I never knew that a valve extender could fail?

I finally got around to installing my TireMinders on on my RV and toad this week.  While I already had metal valve stems on some of my tires I needed to replace the extenders from my rear inner tires.  I took it to a commercial truck tire shop who recommended that I use something called a Air-Flexx which he said he was now using for all commercial trucks and is guaranteed not to leak.

Before installing my TireMinder system I checked the cold tire inflation and carefully set it to within 1 psi of the recommended pressure.  The next day when I finished the TireMinder installation I notice that the pressure in my right rear tire had dropped by 10 psi from 90 to 80psi.  At first i thought it was a bad sender unit, but when I put the gauge on it I was surprised to find it now read 0 psi. I tried to add air, but I could hear none going in.  With 3 different gauges I couldn't get any reading on this tire.  One possibility was that there was a leak and that tire had deflated, but when tried the trucker method of thumping the tires both inner and outer tires sounded more or less the same.

Failing to understand how this was possible I took the RV back to the commercial tire shop. They also got no reading on this tire so they pulled the outer tire of this pair and removed the extender. I noticed then that the valve remains on the inner tire, but the extender is supposed to open this valve when it is screwed in place. It seems that this extender was not opening the valve on the tire itself.  They changed out this extender for a new one and all was fine

YOu got lucky. More often they leak rather than don't open the valve.

And yes. Failures are very common.

Yep. Valve extenders can indeed fail, and in more than one way. Two of our steel extenders have worked themselves loose in recent years, and spun around until they nearly came off. Now I reach down and tug on them before each trip to ensure that they're tight.

Kev

    Over the years we lost 2, and the first one cost me an inner tire and a week layover in Taos, NM as they had to special order the tire.  So, after learning my lesson, I've kept a careful eye on tire inflation.  That's the benefit of a TPMS system.

Ed

This is good to know, I will be checking mine regularly on my dually.

It only takes me about 3 or 4 minutes to get the rear wheel covers off so I can get to the valves.  The fronts I can get to without removing the covers.
I've seen enough extenders fail over the years that I'd rather spend that time than risk the extenders.

I've tried several different types and brands over the years.  In my opinion they all fail eventually.  I don't use them anymore.

Just last week while driving around Chicago the TireMinder on the right rear inside started showing low & then went to zero.  Expecting the worse I pulled over & found that the sensor was gone.  Upon closer examination it seems the end of the extender stem broke off & about half of the threads were missing (probably still threaded into the sensor somewhere on I-294). I unscrewed the extender, checked the air & found I'd lost about 20 lbs of pressure.  Kept going to the next truck stop where I added some air & chalked that up to another learning experience. 

After taking it back last week to have the Air- Flexx extender replaced I was surprised to see that the pressure was low again in that same inner tire.  I went to measure pressure in that tire with a gauge and it read zero.  I tried to add air from my compressor and again none would go in.  This morning I took it back to the commercial tire shop that installed this and they took it all apart again and checked the tire carefully for leaks to find none.  The brass extender showed no leaks and the same for the Flexx-Air extender mounted to that.  When, however, we put a pressure gauge on the extender we saw air leaking from the connection between the extender and the brass fitting to the rim.  They tightened things up again and remounted the tires and sent me on my way.  Let's hope that third time is really the charm and I have it fixed now.  Thanks to the TPMS I realized that I still had a problem.

Through this I wondered one new thing.  These monitors report tire temperature.  How can this work if one doesn't have a metallic valve extender?  Mine have a stainless sleeve in the center, but when people try to use TMPS with rubber valve stems I have to wonder how rubber stems can conduct enough heat to the extenders for those to work correctly.