If I upsize my tires can I lower my inflation?

 I Got this question.

Hi Roger. I have a tire question for you. I own a 2021 RV with a GVWR of 8596 lbs, that I purchased used in the spring of 2024. The factory 205/75R15 GY Endurance tires were manufactured in November 2019 and I believe they are due to be replaced. I am considering replacing them with GY Endurance 225/75R15 for the increased load range to give myself a wider margin of safety as the 205’s load range is basically equal with the GVWR for the camper. My question is this:
My 205’s are rated for 2150 lbs at 65 psi, which is what I’ve been running them at. According to the Load/Infl chart, I could theoretically run the 225’s at 50 psi for the same 2150 load. Obviously, I want more load capability so I would run them at a higher psi, say 55 or 60. But is it safe to run the at a lower psi since they are rated to 2830 lbs at 80 psi? I don’t need that much load capability and would prefer the softer ride of a lower pressure as long as it’s safe to do so and not be overheating the tires.
Please let me know what you think with regards to running this particular tire at less than max psi.

My Reply

Hi

 I work as the "in-house Tire Expert" for RV Travel.com, so your question landed on my desk.

First, it's essential to understand what the "GVWR of 8596 lbs" means. That rating is the heaviest your RV should ever be. In fact, RVIA recommends that the tire loading should be no more than 90% of that number. Additionally, certain assumptions are made when arriving at that number, namely that the load on your tires is evenly split between the axles and that the load on each tire on an axle is evenly distributed from end to end.

RVSEF has measured the actual load on tires on tens of thousands of RVs and learned that over half of tires in RV usage are being overloaded. This data supports the recommendation that, at a minimum, every RV should get on a Truck Scale and at least learn the weight on each axle. Getting "4-Corner Weights" is not always convenient (see RVSEF) so I suggest we assume one end is supporting 53% of the axle total. Going to this effort is important as the inflation in the tables is the MINIMUM inflation for the heaviest loaded individual tire, and all tires on the trailer should have the same cold inflation.

You mention "Safety" a few times. Tire inflation safety is not an on/off switch where tires will quickly fail if you drop 1 pis below the table number and run for 10 years if you are a few psi above the minimum.

 

If you review my posts on my blog RVTireSafety.net, or if you do a search on "Tire Inflation" on RVTravel.com Maintenance tab you can find many posts on the topic.

 

The short answer to your question on new tires:

Yes, you can go up in load capacity IF you also go up in inflation and up in Load Range

I recommend you confirm the load on each axle (when the RV is fully loaded to the heaviest you ever expect to be (full water, food, tools, clothes etc) by getting on a truck scale.

Use the heavier scale number and apply the suggested 53% figure to arrive at your tire loading number.

Consult the Load & Inflation tables for your size and Load Range tire to learn the MINIMUM cold inflation that you would use for all your tires.

On my RV, I use the above and then add 5 psi to that number and make sure my inflation never drops below the Minimum by reading my TPMS display.

How and why to photograph your tire sidewall info

I recently received this comment/message/question about tire sidewall info:

A material list on the tire sidewall? I’ve never seen this. It sounds like FDA package list of: flour, corn syrup. Reading black bumps on black might work in ideal lighting, but I have trouble finding the max PSI.

I replied with this:

The list of materials and the max load numbers are easily seen molded on the sidewall of all tires per Federal Regulation for the last 30 years. The US-DOT specified  size, location and content are as seen in the attached examples. These pictures were taken with natural lighting and not even in direct sunlight.

To read letters molded on your tire sidewall, you might find it easier if you get out your phone aka camera and snap a couple of pictures of this important information.

I suggest you wash your tire sidewall with soap and water and snap pictures of three areas with the tire in full sunlight. Here are examples from three different tires:

 1. The complete DOT serial

NOTE: You should confirm all your tires have the same serial number. If not, get a picture of each serial number.

 

 

 2. The tire max load information

 

 3. The tire material list

Note on “Max psi”: You should focus on the “Max Load” and understand that the tire is only rated for that load when the tire is inflated to the stated PSI, and the inflation is checked at ambient temperature. The “Max psi” IS NOT the highest level of inflation a tire can tolerate. Undamaged tires can tolerate much higher PSI when warm from running.

Keep in mind, if you have the tire sidewall info handy in a photo or on your phone, it will be much easier for you than if you have tire problems in the middle of the night and don’t know what tire you need for a replacement.