A little background:

my passenger side front caliper was seized so I decided to replace both of them + change the pads and take the rotors to get turned. While I was at it my father in law and I decided to replace the idler arm as the bushings were gone and it was making a creaking noise whenever the steering wheel was turned. The car was fine for most of yesterday until last night when I noticed a knocking/rattle sound from the passenger's side (very similar to horse hooves). I've checked the idler arm and the wheel studs in case they were loose but they weren't, any ideas? The noise doesn't seem to change with speed and is not constant (or rythmic) Any help would be appreciated.

Luis

 

Caliper bracket bolts? Bearings loose? Look at every nut&bolt that was involved in the previous repairs. You might be missing anti rattle springs/clips from the pads being out.