how long ago did you get the tires put on, how long are the stems, and what kind of wheels do you have? I ask because I've seen cracks develop in stems earlier than expected on medium and long stems (usually for steel wheels to extend past the hub-cap) because at high speeds, the stem bends outward from centrifugal force. I've also seen it from using the red/green pressure indicator valve caps (even on short stems) because they're so heavy. *this is over the course of 6 months+ tho. usually stems last 2-5 years (Depending on conditions)
1991 Toyota Pickup 22R-E 2.4 I4/5 speed
1990 Toyota Cressida 7M-GE 3.0 I6/5-speed manual
mechanic, carpenter, stagehand, rigger, and know-it-all smartass
"You don't get to judge me for how I fix what you break"
-over 1psi/month should be looked at.
-if a shop doesn't replace your valve stems with a new tire, take your stuff and get out.
-leaking or not, check your tires at least every month. that way you find out if you have a leak before it's visible (which is pretty low for most people).
I've found aluminum rims are usually OK for the first set of tires or 5 years. once they've been ground with a brushwheel to clean them or regular weathering for a few years they usually need to be cleaned/sealed every 2 years. (unless you have chrysler rims, then it's every 10 months. or chrysler chrome rims then it's every 3)
How do you go about cleaning and sealing them? I have gone through 2 sets of Chrome Lexus Rims so far in just about 2 years. After winter they're always peeling and if I replace the tires they will not hold. No matter how much I grind and how much I goop them they leak. At this point I don't care how ugly they are but a good way to clean them or some kind of paint or sealer that I can let setup before I put the wheel on (like creating a new sealing surface on the rim) would be great.
Everyone is shocked that OEM Lexus rims would do that, I have no idea, I just wish I got the Alloys instead but they're always pricey used when I look.