Thanks again guys. I brought the wheel back to the installer (Farnbacher-Loles). They said it seems the leak is coming from the two halves of the wheel, as many of you had guessed. I must say, they've been taking their sweet time (going on a week now).

Is applying fresh silicone something I should have expected them to do prior to mounting the tires? Or is this a rare situation that I should feel comfortable paying them for?

 

Some good advice has already been given, but I'll throw my personal experience out there as well.

I recently had the same problem with one of my Champion RG5's. I checked EVERYTHING....replaced the valve stems, had the tires re-mounted, checked for nails...you name it!! I found no evidence of a leak whatsoever!! Some days it would hold air just fine, other days it would lose 5-10 psi in a day.

The problem was that I was checking the tire for leaks while it was OFF the car....when I should have left it on. The problem ended up being a very small pinhole size tear in one of my sidewalls. It only leaked when the pinhole was on the ground and the weight of the car was above it. So as the tire was rolling when I drove....pss....pss....pss....pss....pss, very little at a time. I finally ended up finding it because I had coincidentally parked the car with the pinhole exactly on the ground and the car had sat for two days and the tire went completely flat. I used a portable compressor to fill and and heard the leak.

Moral of the story: some leaks are so small they will only appear with the weight of the car above them. It's a PITA, but do the water/soap/windex testing with the wheel on the car.