The reason for having the rubber so thick is that the cuts one is bound to get do not penetrate right through the rubber to the canvas or fabric, as I found it was really throught htis latter rotting that the trouble with the tyres occurred, whereas, when I had thick rubber, and particularly, be it noted, not one piece of rubber, but two pieces, namely, the rubber, cover proper and then a thick rubber band solutioned on top of this, I found from experience that, say, the rubber was half an inch thick, the cuts seemed to go much more easily through one piece of rubber than they did through two pieces of rubber, each a quarter of an inch thick, solutioned together.