If your running regular foams, water does indeed breakdown the foams. With closed cells this isn't a problem, however, there's arguably only one set rear closed foams worth running now the AKA red closed cell. The others are much too hard for most outdoor applications. This soon will change as proline and JConcepts are producing softer closed cells. I run a tiny hole on the outside of the tire and a standard 4-40 size hole on the inner. Just don't dunk the tires in the bucket. Ideally, using a bucket with a brush glued to the bottom and filling the bucket to just under the bristles of the brush works great for 1/10 scale tires.