Checking Tire Pressure

A dial gauge is usually more accurate than the stick style.
Photo Credit: antti/flickr.com

One of the simplest, yet most critical—and far too often overlooked—RV maintenance issues is that of checking tire pressure. Even with fuel prices relatively low, we all can stand to see less of the fuel pump. By keeping your RV and tow vehicle tires inflated properly, you can gain as much as a whopping mile per gallon in fuel economy.

But a lot more is at stake: Under-inflation is a leading cause of RV tire failure. An under-inflated tire is a tire that will run hot. Running hot leads to dramatic tire expansion and can result in sidewall blowouts. Tires are expensive, but losing control and blasting Mo-Mo the Motorhome into oncoming traffic can just ruin your whole day.

First check your rig owner manual—it will show the specific recommended tires and their inflation rates. Lacking that, read the data stamped on the sidewall of the tire.

Now you’ll need to test your tire pressure with a GOOD quality gauge. Here’s where some controversy can pop up. Some folks like the “put it in your shirt pocket,” stick-style air gauge. They may have a point, but we’ve found the stick type isn’t always accurate. They often have the drawback of fewer gradations, making it difficult to know what the pressure is within less than five pounds. Here’s another case of spending a few more bucks, but spending it wisely. The dial-type air gauges are more accurate, and usually read down to the precise pound of pressure.

If you spring for the dial style, do take good care of it. Dropping it on the pavement can cause irreparable damage. When ours is not in use, we carefully put it away in the “glove box” (who—other than snobs maybe—drives with gloves these days?).

Beating both the dial gauge and the stick gauge? Often the electronic digital gauges beat these both, hands down. Why so? Digital gauges are less prone to problems associated with dirt and dust. They are also easier to read and interpret than either stick or dial. Yes, you do have to keep up with maintenance on these—you’ll occasionally need to change their batteries. “But what about price,” shouts the audience. Aha! It’s a gotcha!

Independent research organization Consumer Reports tested quite a number of tire gauges of all sorts. They tested them for durability, accuracy, ease of use, and how they reacted to ambient temperature. At the top of their ratings were two digital gauges. Accutire MS-4400B, which retails for just $10.99, and Accutire MS-4021B, which runs a buck less. If you think more money must mean better, well, they rated Intercomp’s 360060, which costs $55.95, as “very good” but found it only registered up to 60 psi, and for many RVers, that pressure rating would be too low.

Check your pressure with the tires COLD—that is, several hours after you last drove the rig. Driving as little as a couple of miles can lead to erroneous readings. Read the tire pressure for each tire, and compare it to the recommended pressure. Write down the specific tire, and the difference between the actual pressure and the recommended pressure.

Here’s a working example. We did a reading on a test vehicle, and one tire registered 64 pounds, cold. The recommended pressure was 80 pounds, so simple math tells us the tire is 16 pounds low. We’d then write down the tire position on the rig, and note it required 16 pounds more pressure.

Now drive to wherever you obtain air, and using your gauge, check the tire pressure again. Most likely it will read higher than when you started out. ADD the precise number of pounds each tire was low—even if this might appear to “over pressure” the tire. Tire readings are all based on cold pressure and allowances are made for road heat. NEVER deflate a hot tire to bring the pressure down “to what it should be,” just test them cold and adjust as needed.

In our case, by the time we got to the station, the tire read 66 pounds. We pumped the tire up to—not the “recommended” 80 pounds but instead 82 pounds because the tire was 16 pounds low when we first read it. That short trip to the service station added two erroneous pounds.

Keeping up with tire pressure is critical. One U.S. Government study indicated that in a single year, more than 78,000 crashes could be attributed to blown or flat tires. A leading cause of tire failure is directly related to under-inflation.

Listen to Russ and Tiña’s weekly podcast on a variety of RV topics at yourRVPodcast.com.

Russ and Tiña De Maris