Join Date: Jun 2007
Location: Twin Cities, MN, USA
There is one last thing to consider. Let's assume the wheel rim was formed from straight bar stock, bent into a hoop, and welded. (Or, maybe the rim is cast metal.) Maybe it is an imperfect weld, and air is escaping from the weld. Or if a cast rim, air leaking from a casting imperfection.
I mention this because I rebalanced my front wheel a couple days ago. As it slowly spun on the balancer jig, at a spot across the diameter from the valve stem I saw what appeared to be a slightly blemished spot, like what is left over after a grinder cleans and shapes a weld. Highly unlikely leak location, but not impossible. This weld joint, if this is what it is, should be visible on the inner face of the rim when the tire is off.
Air leak locations- valve stem and stem mounting, tire carcass, tire bead/rim seating, and the rim itself.