Dually rear tire question. New tires steering sloppy.

There is the pressure issue as mentioned above, there is a chemical release agent on the tires when they are molded, this usually lasts a few miles though - can be exciting if the first few miles are in the rain. There is the fact that the new tires have much taller tread blocks then the replaced tires at the end if their life. The taller blocks flex more then the short warn blocks. I usually find that somewhere between 500 and 2000 miles I don't notice anything about the tires anymore.