I have an 04 AT. A few months ago, i replaced my tires and ever since, every couple of weeks my tire pressure thing beeps saying that it needs air. i go out and check and it was significantly low and its always this one same wheel. i didnt run over a nail or anything but somehow its losing air. anyone knows why?

also if i change my stock 16s to stock 18s, can i use the same tpms on my 16s? or do i have to buy new ones? thanks

 

no one here from across the internet can diagnose why your tire is leaking air. take it to a tire shop for diagnosis

 

Could be a lot of reasons for this problem; take it to a tire shop and have them check the tire for leaks, they have the proper equipment to do it.

Your old ones will work.

 

But if there was a wager involved in guessing what your issue is, I would be betting that the TPMS Sensor valve in the tire that won't hold air is your culprit.

...And while on the subject, did you happen to change out the valve cap on that stem with anything other than a plastic cap?

 

yeah one my original black caps went missing so i replaced them all with metal caps.

 

I'm with Voodoo on this one. I would bet that the issue is that the grommet on the original TPMS was kinda jacked up when it was taken off the one wheel and put on the other. Either that or it was fine when taken off, but the grommet(which is crappy) didn't seal real good against the inside of the new rim. Don't ask me how I know!

They actually changed that grommet on the newer TPMS units, but they still have to be used with extreme caution.

This is a crap picture, but you will get the idea. Don't pay attention to the yellow grommet or the little green lip as you won't have those, but it is how I solved my issue. I had aftermarket rims in which the hole was slightly bigger than stock on the outside of the rim and was getting leakage at the spots in green. I had to add a grommet(yellow) on the outside of the rim. The grommet in red is the original one and is inside the rim...this is where you are probably leaking. I would lose about 10lbs each day until I added the other grommet. Your issue is likely that the grommet got compromised during uninstall or during installation.

I eventually solved my issue upon my next tire change as I bought new TPMS's(new grommets) and told the guy not to mess up the grommets when installing and make sure they were flush this time!

 

Then another watchout to keep in mind here. Different metals in contact with each other over repeated heating and cooling cycles will cause a metal stem cap without any kind of plastic liner to basically "weld" itself to the air stem.

When you try to remove the cap after this has occurred, you have to apply an excessive amount of pressure/torque which can damage the TPMS sensor grommets or the valve stem itself resulting in air leakage.

If your going to use any kind of aftermarket metal cap, make sure they have a plastic liner inside the cap to eliminate metal-to-metal contact.

 

How do you know you didn't run over a nail?

I'm with the guys who said take it to a tire shop. They'll dunk it in their water trough and see where the leak is.

Or maybe just visually inspect it and find the nail.

Ken