After about 40 mph the left side (driver side)presumably around the tire components, 

the car start shaking a little bit, the feeling is like the rim is not balanced or the rotor is defective, after I have changed rotors 4 times, and brake pads 4 times, changed tires rods and struts the car still having this problem for ever, the only time that everything is normal is when I change new break pads, but this last only about 1000 miles then car start to vibrating again, no mechanic here in Austin Texas can solve this problem, they check parts in the front and suggested to change what I did change, ( the brake pedal does not shake, only the steering wheel just a little bit when I brake over 45-50 mph, what the hell can it be? Any suggestions? I am going nuts with this problem. Thank you