Ok so i am new to the Xfire scene, just got out of the whole DSM thing (91 eagle talon Tsi) and i have a couple questions because i dont know anything about the Crossfire (well maybe some), but heres my problem.

I caught a flat the other day and had to drive on it about 1/2 a mile and let the car sit over night until i could fix it in the morning. So i go to a tire place and they sell me a Hancock 255/35/19Y rotational tire for the right rear tire that went flat. Now, i have the Contenentals on the 3 other tires that arent rotational and they are the 19CW not Y as on the Hancock. When i drive over lets say 40 i can feel vibration in my steering wheel and also coming from the back of the car and it gets worse when im on the highway. Is this due to the tire or is there other reasons this can be happening. I just want too make sure that it actually could be the tire before i pay $320 for a new one and i dont trust the dealership because they just want your car out of there. Any thoughts??? Anyone have this problem also???