Is Moisture in tires a bad thing. Why with RVs?

The question of Nitrogen being used to inflate a tire has been covered in a few of my blog posts and on some other posts on the internet. It is often mentioned that the Nitrogen used to inflate tires is "dry" and so that is considered a positive but I don't recall anyone getting too specific on why "dry" is better than "wet". Before we get into that part of the discussion I want to be sure that everyone understands that any "gas" you buy in a high-pressure tank aka cylinder, will be "dry" as the process of separating the gas and compressing it removes the moisture. So if you were to buy a cylinder of CO2 or Argon or Helium etc the gas would be "dry.
I did a post in May 2012 as one of my early posts on How to get dry air for your tires by making your own air "dryer" for less than $20 for an almost endless supply any time you need it.
There are some companies that sell small cylinders of various gasses but you would also need to have a pressure regulator and a source of high pressure (1,000 to 2,000 psi) gas to refill your tank.

But back to the original question of why do we want to keep moisture out of our tires and why would getting "dry" or at least "dryer" air for our RV tires be advisable. By "Dryer" I am referring to the wet air you can get out of the "free" air at some gas stations where they might not maintain their air compressor or air dryer.

In the past when RV trailers came on Bias or tube-type tires we didn't worry too much about dry air primarily because the tube did a pretty good job of keeping high-pressure moisture out of the tire carcass plus those bias tires did not have steel belts and were probably just Nylon or Rayon cord.

The modern radials we use today are almost all "Steel Belted Radials". So the question is what happens when you "mix" steel and water?  The steel can rust over time. Now in most tires on your car or TV you may drive it almost every day. The driving generates heat and this heat is highest at the belt edge which would be the most susceptible to moisture. This heat tends to drive the moisture out of the tire rubber. However, if you let the tire sit for days or weeks moisture in the air can migrate into the tire structure. Moist inflation air can be driven into the tire structure and over time this moisture can attack the ends of the steel belts and form iron oxide. Rubber doesn't stick very well to the rusty steel so tears can initiate at the molecular level. Once cracks or tears are initiated in a tire they can only grow and if allowed to grow long enough or big enough you can end up with a separation in the tire structure.
Keeping moisture out of the rubber structure is why we also recommend you not park with your tires on wet sand or dirt and the moisture can migrate into the structure if exposed to water for weeks at a time.
Please don't jump to conclusions and say "Ya but I drive in the rain" or "Occasionally it rains and my tires get wet".  I am not talking about a few hours of exposure or even a few days. If you drive and heat up the tires it will drive the excess moisture out of the tire. It is weeks or even months of parking in a wet situation that we want to avoid.
Not inflating your tires with wet air (if you get water drops spitting out of the air hose it is way too wet to use except in an emergency) is what we would like to do. If you remove your valve core and what looks like fog or steam or water droplets spits out you have too much water in your tires and this is under high pressure all the time so this can affect the life of your tires.

Many after market tire sealants are water based so using that stuff can hurt your tires.


So that is why inflating your tires with dry or at least drier air is a good practice.

##RVT946

How to get dry air for your tires

A good part of the discussion on the advantages of inflating tires with Nitrogen focuses on stable inflation pressure which seems to be of concern to some. Now for race car application this is important and the benefits are meaningful in that application but I do not think that a fluctuation of a few psi due to temperature variation is meaningful in normal highway use. Measurable but not meaningful.

I can accept the fact that no matter what my opinion is, some will still argue that stable tire pressure is desirable, so they feel the expense and complications of using Nitrogen are worth the cost. While there are some theoretical advantages to inflating tires with a gas that is low on oxygen, I don't think they are worth the effort. I have both Argon and a mix of Argon and CO2 available to me in my shop but I still use regular air from my compressor. The one thing I do have with the air in my compressor is the knowledge that the moisture level is low, as I have filters and water separators in my system.

But what do you do if you don't have a well equipped shop in your back yard but still want dry air? I am going to show you a set-up I have, that costs about $20 and can be used to inflate your tires for years to come.

Above is a small air drier system I use in my shop for some special equipment that needs especially dry air, you can duplicate it to ensure the air you are using to inflate your tires is dry.

The dryer is available at 2/$20 at WW Grainger as well as $8 ea at Advance Auto. Be sure the one you buy is rated for the air pressure you need. Harbor Freight units are rated only 95 psi.

•The air chuck is under $2 at Harbor freight
•Quick connector set is $5 a set or less at Harbor freight.

Note my four year old desiccant is purple not blue so I am getting close to needing to change the dryer which is a disposable unit. To help keep your dryer from getting old fast, keep it tightly sealed in a good zip-lock bag or some container with air tight top as I do.

There are too many individual air setups for me to identify all the possibilities but this simple dryer will deliver what you need.

Warning. If you are going to try and "dry out" the air in your tires by changing your "wet" air you need to jack up the tire so it is not contacting the ground. If you let air out don't go too low or you may have problems with losing the seal at the bead. A quick test to see if you have lots of moisture in your inflation air is to remove the valve core. If water spits out you have excess moisture in the tire. You may even need a tire store to service it to get the excess moisture out.

Hope this will save money for those wanting dryer air in their tires.