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Friday, February 15, 2019

Small Single axle travel trailer tire inflation

I have received questions on tire inflation from folks with small single axle travel trailers, boat trailers, and utility trailers. There is some confusion, which I understand, so let's see if I can clarify my recommendations for inflations.

One common bit of information would be to learn the actual load on each tire position when the vehicle is loaded to the heaviest you ever expect it to be.
- For each axle identify the heaviest end and use that load when consulting tire load & Inflation tables.

Motorhomes  and Trucks
These vehicles would use the heaviest axle end load when consulting the Load & Inflation tables.

- The inflation needed to carry or exceed the measured load would be your MINIMUM inflation.
- I suggest you select inflation that will provide at least 15% "Reserve Load" for your Cold Inflation Pressure. Some find it easier to go with a +10% inflation over the inflation in the tables.
- Just be sure you have some Reserve Load capacity.
- I see no problem with running higher inflation as shown on the "Vehicle Certification Lable"

Trailers with a single axle
- There can follow the same guidelines as seen for Motorhomes.

Trailers with two or three axles
- Run the inflation molded on the tire sidewall that is associated with the tire "Maximum Load" capacity. many RVs show that inflation on their label, but it is still a good idea to ensure you have a reserve load capacity. SOme RV companies provide almost no load margin so it is up to you to make the appropriate adjustments. Running the tire sidewall inflation will give a lower Interply Shear force which, as you know, is a primary cause of belt separations on these RVs and are why tire life is about half what it is of comparable tires and loads on Motorhomes.
- Select the heaviest load as measured on all four or six tire positions and confirm that the tire load capacity at the sidewall inflation provided at least a 15% Reserve load.

For those interested in the science behind Interply Shear you might read this post.


  1. I have a teardrop trailer GVWR 2900 lb and am considering a tow vehicle with a compact spare (Honda Ridgeline, towing capacity 5,000 lbs). Do you think it would be safe to tow with it’s compact spare in the event of a flat tire just far enough to get it fixed?

  2. We are RV newbies and recently purchased a used 2020 Gulf Stream Vista Cruiser travel trailer. It has 2 axles. I've been reading through your posts, and I understand that the load is inherently unbalanced, especially where there is a slide. We have a slide on our driver's side. On our first venture out with the trailer, we had a blow out of the rear tire on the driver's side after a few hundred miles (thanks to a passerby, our damage was limited to the tire, thank goodness). We now know that we should have checked tire pressure before departing - rookie mistake. We have purchased TPMS for all 4 tires and will use that in the future in addition to checking our cold pressures before we head out. We're currently arguing over whether to purchase new tires (me) or replace only the blown one (the spouse) - a whole other conversation. Here's my confusion. I have seen your posts about adding 10% to cold inflation, and other information indicating the manufacturers add in that margin of error to the recommended psi? We currently run on ST205/75R14D (build code 2518 if it matters). The sidewall says "Max Pressure 75 psi Cold". The sticker on the side of the trailer says "Cold Tire Pressure 75 psi). Does that mean we should ensure we are at 75 psi in the morning, or should we inflate to 10% over that amount - i.e. approx 82 or 83 psi? And would this inflation apply regardless of load on each tire? I know we need to get each tire position weighed (I assume we need to go to a CAT scale for this?) to determine load, but I want to be as safe as possible until we can get to a scale.


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