About a week ago, I had new tires put on my car. The next day, I took a long trip from Birmingham, Alabama to New Orleans, Louisiana. I made it to the Mississippi state line around the time my TPMS indicated that I had low tire pressure. After stopping and checking the tires, I pinpointed the tire that leaked but couldn't find a nail or anything in it. So I filled it back up to around 34 PSI and hit the road again. About 20 miles later, the pressure had dropped to about 25 again and did so every 20-30 miles after that. It was pretty late and all of the mechanic shops were closed, so I went ahead and used fix-a-flat and that took me to New Orleans.
Upon arriving, I went ahead and had the tire replaced (the mechanic wouldn't repair a tire with fix-a-flat) but on my return journey home, about 50 or so miles outside of New Orleans, the TPMS went off again and did so intermittently until I got to Hattiesburg, MS. There I stopped at a mechanic and they tightened my valve stem. I went about 20-30 more miles when the TPMS went off again and said screw it, filling up the tire every 20-30 miles.
The strange thing is, I stopped at an auto parts place and tightened the valve stem more myself, then I rode at about 60mph and didn't have any more problems until I started driving about 70 again after about 70 miles. I took the car back to the mechanic that first changed my tire before I left Birmingham, he dunked the wheel in water and couldn't find a leak and made the asinine suggestion that a kid was probably pranking me.
The thing is: I know the leak is there. I know it leaks faster when I driving at higher speeds, and I was wondering if anyone had any suggestions as to what the problem might be.