on the way to the oktoberfest from florida i was going really fast a few times. along with a yellow corvette we were doing 110-120mph on the I-75 we stopped at a rest area and he noticed that my right rear tires losing air. I checked it and it was really losing air... so pulled out the spare. the 17" 275/40ZR17 barely fit into the spare area but that is oke' however when i was trying to find a tire shop in a middle of nowhere i started to figure out the problem myself there was no hole, puncture, nail or anything like that, so i assumed it is the valve core. I purchased a new one for $1.99/4pcs and replaced them. no changes, but found something strange. when i pushed the valve from side to side, and also when i just tilted it a bit, i heard the scary hissing noise. so it was a faulty valve installed by BMW dealer 5 months ago A Wal-Mart tire center refused to work on a 17" wheel a small tire shop closed at 2:ooPM finally a young guy at the gas station had fixed it in less then 2 minutes for a serius $5.00 labor (I also had a new valve from DAP 1.99/2pcs) less then 6 minutes and I was flying again on I-75 but this time a bit slower , around 90mph why did i told you the story ? just because i had never had a bad tire valve in my life (some 30 vhicles in 12 years) before and next time I have a leak, the valve is the first thing i check ! My tires are almost brand new, installed 5 months ago and had about 1,500miles... i learn new things almost every day ...