I have a 15mo Bullmastiff, and yes the Tire was in nickel sized bits all over my floor in about 10 minutes
To keep him occupied we use real shank bones, kongs with frozen peanut butter, bullysticks and occasionally he will chew on his Gallileo bone (Nylabone). I've recently come to the conclusion that he prefers the toys that he CAN destroy! The Gallileo bone we've had for months and there is little damage to it but he doesn't chew on it very often. We are on our second tire and it is already missing a fist sized amount of rubber. The kongs are still the puppy ones that he first had as they are only interesting to him when filled, doesn't chew on them after they are empty. Stuffies die a quick death but he is HAPPY. I have had 2 stuffies live a couple months- a pink hippo with a soft rubber exterior and stuffie middle, when the first one died we bought another
Real bones can provide days of entertainment as long as they are thick bones. He once had a neck bone(frozen) that he was able to bite in half quickly and swallowed some before I could get it. He threw up a piece of bone the size of a Twoonie---very scary! I have been told to buy go-cart or mini bike tires as they apparently last a long time, but I haven't tried or priced them out. Goodluck and let me know if you find anything.