Valve stem extender potential problems

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.

 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 RV 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 re even loosening the extender if it isn't supported when you push a gauge or air chuck on the outer end.

One advantage of running TPMS that few people consider is that the TPMS gives you a pressure check each morning, as well as continuous as 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 time 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.

 

I prefer to just turn on my TPMS in the morning and after my cup of coffee look at the TPM monitor and in a minute or two know the state of inflation for every tire.

 

No Muss or Fuss and the additional benefit of no torquing the valve stem mount. 

##RVT969

 

What inflation should I run ? Motorized vehicles

 The question as asked is simple but of course I have to make the answer complex.

Not really. However there are two different answers. One is for "Motorized vehicles"  Class-A, Class-C Class-B and tow vehicles. The answer for trailers be they tear drop or triple axle 5th wheel trailers has some minor but important differences. This post will address the Motorized Vehicles so I don't have to keep switching back and forth.

Step 1: Learn the ACTUAL load on each end of each axle. This should be done when the Motorhome or truck is loaded to the heaviest you would ever load it.

Step 2: Using the heavier end load number for each axle, consult the Load & Inflation tables for your size and Load Range tire, to learn the MINIMUM inflation required.

Step 3: Add 10% to the number is step 2. This so you are not chasing inflation every time the ambient temperature changes.

Step 4: Set your LOW Pressure warning level on your TPMS to the pressure in #2 minus 2 to 4 psi. (Note this variation is to account for gauge and TPMS pressure reading variation). We want the warning to sound as soon as we might be overloading any tire.

Step 5: Using your hand gauge, that you have checked against your personal digital "Master Gauge", set the "Cold Inflation" pressure for all tires on an axle to the same pressure, which would be the pressure in Step #3. NOTE "Cold" only means the tire has not been driven on or been in direct sunlight for the previous two hours. This means the tire is at "air temperature" or the "Temperature in the shade".

Step #6: Get in your vehicle and you can now drive.


Information. The +10% is to give you "wiggle room" for day to day changes in air temperature. We want to "Protect" the "Minimum" inflation number we learned in Step #2 while at the same time not have to get out and fiddle with tire pressure every morning. Each morning when you get up, you can turn on your TPMS and make your coffee. After a few minutes you can then read the TPMS monitor and as long as there is no unexpected pressure change (drop), you can be satisfied that all tires are sufficiently inflated. You may see a slow drop in pressure over time even when there is no change in temperature. A drop of 1 to 2% per month is normal fol all tires, but once you follow this guide you can probably expect to only need to add air once every two to three months. For folks needing High Pressure ( 80 to 130 psi ) this means you can plan to "top off" your tires at the next truck stop where they should have plenty of air at the pressure need.  I will cover adding pressure to a hot tire in a separate post.

Example: Following the above over my travels from Ohio to Oregon to Calgary to Glacier and home over a two month period, I only needed to add air one time at Yellowstone and I only needed to add about 3 -5 psi to my LR-E tires to get back to my +10% number in Step #3.

Comment: After a while you will learn that the inflation numbers in your tires are reported as slightly different than seen with your hand gauge. This is normal as most TPMS are rated at +/- 2% for pressure accuracy. The primary job of a TPMS is to report a pressure drop Not to report extremely accurate pressure. I would feel that if your hand gauge reads +/- 2 psi from a reference gauge that is good enough. If your gauge is off by 5% of your tire pressure goals you might want to get a better gauge.

Please do not forget the above is specific for "Motorized Vehicles" and not for trailers or dollies you pull.

If you pull a dolly I might treat it more like a trailer with higher inflation than Minimum +10% but that is a separate topic.

##RVT968