RV Tire Safety: Air compressor – How big do you need?

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with RV tire expert Roger Marble

While air volume output might be a consideration, IMO if you are properly inflating your tires and properly monitoring inflation with a TPMS, I don’t understand how anyone can get in a position of needing more than about 5 psi unless you have an active leak.

As I have covered a number of times in this blog, I recommend your cold inflation pressure to be at least 10% above the minimum needed to support your actual measured tire loading. (Minimum inflation would be based on the heaviest loaded tire on any axle or, lacking individual tire loading numbers, then using an assumed 53/47% side-to-side split for motorhomes and trailers with big slides or residential refrigerators, and at least 51/49% load split for smaller trailers.)

So assuming you have LR-C or LR-D tires you would be inflating to 50 or 65 psi with your TPMS warning set to no lower than 49 or 64 with your minimum inflation in the load tables being 45 and 58. So how would you ever need to add more than 5 or 6 psi assuming you let your tires get that low? Why not do your “top-off” as soon as you need 3 psi? Now you do need to consider the 1 or 2 psi difference between your calibrated hand gauge and the TPMS reading. I set the warning based on the TPMS reading AFTER setting the tire using my certified hand gauge.

Yes, pressure changes with temperature (about 2% for change of 10° F temperature). A change in morning temperature of 40° F from day to day is unusual and that would only result in a pressure drop of 5 psi on your LR-D tires.

Motorhomes should be running a +10% margin on air pressure based on the measured tire loading, which means there would need to be a 50° F drop in temperature for them to need to add 10 psi (assuming a 100 psi minimum).

If you need to add more than 20% (20 psi) of the needed pressure in your tires with steel body ply, that means you have technically been operating on a “flat” tire, according to tire industry standards, and you should have a professional inspection and have them reinflate your tires AFTER the reason for the sir loss was identified and repaired. Large 19.5 and 22.5 tires should only be reinflated in a cage (watch the video) just in case there was damage to the steel body cords which can lead to an explosion (watch the video) due to zipper rupture.

LR-E (80 psi polyester body tires), as found on most Class C and some larger trailers, need to consider the above information and adjust for their higher cold inflation numbers. I would consider a 20% drop to put you in the safety cage reinflation level if you drove on the tires when that low. While they are not likely to suffer a true “zipper” failure from fatigued steel body cords, there can still be internal structural damage to your tires.

Bottom Line:  Monitor your tire pressure and don’t let the pressure drop more than 10% before you reinflate your tires. Know why the pressure dropped and if not due to a drastic change in temperature overnight, inspect for leaks. I find that spray cleaner like Windex or other cleaners tend to foam at the location of the leak.

 

Read more from Roger Marble on his blog at RVtiresafety.net or on RVtravel.com.

 ##RVT934

 

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H. Ramsay

From the article title, thought I would learn info on different sizes and output of compressors. All the acronyms are confusing. So are all the different types of compressors. Also prices that range from $50 to $250. This article didn’t help me with any information on the different sizes and air outputs. 🤔

Gary

I carry a small 12V tire pump just in case I need to do some serious inflating. I also carry a decent bicycle pump for the bikes. In the morning if I need to bring the RV tire pressure up 2-3 psi, or even 5 psi, I find the bike pump does the job just fine. I get some exercise and don’t have to deal with dragging the 12V pump out, running the cable, disturbing my neighbors…

Mark B

5 PSI air compressor article is flat. Felt like the article started in mid-sentence and ended in mid-sentence. A link to a succinct primer would have helped those of us who don’t know an LR-E from a TR416S valve stem.

Ed Stieren

Have you have in info on camper wheel failure? 2014 Jayco bought new.3 of the 5 wheels developed slow leaks starting late 2018.That a 60% fail rate.

Wolfe

Is your “unsafe flat” threshhold affected by whether the tire is rolled? This being winter, any slow leak is far more likely to go unnoticed during storage, but the tire isn’t rolling on the flat (flexing the sidewall a few hundred-thousand times before discovery). For example, if an LR:D 65psi tire gets down to 30psi but is topped off in place before rolling, is that still an unsafe tire having been “pooched” even ONCE?

BTW: I keep my TPMS “active” all winter — the solar receiver goes in shop or my truck (driven all winter), so I still get periodic updates and notice a developing problem.

Bill

The article opens by saying –
” …if you are properly inflating your tires and properly monitoring inflation with a TPMS, I don’t understand how anyone can get in a position of needing more than about 5 psi unless you have an active leak.”

At first read, this might be a little misleading to a newcomer, since a compressor that puts out only 5 psi won’t do anyone any good. I believe what is meant is “…5 psi [u][b]above the intended final tire pressure[/b][/u].” In other words, if you intend to inflate a tire to 65 psi, your compressor must be capable of at least 70 psi.

Jeff

As Roger says, significant leaks should be used with a Soapy water mix and the big thing too, check around the VALVE STEMS too. I had a recent tire that went flat on my truck, changed out the spare and took it to a local tire shop. They inspected the tire and couldn’t find anything wrong with it. No nails or foreign objects in the tread. Then the tire guy sprayed some soapy water around the Valve stem and there it was. Leaky Valve Stem. Replaced it quickly and tire is like new again!

Jeff

Reminds me of the time in the USAF, working on B52 Tires in our maintenance Shop! We had a Special CAGE for these HUGE TIRES. I’m guessing it was made from 6 inch or more Pipe, like in the Video, large enough to accomodate the tires of all our Aircraft. The Cage was stationed in a Concrete Bunker type Room with Explosion proof Insulated Glass. NO ONE was allowed in the Bunker when the tires were being inflated! And it was said (never witnessed it), that if the Tire Exploded, that little Cage would never have held the Tire Shrapnel in! Thereby, the reasoning of a Concrete Bunker!

One of the reasons so much Damage can be done to an RV when a Tire Failure occurs going down the road!

By the way, I knew a couple of those Dummies in the Air Force, (just kidding)LOL!

Be very careful when working around tires and SPEND THE EXTRA MONEY and buy a quality TPMS system! It could save your life!

tom

First death in our division, during Desert Storm, was a young man who inflated a military truck tire, without a cage. Tire blew up. End of story.