Why Rodents are Chewing up Car Wires and What You Can Do to Prevent it. We live in farm country all around us and we use Bounce sheets everywhere in all three autos. But you have to change them every 6 to 7 months at most. They really do work. They chewed a bit out of a side to side thick rubber gasket just before the firewall. Dealer wanted $245 for a new one for my C5..