i have a 96 bmw 318 ti . i have replaced the rotors and brake pads ,front and back. the problem is when i apply pressure to the brakes while driving , i can hear and fill thumping when braking .. could there be something else wrong with my braking. { a loud thumping noise when braking until i stop}

Check your tires. More than likely they are "cupped" or worn irregularly. This is usually caused by worn out suspension components and/or the car being out of alignment.

when u changed ure brakes, did you bleed the brake system?

i am sure that it is ok, but check ure abs too.

This same thing happened to me when I replaced pads and rotors.

Then I adjusted the emergency/hand brake as per the Bentley manual, and the thunking went away.