Hmm, learn something new every day. Looks like floating rotors can click and it's pretty normal. The drawing that I'm looking at shows the '06 Silverado has floating rotors. Probably just the rivets clicking. As long as the rotor and rivets are in good shape, there's nothing to worry about.
It also looks like you may, if you're really worried, check the rotor pistons for freedom of movement. If one side isn't free the rotor can get pushed to one side also causing clicking.
Disclaimer: this is not personal experience. It's just googling and may or may not be accurate.
2013 V Star 1300 Deluxe
OEM Tall Sissy Bar
Memphis Shades Fork Deflectors
Bridgestone Exedra Max Belted Tires
Baron's RSTD 7308 bar
Last edited by sparkn; 01-26-2014 at 11:22 AM.