The first leg of the trip, I covered the suitcases with plastic trash bags, to protect them from the soot, which turned out to not be a problem. The rest of the trip, they were just hanging out there. No leaks, no soot, no problem.Oh, o.k. i thought that the weather tite cases were part of the rack and then you put your own suitcases inside of them. I dont think the mrs. wants her samsonite hanging out out in the elements. Maybe thats why God made garbage bags.