Just bought a 2002 Santa Fe, got the timing belt etc. replaced but have some vibration when braking at high speeds. My mechanic looked over it before I bought and said Rotors were rusty (front) and needed replaced. Dealer mechanic said rotors were fine - I'm confused. What else might cause this rhythmic vibration while braking - slows down as the car slows. Thanks.

 

Warped brake rotors are likely the cause. Sometimes a slipped tire belt will do this as well, but you already have one mechanic that thinks the rotors are suspect.

 

Rotors will get surface rust if the car sits unused for any long periods of time. They will even get rust when just sitting overnight if it's raining or very humid out. However, that rust is usually worn off by the pads after the first 3 or 4 applications of the brakes. If you are getting constant vibrations but only while braking, your rotors are probably warped and need to be replaced. You can resurface (cut) old rotors but they will be thinner and just warp quicker next time. Rotors are fairly cheap so I usually replace them instead of resurfacingthem.