[Zebster]

I don't see how simply changing rear tyres could have caused the steering wheel to have become off centre. Assuming that the car isn't actually pulling to one side when driving along a straight road (a very slight pull to the left isn't unusual on a heavily cambered road) then I suggest that the steering wheel was previously left slightly off centre after the front alignment was adjusted for some reason? They are meant to accurately clamp the steering wheel straight ahead before making adjustments but this isn't always done with sufficient care.