general problems of the 2002 Nissan Quest

Purchased new 2002 Nissan Quest on 12/201. Current millage is 26,000. All 4 tires have had tire separation. We replaced the first one on 7/03 with only 17,800 miles on it, the second one on 12/03, the third one on 7/12/04, and the forth on 8/22/04. After contacting the manufacturer (continental tires) they have made me pay for all 4 replacement tires. I have told them that I belive that those tires must have been defective. They said that they would prorate the tires, but why should I have to pay for their defective tires? if those tires wouold have been good they should have lasted at least 40-50 thousand miles. I have also had to pay to re-align the van. This is a second vehicle that, as you can see by the millage, is not used alot. All tires were replaced at tire kingdom in apopka, so I don't have the tire numbers you might need. They said they had to return them to continental for the warranty. The consequences could have been fatal on all four occasions. Twice we were driving long distance and could have had a serious accident on the interstate. Tire size p215/65r16 the replacement tires are the same as the ones before, but I don't want them! I don't trust them! what I would like is a new set of tires from a different manufacturer or at least repayment of the prorated money I had to invest plus the alignment which amounts to $224. 19.