I bought 90,000 mile tires for my car a little over 2 years ago. They've only been used for 20,000 miles and the fronts are almost bald and make it impossible to drive in the rain. They've been rotated once at 10,000 miles and I'm about to take it back for another one. Why would they wear so bad in such a short period of time? The car itself just hit 73k miles. I'd just like to be prepared before I take it in for a rotation because I'm sure they will bring up the fact that the tires are trashed.