What's the right tire pressure?

In the RV world there's always a lot of chatter about tires. It might seem strange that tires are such a big topic, since most of us barely think about the tires on our car or truck unless they need to be replaced.

For travel trailers in particular, tires are a big deal for several reasons:

  1. You can't feel anything if a tire goes flat while you're towing (which is precisely why a TPMS is essential).
  2. Trailer tires take a lot of stress in turns, and from things like hitting curbs.
  3. Trailer tires tend not to get used as much as car tires, so they often "age out" just while sitting in storage.
  4. A tire failure on an Airstream trailer can cause an incredible amount of collateral damage to the aluminum body, which is very expensive to repair.

One of the biggest questions is simply, What's the right tire pressure?

If you have an Atlas or Interstate motorhome, the recommended pressure is easy to determine. Look the "Tire and Loading Information" placard located (typically) on the driver's door jamb, or check the Mercedes-Benz Sprinter Owners Manual that came with your motorhome or details. Keep in mind that there might be different pressure recommendations for front and rear wheels.

For a travel trailer, it can also be very simple—or not. The Federal Certification Label attached to the outside left of your Airstream tells you everything: the size of tires the trailer requires, the maximum load the trailer can carry, and the recommended tire pressure.

For a late model trailer, it's going to probably say 80 psi for the tire pressure, which is the maximum pressure the tires should have when "cold" (meaning before you start driving).

There's absolutely nothing wrong with using 80 psi for the Goodyear Endurance tires. I do, and so do the majority of our customers. But sometimes people look at Goodyear's "Load/Inflation Information" table, which is published online, and see that they could run lower pressure based on the weight of their trailer. Then, somebody online claims that lower pressure is "better for the Airstream," or that it gives a "softer ride"—and suddenly the choice of air pressure gets a lot more complicated.

First off, let me dispel the myth that lower air pressure is better for the Airstream. Your Airstream is extremely tough and doesn't need "soft tires" to survive.

Sometimes people point at a broken pop rivet on the interior as evidence that the tire pressure should be lower, but that's just a supposition. Pop rivets sometimes break and it doesn't necessarily mean anything (and you can easily replace them yourself with a simple tool, as we've demonstrated in this video). If your Airstream is losing a lot of rivets, or the bucked rivets on the outside are breaking you may have a structural problem that needs investigation, but the root cause isn't the tire pressure.

If you want to go the route of choosing a lower air pressure, you'll have to do some homework. The first step is to know how much the trailer weighs including all the stuff you've packed.

I talk about the process of weighing a trailer briefly in The Newbies Guide to Airstreaming, and in much more detail in The (Nearly) Complete Guide to Airstream Maintenance. If you don't have a truck scale nearby, you can estimate the typical loaded weight of the trailer by adding:

  1. "Factory Manufactured Weight" from the Federal Certification Label
  2. Estimated weight of your belongings (clothes, gear, food, tools, etc)
  3. Weight of water in the Airstream (the number of gallons in the holding tanks and the water heater @ 8.3 lbs/gallon)
  4. Net weight of two full propane tanks (typically about 60 pounds) 

Compare that total weight to the Goodyear Endurance Load/Inflation table and see what pressure you could run if you wanted. (Keep in mind this example applies only to Goodyear Endurance tires. If you have another brand, don't use this table.)

For example, let's say your full load was about 6,300 pounds on a trailer with four wheels, and your tires are the Endurance ST225/75R15 model. That's 1,575 pounds of weight per tire. 

According to Goodyear's table, you could set your tire pressure as low as 30 psi. But should you? Unless you're experiencing some significant issue, like the tires are wearing in the center, you don't have to lower the pressure. You can continue to use a higher pressure.

I generally recommend customers stay with the maximum tire pressure for one key reason: if you ever have a leak from a nail or screw, you'll have a lot of buffer before the tire goes critical and starts to shred itself. That gives time for you or your Tire Pressure Monitoring System to detect the problem, which could save you from an expensive repair.

 

Photo by Jahongir ismoilov on Unsplash

10 comments

Gerry

Gerry

Hi, I have Michelin light truck tires which state 50 PSI. Not sure I sure put 80 PSI.
Your comments please.
Thanks,
Gerry

Edward Johnson

Edward Johnson

Well written. We keep our Goodyear Endurance tires at about 75 PSI for our 19’ International. Every so often we pull through a truck scale while fully loaded and check the weight on the axle and tires. Continues to be at about 3800# and with the trailer rated at 4500#, we are at 85%.

William E Yanke

William E Yanke

Do you add or subtract air depending on the cold temperature at the start of the day and the elevation you are driving at. Temperatures of 110 degree F like we saw last summer in UT led me to bleed a little air out but only at the start of the day when the tires were cold (it was still 80 degrees outside) and prior to driving.

Brian Kirk

Brian Kirk

Great Article. One minor correction on the weight of water. Water is 8 lbs per gallon (8.345 more precisely).

Claudio Martin

Claudio Martin

I have Michelin Defender LTX M/S on my Caravel 16RB. Maximum pressure on sidewall is 50psi (and load 2315 pounds) so I think you need to consider that in making a recommendation. I run them at 45psi.

Dave

Dave

Another reason to use the higher pressure is that the assumption that total weight divided by number of tires is a good metric – unless your weight is perfectly distributed, this is a bad assumption. The example asserts 1575 lbs per tire. But your load could actually be 1800 lbs per tire on one side of the trailer and 1350 per tire on the other. If this is the case, you are going to have underinflated tires on one side and will eventually see uneven wear and/or failure. Better, I think, to go with the recommended inflation for most cases.

Greg Heffington

Greg Heffington

“One key reason” is enough for me. Have been running max pressure from the get go and have had blowouts as well. The buffer is helpful as is the TPMS.

Craig

Craig

A nice article. I also use 80 psi unless we have an extremely hot day. Then I may start at 77psi cold. A former tire engineer, Roger Marble, who has a forum on an RV travel website strongly suggests using the recommended maximum cold inflation to reduce sidewall stress on trailer tires particularly during turns and backing up. I also use a TPMS.

Rich Luhr

Rich Luhr

Gerry and Claudio: I was using 80 psi as an example only, because the Goodyear Endurance ST225/75R15 tire is the most common one used on new Airstream trailers and it takes 80 psi. You shouldn’t put in more pressure than the “MAX COLD PSI” stated on the tire sidewall.

William Y: As you move around the country, the air temp and altitude may change. So yes, you should adjust air pressure in the morning when the tires are “cold” if needed. Most often you’ll need to add air, not remove it.

Brian and others who wrote about my typo: Yes, water weighs a little over 8 lbs per gallon. I originally wrote “6” but that was just an error. (I was thinking about gasoline weight!)

Rich

Rich

👍 great article Rich.

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