Sunday, September 04, 2011

RV tips for filling dual tires

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

13 comments: said...

I have dual tires on my M/h.I tried in vain to check the pressure in the inside tires, to no avail. I bought a rubber type air extension fro an auto parts store. When I check my duallys
I screw the rubber extension on the stem and when I get the proper pressure in each tire I unscrew the extension and put it away.
Makes sense to me. It works every time.

PapPappy said...

I often wondered why not have a second valve stem on the inside of the inner wheel? sure, you would have to climb under the MH, but after spending 10-15 minutes trying to get at the elusive stem in between the two wheels, that might be a quicker option.

Yes, it doubles the "possible leak points", but if they are done correctly, or have metal stems, I think those points are moot.

Great blog! Thanks

PapPappy said...

I really like Curtmcree's idea....and plan to get myself an extension for that purpose.

Bill the Web Guy said...

What about those monitoring systems where you place a wireless transmitter on each stem? Are those worth the money?

Russ and Tiña De Maris said...


After having been "flagged over" on Interstate 90 in Washington State, and finding only "confetti" left on my now-useless rim, I'm thinking that those remote tire pressure monitoring systems may be worth looking into. Look forward to a future story on the matter, and hopefully a field-tested review of one of them.


keithnteri said...

Just had new metal extended valve stems installed. Also put a new tpms system on. It wasn't cheap but neither is replacing a tire in the middle of nowhere.

Had the hardest time finding the extended valve stems. Found them at

Fred said...

I have an F450 with dualies and solved my problem with stainless steel braided 7" valve extenders from Pacific Dualies available at: I've had them for two years and they work great. You'll want to get a set of rubber inserts for the hole in the outside rim to feed the extender thru. They are available at: for around $7. Pacific Dualies also sells a tpms tire monitoring system that I've had for a few months for my truck and fifth wheel and it also works great, available at: I bought it thru Amazon at a great discount.

bhbbrew said...

I have braided extenders on my dualies. They are on their second set of tires and I have never had a problem with them. For filling my tires I have a PSIclops XL-180 guage that fills two tires at a time allowing for an exact balance in both tires. I use a Tire Tracker monitoring system that does a very good job all the way back to the toad without using a repeater.

SolarSteve said...

Instead of extensions on the valve stem, I changed to "dually" valve stems seen in the Motorhome magazine back section ads. These are one piece metal long shaped stems that equal the stock stem plus extension, and are much more durable. This seems the safest way to add on a pressure sensor cap.

Ken Greenwood said...

I have a 3500 Sprinter with Alcoa wheels. Put new stems from and they are fantastic! Changes the job of cheking pressures from horrible into fun. Also a must if you want to put TPMS on inner tires.
Total investment after professional install was just over $200. My hands, knees and back all feel it was well worth the expense!

Brian Ralston said...

I had the braided extenders put on at the start of last year's camping season. I was at the Pocono 400 in June and was packing up on Sunday night when I noticed the inside right rear tire was flat. Called AAA, to no avail, so got on my phone and joined Coachnet, who immediately found someone to help me out (I, of course, paid for the service call because I didn't have Coachnet when the trouble happened and got reimbursed from AAA). It turned out that the valve extender was loose and lost all the air. Went back to the rv shop that put it on and had them fix it. Couple weeks later, I had the rv at the house preparing for another trip when the tire was low again. The valve was loose again so I took it off and haven't put it back on.

Anonymous said...

Two issues with my 2011 Ford F350 dually. First, an extender for the inside dually broke away from it's bracket and rubbed half-way through the side wall of the outside dual. Another few miles could have caused sidewall failure. Second, the bracket I bought for the second set is too small to fit over the thicker aluminum wheels. I hate to pay the price for TPMS but it will be the best way to go, and in the end will likely save me money.

C.Fin1964 said...

I solved my problem with leaking valve stem extensions by screwing them on to check my dual rear tires, adding air if needed, then removing the extender and placing it in my tool box. I used a 1/4 in. drive flex shaft screwdriver tool with a socket to install my valve stem caps. This may sound like a lot to do but a little extra time checking the air was well worth not worrying about the problem with valve extenders.