Heres a good one !!!
 

So I recently put brand new tires on the HHR. Steel wheels, uniroyal 215/55/16, rubber valve stem with TPMS on the back. Had the mexican tire shop around the corner do it. He put new valve stems in also. When I lived in Beaumont I had a real tire guy, but have not found anyone very impressive up around Dallas yet. The mexican does very sloppy work. They whack the TPMS with the shoe of the tire machine if you dont stand over their shoulder and tell them. They never use the proper tool that threads onto the valve stem to pull it thru, they always just grab a pair of side cutters and pry it thru the hole, messing up the threads every time. If I had aluminum or chrome wheels no way in hell would I bring it to him. I know I really need to shop around. Here is the scenario and I know you are not gonna believe it. I put 40 psi in my tires. For a month I drive back and forth to work and the all hold 40psi +/- 1 pound all month long. I drive to Houston and the LR starts loosing pressure at a rate of about 1 psi every 5 minutes. Once it gets to 25psi, I pull over, pump it back up to 40psi and as I continue to drive to Houston down I-45 doing 80mph, it again starts to slowly loose pressure. I pumped it back up a total of thre times before I decided to try to drive in the slow lane doing 70mph. Guess what, I drove an hour and a half and it did not loose pressure. On the way back to Dallas I did an experiment and sure enough when I am doing 80mph, I loose air, when I drive 70mph I do not loose air. Why?

Yes, could very well be a dirty bead. I have been running 40psi, because I was having air issues prior. That's when I discovered the the tire valve stem was leaking. The valve stem was tore half way around right where it meets the tire. It would not even make bubbles when you spray it with soap, but if you tilt it just a tad it hisses. I had the mexi tire guy replace the valve stem, same thing, had them change it a third time and saw them run over the TPMS with the shoe (actually it is called a mount / demount head). It does not damage the TPMS, but it does kick the valve stem violently to a 90° angle, which tears it. Thanks OldBlue, I never thought about temperature being part of the formula.

I had tires installed Saturday at a Mexican owned tire shop . These guys were $100 cheaper than anyone else. Did it in 40 mins and did an excellent job. They will definitely get my business again. I ,in the past ,used a local guy in town until he had broke a TPS and blamed it on the part.