Mine did (does) the same thing, made me QUITE unhappy the first few weeks I owned it - but some days it pulled left, and some days it pulled right on the same patch of road. So, I decided it probably was not an alignment issue.

So, after posting pretty much the SAME question, and getting pretty much the SAME answers, I figured it's what they say it is - them big ol' tires - and stopped worrying about it.

Now (since I expect it), I hardly notice it anymore.