I have a 26 in mtb tyre (Vuelta brand?, 10 years old) that I tried to fit on to 3 rims - each time I pump up the inner tube, it forces the tyre off the rim. this tyre is wire bead and is dead easy to fit onto a rim. This kinda tells me that there is a fault (made in Thailand does not inspire confidence!) with the tyre (maybe the wire bead has snapped) or it is perhaps designed for some specific rim? Anyone come across something like this before?