Our t-shirt shooter, seen here,
http://www.chiefdelphi.com/media/photos/31867, is several years old but we are still running all the original wheels but one. They are solid, but wide and have a lot of rubber on them. After a recent upgrade to a four cim drive it runs with almost no problems on grass, pavement, and all floors.
Edit: I think they are old from am, but I'm not sure.