Tire Bubble problems of the 2003 Toyota Tacoma

I have had 3 out of 4 tires purchased in 9/08 develop large "bubbles" at the rim and 1 one of them went flat. The others were noticed and changed and all tires had tears in them that were not visible when the tires were on the rim. The first tire had around 25000 miles on it when it developed a large bubble while we were traveling. The receipt from the dealership that replaced the tire said it had a cut in it. Last week another tire went flat after I had driven over 400 miles and this caused me to inspect my tires and I noticed a "bubble" that started on the rim of another tire. When I took the vehicle in I had to buy 2 new tires because both of these tires had tears or cuts 1 1/2 - 3 inches long that were visible only after the rim was removed. These tires had around 40,000 miles on them. I have contacted the dealer I purchased the original tires from and I am in the process of working out a resolution with them. The 4th tire has a "ripple" in it in the middle of the tire, not around the rim, and the dealership has told me that is from separation and is not unusual. I am also asking that they replace that tire for me. I still have the last 2 tires but will have to give them to the dealership when we work out a resolution.