One of my rear tires with OEM 19's keeps losing air and setting off the tire pressure monitor. I've got 275-30 Bridgestone S03's and there isn't any visible holes anywhere. I lose about 15-25 psi daily. Could it be a rim leak? If so, can i still use the same tire and just take it to BMW to get it fixed?

Same thing happened to me....on my

Jeep Cherokee: Dirty RIM and Tire seal. Discount tires dismounted the tires, cleaned the wheels and resealed for FREE. :)

X5 4.4 : The valve stem had a small crack. BMW dismounted the tires and replaced the valave stems for FREE. :)

Check the valve stem.

is it a 3 piece wheel, because if it is maybe the rim seal is bad. just a suggestion.

its most likely a bad bead seal. just take it in to your nearest Americas Tire co. or Discount Tire, they'll dunk your rim and figure out exactly where your leak is coming from.

One of my rear tires with OEM 19's keeps losing air and setting off the tire pressure monitor. I've got 275-30 Bridgestone S03's and there isn't any visible holes anywhere. I lose about 15-25 psi daily. Could it be a rim leak? If so, can i still use the same tire and just take it to BMW to get it fixed?

15 to 25psi...that's huge. Either dunk the tire or spray the entire thing with bubble solution and look for the leak. I wouldn't take it to BMW UNLESS it's a cracked rim. Then you'd have to prove it's a warranty issue and all that. If you've got a local tire shop that can dunk the tire, it'll be very easy to find the problem. It may just be a bad valve.