If they are brand new tires, then they probably still have the chemicals and such that tires companies put on to keep the tires from drying out and such. This chemical will rub off with use, but most companies recommend basically driving like a grandma until you have 500 or more miles on them. Check out tirerack for more info there is an article on this there. Othre than that, when did you get the car? Is it new to you also? If so you may be just giving it a little too much, but I would lay off for a while and see how it goes.
Could be crappy tires on top of the wear in period too.
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