I think you must not be seating the bead of the tire properly and perhaps pinching the tube. The other possibility would only be that your gauge by which you are measuring your tire pressue is way off and you are pumping the tires up to an extreme presure. I always add about ten more psi than recommended by the tire sidewall and never have any problem. I have only had one tube distroyed in a blow out and that was because it was pinched under the bead. Your case is unusual and you are doing something wrong.