I just recently purchased a used set of oem 20's with the stock Pirellis with about 10k on them. Well 1 of them is losing 2 to 3 lbs of air a week. Has anyone else experienced this? I dont think the rim is bent, atleast it looks to be good and has no visable damage. I was thinking maybe have the valve stem replaced? How much does that run? Any help is appreciated. Thanks