When did the problem show up? Was it all of a sudden or did it slowly become worse? Does the brake pedal move up and down when applying the brakes?You could have a problem with a brake calliper and or rotor.The car will pull to the side that is doing the most braking.If you have a calliper that is not applying properly it will pull to the opposite side.If you have a warped rotor it will shake the car when applying the brakes.Did it start after having the tires installed, if yes then the wheels could have been over tightened!Could be a CV shaft!You should take it to a shop that you trust!Give them as much info as possible on the history of the car and when the problem occurs.Get a written quote on the repairs needed.