TPMS Valve Stem Caps - Warning!
If your car has TPMS, and they all do since 2005, don't put aftermarket metal valve caps on the stems!
The stems require silver colored plastic caps, or nickel plated metal caps. If you use chrome plated caps, or metal caps made the old way then you may be in for a big surprise. I had to tow in a car today which the customer put metal replacement caps on two years ago. When he tried to remove the metal cap the valve stem snapped off, the core popped out and the tire deflated before his shocked eyes.
We tried every trick we know to get the other three caps off. We couldn't, they had become one with the valve stem. All four TPM sensors had to be replaced.
What is happening is that road salt is getting between the components and causing corrosion to accelerate. Eventually corrosion eats right thru the stem greatly weakening it.
Although I've read about this problem for a while in the trade mags, this is the first time I have personally encountered it.
So, a special advisory to you snow belt 'Festers; don't use those fancy looking aftermarket metal caps. You could get a rude shock one day when you go to add air to a low tire.