I just found that I have a second wheel where the outer ring of the chrome cladding is starting to crack. The first one did it a while back and I could hear a clicking coming from the front end somewhere. Turns out it was a crack that had apparently started due to the width of the 315s pressing on the chrome. Luckily I just bought some alloy rims to put my new 315s on.....

Check those rims...... The good thing is that it's not a sefety issue since it's just a chrome cover...

 

I've had the same problem with my wheels making a clicking sound as well. I'm running some centerline wheels which have a chrome center cap. From what the Les Schwab tells me is that because of the alloy wheel the wheel flexes alittle and the cap does not so the two do not mesh well together causes it to make a clicking noise. At first I thought it was my hub going out. But luckily it was just the wheels. I found a fast and simple solution which cured the problem. I took the center cap off which is held in place by two allen screws and ran a thin bead of clear silicone let it firm up and put the cap back on. I've had no problems sense.