Selecting the Ideal Tire Pressure for Multi-Axle Trailers
Determining the correct tire pressure for your travel trailer can be a challenging task. To provide you with accurate information, we consulted with Roger Marble, a highly experienced tire engineer with 40 years of expertise. Based on our discussions, Fifth Wheel Street now offers new guidance.
Maximum Load PSI Rating and Tire Pressure Adjustment
We no longer advise adjusting the inflation pressure of trailer tires below the pressure associated with the maximum load PSI rating indicated on the sidewall. This advice applies to tires with a maximum rating of 85 PSI or lower, as long as the wheel or rim is also appropriately rated. For trailers with tires rated higher than 85 PSI, you can refer to the manufacturer’s tire load charts and add a 25% margin.
Until your trailer has been weighed, never inflate the tires below the manufacturer’s label or the maximum cold air pressure molded on the tire if the max cold air pressure is greater than 85 PSI.
Weighing Your Trailer for Optimal Load Distribution
To ensure your trailer’s axles and tires are not overloaded, we highly recommend weighing each tire position on both the trailer and the tow vehicle or motorcoach. Unequal weight distribution is a common issue, particularly for Toy Haulers. Incorrectly distributing the load can cause overloading and potentially exceed the maximum weight capacity of a tire or axle. It’s worth noting that reports suggest many RVs are traveling with at least one overloaded tire or axle side.
Unfortunately, obtaining accurate individual tire position weights is usually impossible at truck scales. To help you, please refer to a list of recommended RV Weigh-masters listed on our website.
“Interply Shear on tires in trailer application needs to be considered as this is a major contributor to trailer tire belt separations.” – Roger Marble
Our Tire Pressure Recommendations for Multi-Axle Trailers
Regardless of the measured scaled weight of each tire or axle position, we recommend inflating the tires to a pressure no lower than the PSI associated with a maximum load of 85 PSI or less. You have two options for determining the appropriate tire pressure:
Option One: Consult the minimum tire requirement stated on your vehicle’s Certification Label. Please note that this value represents the maximum cold PSI for the original equipment manufacturer (OEM) tire. If your trailer currently has different tires than those mentioned on the OEM label, please proceed to option two.
Option Two: Inflate the tires to a pressure no lower than the tire’s cold PSI value indicated on the sidewall, considering the max load. Ensure that you do not exceed the wheel or rim PSI rating for tires with a maximum pressure of 85 PSI or less.
To better understand the importance of maintaining the correct tire pressure, take a look at the diagram below. It shows how the tires on one axle bend inboard while the other is forced outward.
- Never exceed the maximum load rating stated on the tire’s sidewall.
- Most Special Trailer (ST) tires have a maximum rated speed of 65 MPH. We recommend towing at a maximum speed of 60 MPH with most ST tires (although some companies offer ST tires with higher speed ratings).
- Do not exceed the maximum inflation rating for the wheels, rims, or valves when setting the tire cold inflation pressure.
- Avoid inflating tires more than 10 PSI above the maximum PSI rating imprinted on the sidewall.
- Always use tires that meet or exceed the requirements specified on the Certification Label.
- Do not consider anticipated temperature changes during the day’s travel when setting the morning cold inflation pressure.
- Note that inflating tire pressure above the tire’s sidewall rating does not increase the load rating.
Please note that RV expert Mark Polk has written an excellent article about using LT tires on trailers, which you can read here.
RV Tire Load Inflation Charts
In the absence of a brand-specific chart, you can refer to any chart below that lists the same tire size as the ones installed on your trailer.
Images courtesy of Fifth Wheel Street