2009 Ford Focus tires problems

Purchased vehicle less than a year ago, from a dealership. New tires were put on at that time. Mileage when purchased was 29000. While driving on snow and icy roads it would wobble and get squirrelly, which I attributed it to the lightness of the vehicle. There was no reason for me to suspect the tires as I have them rotated according to manufacturer specs, and no abnormalities have been mentioned to me by the dealer. However, last week I had an accident as a result of a worn out tire blowing out on a snowy road.

All of the hankook tires had tread separation. One was so bad that it separated all the way around the tire so that it was separated like a doughnut was on the surface. I always have the correct pressure but these tires were dangerous when they came apart. The tire repair person could not believe how bad they were. I kept the tires to show anyone about these hazards.