Steering wheel starts to vibrate at 55 mph vibration goes away at 65 mph or if i maintain 55 to 65 mph while applying pressure to the brake pedal vibration stops. also when drive over a curb, (e.g.backing out of driveway or entering driveway with a normal sidewalk and gutter) there is a sharp thud in passenger side front tire. tires are not out of balance, alignment is fine,

I would suspect somewhere in your front end you have a compliance bushing with excessive movement. these cars front ends depend heavily on these style bushings, and as they wear you can start to see tire wear patterns, looseness in steering, and high speed vibration. make sure you have the front end inspected by a shop that is familier with these types of cars. good luck!

I have a 92 BMW 525i that made a thud noise when I tapped the brakes quickly and let off. Did it at any speed. Replaced the upper control arms, also known as thrust arms at AZ... about $120 each. Fixed the thud issue. Wasn't complicated. The RS ball joint was bad and both bushings were bad. Gotta replace both arms at the same time.