By Roger Marble
Sometimes my wife accuses me of being too negative because I seem to always come up with something negative about almost any topic. I really don’t consider it negative when I see there might be a way to make something or a situation better.
I guess it’s in my DNA to never be satisfied and always want things to be better, easier, safer or more durable. The simple act of checking tire air pressure is an example.
Pushing on valve stems can damage them
Each time you use a hand gauge to check air (morning of every travel day) you are pushing on the valve stem. If you have a standard short (less than 2″) valve stem, no problem. BUT for dual tire positions as seen on almost all Class A and Class C motorhomes there are either valve stems that have a bend in them or there are extenders of some type. Pushing on a bent or angled stem will place a torque on the stem mount in the wheel. This can lead to eventual degradation of the rubber seal between the wheel and the stem.
Here is what happened a few years ago to the tire of a friend of mine. He was not running a TPMS so got no warning that the valve stem developed a leak at the rubber gasket between the wheel and the stem.
The tire lost air and the steel body cords fatigued due to over-flexing of the sidewall, which resulted in the sidewall “blowing out.” Initially he thought it might be a “defective tire,” but when inflating the new tire it was discovered that the valve stem no longer had a solid rubber gasket at the wheel. So obviously this was not a “defective tire” – as any tire can fail if you do not keep the air in it. Soon after this he installed a TPMS.
If you have some type of extenders, flexible hose or hard line, you might end up moving or bending or even loosening the extender if it isn’t supported when you push a gauge or air chuck on the outer end.
An advantage to using a TPMS you may not have thought about
One advantage of running a TPMS that few people consider is that the TPMS gives you a pressure check each morning, as well as a continuous check while you drive down the road – so this eliminates the need to push on the stem or extender.
TPMS eliminates this torque force on the valve stem mount along with saving you the time needed to go out, get down on your knees, remove the metal valve cap, push on the stem and get a reading. Lots of fun if it is cold or raining. (Not.)
I prefer to just turn on my TPMS in the morning and, after my cup of coffee, look at the monitor on the TPMS and in a minute or two know the state of inflation for every tire.
No muss or fuss – plus the additional benefit of no torquing the valve stem mount.
Here’s more information on valve stems: Valve stems, cores and caps, “Oh my!” – And how tight is “tight enough”?
Read more from Roger Marble on his blog at RVtiresafety.net or on RVtravel.com.
##RVT969
You should always check the connection between the TPMS and the valve stem with a soap and water solution to make sure that it is not leaking so slightly that you can’t hear it. Also where the extenders (if used) attach to the valve stem. I recently had my tires replaced at a tire store that caters to trucks. They failed to properly tighten the connection between the extender and the valve stem. After 4 days as a sight, about half of the pressure had been lost and if it hadn’t been for my TPMS I probably would have ruined a brand new tire. I finally figured it out when it sat for a couple of weeks at home and went COMPLETELY flat, almost to the point of coming off of the rim. Fortunately it was a rear dual so another tire kept it from doing so. I was about to blame the tire mounting or the tire itself until I sprayed the soap solution on the valve stem and wha-la …. bubbles. I use about 25% dish soap and 75% water in a spray bottle to test. I keep this mixed all the time.
Just about any spray household cleaner, Windex, 409, etc., will bubble if there is an air leak.
I just removed and replaced the batteries in my TST tire sensors. When removing the sensors, I had 2 tires where the Valve was stuck open. I had to install new valves. This also happened when I first installed them. I only tighten to about a 1/4 turn past where air leaking out stops. Any thoughts? Maybe address this in an article. I have metal stems.
John, Yes people don’t realize that TPMS and Extenders do press on the valve core and as a result the core can get stuck. Your 1/4 turn is probably OK. You can learn more by reading my blog post on the topic of how tight. https://www.rvtiresafety.net/2019/03/valve-stems-cores-and-caps-oh-my-and.html