measured cold — at the ambient air pressure. As a tire rolls, it builds heat and is no longer “cold” or at the ambient temperature, thus producing false pressure reading.

Misleading Indicators

One of the tire pressure challenges RV operators face is the confusing and potentially misleading information they are provided with regarding their tires. Tire inflation pressures are stated on the sidewall of each tire and otire codes

n a tire information placard inside the RV. Unfortunately, this information is often misunderstood, resulting in improper tire pressure settings.

The following illustration indicates a tire pressure of 50 psi. Unfortunately, most people overlook the preface to this pressure indicating that 50 psi is the “maximum” pressure when the tire is carrying a 3,000 lb. load. Your tires may not be carrying their maximum load capacity and therefore the indicated “maximum” pressure would cause an overinflated condition.

The tire and loading information placard, provided by the RV’s manufacturers indicates the correct tire size for each axle of the RV. It also specifies a tire pressure setting for each tire when carrying a specified weight — the curb or unloaded weight of your RV when delivered new. Though your tire pressure should never be lower than the indicated amount, in every likelihood your RV will be loaded with additional weight and therefore require a higher air pressure in your tire.

The weight ratings for your RV are posted on the recreational vehicle chassis, or within the recreational vehicle itself. Depending upon your RV type, some of the information may vary.

  • The GVWR (Gross Vehicle Weight Rating) is the maximum total weight rating for the recreational vehicle, including passengers, fluids, and cargo.

  • The GAWR (Gross Axle Weight Rating) is the maximum weight allowed across a single axle.

  • The UVW (Unloaded Vehicle Weight) is the weight of the recreational vehicle as built at the factory with full fuel, engine oil, and coolants. The UVW does not include cargo, freshwater, LP gas, passengers or dealer-installed accessories.

  • The GCWR (Gross Combination Weight Rating) is the maximum allowable loaded weight with a towed trailer or towed vehicle.

These ratings can vary based on the different components, configurations and vehicle options. To determine proper inflation pressure for your tire, you must weigh each wheel position with the RV fully loaded, as it will be used.

Weighing wheel position will give a clear indication of how the weight of the recreational vehicle is distributed on and across each axle. If there is a significant weight difference front to back or from one side to the other, you can adjust your cargo to improve the weight distribution for improved handling and ride comfort.

Do not simply go by the tire pressure set when you received your RV or by what the salesman said.

Initial tire pressure settings are invariably incorrect and most RV salespeople are ill-informed in this area.

Weighing the Situation

To adjust your RV's tire to the correct pressure you must:

  1. Perform a “4-corner weigh” of your RV.

  2. Lookup the correct pressure for each tire and the weight it is carrying, based on the tire manufacturer’s pressure chart.

  3. Check, and if required, adjust the air pressure in each tire.

Performing a 4-Corner Weight

NOTE: The following example demonstrates the weighing process for a motorhome but the process for other motorized and non-motorized RVs is the same, you just have to adjust for the number and location of your axles.

Prepping Your RV

Prepare your RV for weighing by loading it to its normal "full" travel weight. Your freshwater, propane and fuel tanks should all be full and your black and grey holding tanks empty. When you weigh the RV, you'll also need the driver and all passengers in their normal travel locations. If the above is not done, your weight distribution will be incorrect and your work for naught.

"Platform" scales are usually long and designed to weight an entire vehicle, all at once. You'll have to position your RV so that only one axle is being weighed at a time.

"Segmented Platform" scales provide two or more individual scale sections allowing multiple axles to be weighed at once, but with only one axle on a scale section at a time.

"Single Axle" scales are the most straightforward as they accommodate only a single axle at a time.

“Portable” scales are able to moved from one location to another and require minimal space. They weigh one tire at a time but you’ll often see two or four being used together.

Regardless of the type of scale, the goal is to get individual weights for each axle.

Unsuitable Scales

Some scales are unsuitable for properly weighing an RV as you are designed only for weighing a complete axle with obstacles preventing a single-side from being weighed.

Find a Scale

Okay, our rig should be weighed and the CAT scales I see at many truck stops don't work for a proper 4-corner weigh — so where do I find a scale?

There is no simple, one answer fits all, so you may have to do some research. Here are some examples of places I have found and used:

  • RV rallies: RV weigh services are often available at large RV rallies. Look around and ask questions early in the rally as they typically set up appointments and some that I have been to fill up their schedule fast.

  • Repair shops: I have seen and had my RV weighed at repair shops that have their own portable scales. These are usually shops that work on RVs and do alignment or other suspension work.

  • Commercial truck scales: Though many are not suitable for 4-corner weigh procedures, many are as well. Keep an eye open for scales at truck stops while travelling and note if there is sufficient access.

  • Government scales: Government and DOT truck scales are often left operational when the scale is closed. If the scale readout is operational, you do your own 4-corner weigh free of charge.

