Foam filling your new tires will make them virtually maintenance free = you will never have a flat tire again. I'm not too sure where you would have them filled, but it is worth the cost if you work around hazards that would otherwise make your machine useless. I like to foam fill new tires. They can add some more weight to the machine, too. That can help you out if your machine is operating close to its tip over point. The other obvious advantage is that the tires no longer squat under a heavy load. I've been told that the only two down falls of foam filled tires are 1.) the initial cost of having them foam filled & 2.) it can / does put extra pressure on the wheel bearings. Besides those two small issues, it is easily worth doing. With all of that now said, air filled tires are just fine too, though. It all kind of depends on what you will be doing with your machine. I really don't think BOBCATS come with foam filled tires, so that is a good indication of running on air only.