I have BFG G Force tires, and Vintage Wheel Works wheels. The front tires both have very slow leaks, about 5 PSI per month. The rear tires are fine. I've checked the fronts for leaks by holding them in water to see if there are any visable bubbles and didn't see any. There are zero miles on them. Is there some sort of sealant I could use besides Slime? Actually, I think the aluminum wheels could be porous.