Sounds like one of the front brake calipers is hanging up.
After you drive a few miles carefully check the temperature
of the wheels on both sides of the car (don't burn your
hand). Chances are one side will be much hotter than the
other. The car will pull in the oppsite direction (away from
the hot rotor). A few possibilities of why this happens -
bad brake line (acts like a one way valve and keep slight
pressure on the pads), caliper not properly sliding on the
slider pins (needs lubrication), trash in the caliper
blocking proper fluid flow (you can force fluid in, but it
doesn't bleed back properly); piston hanging in the caliper.
When a caliper hangs, the brakes on that side are always on
slightly. It might not be enough to notice at first.
However, after a few miles, that brakes get really hot, and
the braking effectiveness is decreased on that side. So when
you apply the brakes to stop, the cooler brake on the
opposite side works much better and the car pulls to the
side of the cooler brake. When you first start out, but
brakes work properly, it is only after a few miles that the
pull starts.

Ed

car pulls hard left.  I have had it back to the shop 4 times.  New pads,
new caliphers, new rotors, new seals, repack bearings, new wheel seals,
cleaned and adjusted rear brakes.  Car can be driven a few miles and it
will not pull.  All of a sudden when braking, it will pull.  If I slam on
brakes it doesn't seem to pull.  When I brake normally, i.e., traffic
light, stop sign, etc., it then pulls severely.  Anybody have any
suggestions?  Thank you.