Hi djvant. Welcome to the forum. Shaking can be caused by a number of things, (typically not misalignment), but thanks to your dandy clues and symptoms, this sounds like an intermittently sticking front brake caliper. One of my cars is doing exactly the same thing right now, but only after applying the brakes like normal. If I baby it and downshift to slow down, I can prevent the shaking.
What you might notice too when this occurs is the car will pull to one side when you let go of the steering wheel. It will pull toward the same side that smells hot. Another clue is when the shaking is not occurring, the car may pull the other direction under very light braking because the sticking brake is not applying.
If your mechanic can catch it when the brake is locked up, he will try to open a bleeder screw on a caliper to see if it will release. Usually it will not. That points to the caliper as the culprit. If it does release, pressurized brake fluid is trapped and can't flow freely back to the reservoir. Constricted rubber hoses are common on some cars. Brake fluid contaminated with petroleum product can happen to any car. That will cause rubber seals to swell and grow past the return ports in the master cylinder. Fluid contamination is a real expensive repair, and it's much worse if you have anti-lock brakes.
Monday, September 13th, 2010 AT 12:17 AM