Many RV folks find they need "more space" and when shopping for the "right" RV, they find themselves buying rig with duals tires, either a motorhome, or a pickup suitable for pulling that big fifth wheel. If you've never had dual tires, they're an experience, and sometimes take a little getting used to.
Not only do dual tires mean you'll be buying at least half-again as many tires for the rig when you "re-tire," they also require special attention throughout their life with your family. Let a "single" tire get a little low, you run some risks. Let your dual tires get low, they can actually rub against one another and cause damage to themselves. While we always admonish keeping a sharp eye out for tire pressure on any rig, that goes "double for duallies" if you'll pardon the pun.
But getting an accurate tire pressure read on a dual tire can be a frustrating experience. That's because "from the factory" a dual tire equipped vehicle generally comes with standard valve stems. On the "inside duals," the ones closest to the center of your rig, a short valve stem is "buried" in the midst of a rim, cleverly covered by the rim of the "outside dual." If you've got a skinny hand, you may be able to shove a standard tire gauge foot in and onto the valve stem to get a reading. If you're a large handed person, forget it!
Then take the valve stem of that outside dual. It'll be bent at an angle, and so thoroughly protected by the metal tire rim, you can kiss off any hope of making a "standard" straight shafted tire gauge reach into to get a reading. Here come the options:
Get valve stem extensions, especially designed for use on dual wheel vehicles. For the inside dual, a straight extension tube screws directly onto the existing valve stem, extending the "reach" out, maybe four inches. An angled (OK, "twisted") stem extension brings your access to the outside dual within reason. With these it's an "easy read" of tire pressure. They're not expensive--you can likely fit out a set of duals for less than $15.00. But hang on, there's always the "fine print in the contract."
First, valve stem extenders must be used ONLY on metal valve stems. Stick them on a rubber valve stem, and the motion put up by the extension will soon wipe out the air holding integrity of the rubber stems. Secondly, you may also have to hire the work of putting the new extenders on the rig--in some cases you'll need to remove the wheels to get them on. Some "do it yourselfers" will save the money and spend the time required to take the tires off and back on.
The real problem that tire professionals warn us about with valve extenders is that they reduce the integrity of the system. With a standard (non-extended) valve stem, you have two points where air can leak: At the "business end" of the stem itself, and likewise where the stem penetrates the rim. Add extenders and you add more points where leaks can (and often do) develop. And regardless of your stem, there will most always be a point of contact where the extender comes in contact with the rim. Time and vibration will most likely catch up and wear away at that extender.
What about using those flashy looking "stainless steel hose kits" that attach to your wheel hub? Again, the issue is reliability. The inside of that nice braided metal is a rubber tube. They do deteriorate with age, and "road hazards" can take a hose out in a flash.
What's the answer? Sad to say, one of those old "trucker's accomplices" is about the most reliable answer. It's called a dual foot pressure gauge. It looks like a longer version of the tire pressure gauge you might carry in your shirt pocket, only two angled feet allow you to both push straight onto the inside dual stem, and the other allows you to "pull" onto the angled valve of the outside dual. The "stick" indicator on these guys isn't spring loaded, so when your creaking back allows you stand up straight, you can adjust your glasses for a closer look of the gauge--it won't have "snapped back" into the gauge stem.
Filling duals is another issue. Not every service station in town will have an air hose fitted out with a dual footed air chuck. Best place to look for a place to "air up" your tires will be at a truck stop. At least there, they most likely won't charge you for the air!
All photos: R&T DeMaris