Weighing Process

Many people mistakenly think that all you need are total axle weights. From a strictly legal perspective, that is all that is required to ensure your axle weights are within their legal limits. However, this simplistic approach does not identify side-to-side imbalance.

Weigh Procedure Steps:

  1. Position the complete front axle over the scale and record the weight.

  2. Position the complete rear axle over the scale and record the weight.

  3. Position the left wheels only of the front axle over the scale and record the weight.

  4. Position the left wheels only of the rear axle over the scale and record the weight.

Add weight steps for any additional axles using the same "total axle" and "left side only" format.

With a little simple math you can use these weights to determine your right-side weight. Total axle weight, minus left-side weight, equals right-side weight.

Below is an example of an RV Weight Worksheet I created in Google Sheets, an Excel-like spreadsheet. You may wish to create one similar that reflects the axle configuration of your RV.

The above example shows my tag axle motorhome with both the total weight for each axle plus the individual left and right side weights.

By including the GAWR (Gross Axle Weight Rating) I can also verify that each axle is below its maximum limit. In this case, my drive and tag axles are well below their limits but my front axle is a mere 400 lb. below its limit.

By rearranging cargo in your basement and cabinets, especially heavy items, you can effectively shift your weight front to back and side to side. Ideally, you want the load as even as possible.

NOTE: Having this information in a spreadsheet enables easy calculation of the weight numbers and track air pressure changes.

Load/Inflation Specifications

Each tire manufacturer publishes the tire inflation specifications for each model and size of the tires they produce. Google “X tire inflation specification”, with X being your tire’s manufacturer, to find the chart for your tires.

NOTE: The correct air pressure varies for each tire model, size and load rating. Referencing the correct tire is crucial.

In my case, I have Michelin X Coach 295/80R 22.5 tires on my steer (front) and tag axles and dual Michelin XZA2 295/80R 22.5 tires on my drive axle.

Commonly, one side of a vehicle will be heavier than the other. To prevent dangerous under-inflation, use the heaviest weight on each axle. For me, this means:

  • Steer axle - 7,250

  • Drive axle - 7,700

  • Tag axle - 3,750

Identify the closest weight, greater than your actual weight, for each axle.

  • Steer axle - 7,250 > 7240 on chart

  • Drive axle - 7,700 > 9350 on chart (duals)

  • Tag axle - 3,750 > 5575 on chart

Note that the steer and tag axles weights are far below the lowest value on the chart, so the lowest number is used. Also, note that there are different values for the same tire when used as a single versus dual tire installation.

The correct air pressure for each tire is noted along the top of the chart:

  • Steer axle - 7,250 > 7240 on chart > 105 psi

  • Drive axle - 7,700 > 9350 on chart (duals) > 75 psi

  • Tag axle - 3,750 > 5575 on chart > 75 psi

Some professionals suggest adding 5 psi to any tires on an axle that may be subjected to occasional heavier loads.

Tire Care & Maintenance

Each tire must be checked frequently for both pressure and roadworthiness. Uneven tread wear, curb scuffs, cuts and cracks (checking) can be just as dangerous as improper inflation.

All tires should be visually inspected before travel and the air pressure checked at least once per week. For long trips, do a complete inspection and pressure check each day, before pulling out of your campsite.

Check tire pressure only when the tire is cold (ambient temperature). As you drive, tire temperatures will increase, as will the air pressure in the tire. A “hot” tire may indicate a pressure increase of as much as 10 – 15 psi over its cold reading.

NOTE: Do not bleed pressure from hot tires as this will result in dangerous under-inflation. The cold inflation specification considers this pressure increase.

Tire Pressure Monitoring Systems

Several brands of Tire Pressure Monitoring Systems (TPMS) are available for recreational vehicles. They come in two formats; ones with external sensors mounted on the tire valve stem and internal units, incorporated with the valve stem.

When properly used, a TPMS can improve safety and tire performance but often they are misused as a means of verifying tire pressure, supplanting proper tire inspection.


Nitrogen is a dry inert gas that does not retain moisture and is more tolerant to temperature change. These attributes are advantageous for an aircraft flying in sub-zero temperatures or a race car driving at blistering speed but the benefits of nitrogen are generally not applicable to standard over-the-road vehicles, such as recreational vehicles.

Service Life

The serviceable life of most RV tires is determined by road damage and/or age rather than tread wear.

Tires are more complex than they appear. They are designed for a variety of usage scenarios and contain up to 200 different raw materials. Over time, these components may degrade or become stressed due to physical or environmental forces, possibly intensified by improper inflation, exposure to UV light and more. Some tire manufacturers suggest the tires should be replaced after 6-years while others suggest a service life of 10-years from their date of manufacture. Most tire manufacturers suggest that tires greater than 5-year of age, based upon their manufacture date, should be inspected by a qualified tire specialist.

Regular inspections and proper inflation will help you get the maximum life from your tires.

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