Caution-Frozen Valve Stem Caps
 

Yesterday I wanted to check the tire pressure on my wife's BMW X3 that came wirth a tire pressure monitoring system (TPMS). When I tried to unscrew the first metal BMW valve stem cap it was frozen and the rest were the same. I couldn't even get it off with a pliar and may have stripped the head. So I called the dealer this morning and they said you should not put metal valve stem caps on a car with TPMS because they will freeze/rust in place. Trust me, it's TRUE! You should only use plastic or rubber valve stem caps. I also have AMG metal caps on my SL (my BS does not have TPMS) which explains why they are so difficult to unscrew. Just a heads up to avoid a future and potentially expensive problem.

y would they only freeze with TPMS? thats weird...

Steel valve stems vs. copper and rubber for non-TPMS cars. I'm told aluminum and steel under the right environmental conditions (e.g. we just finished with a lot of snow, ice and rain in VA) will bond and forge a very tight seal.

Well I don't have tpms but I have metal valve stems and that has never happen to me. And Its been cold up here and I've been banging pot holes left n right in Philly.

Why do you have so many cars?

Who??

Because I can.