Just a thought... when you say rattle, and I know you said front, but I had/have the most annoying rattle...thought it was from the front, however after putting it up on the hoist twice and the mechanic not finding anything (had to stop him from whacking my exhaust system apart with his rubber hammer)... I took my fist and really whacked the bottom of my back wheel... straight up. Guess what... rattle, rattle, rattle. It was the rear brake pads rattling in their little slots. The garage took them off and put anti rattle stuff (like plastic/rubber compound) on them. They were great for about a week...then they started again. Try this even though it sounds like the front ( I drove with my head out the window for a few turns around a bumpy parking lot...hard to pinpoint).