GS 300 driving problems.
 

Hi all,

I have a 2006 Lexus gs300 and I just changed all wheels from winter to summer tires myself with a jack. Now when I drive the car it pulls to the right and when I brake it will pull one way or another too, it won't stop straight.
I also find that when I go over a bump or uneven pavement the car pulls sharply to the left or right and I have to hold on to the steering wheel hard to maintain control. I am afraid this will lead to an accident.

Any thoughts on what the problem could be?