I recently had my pads a rotors changed.. I notice while braking after a cold start I would get a clunk/knocking noise from the rear. I had both calipers serviced before them being re-installed. Both rear calipers are new because of the previous ones seizing up separately months ago. I haven't noticed any symptoms of the calipers seizing.. No burnt pad smell from being stuck, no extra dust, or unusual heat/wear coming from the rear brakes. I've read that sometimes a knock or clunk could after cold starting could be the ABS engaging? I never really noticed this much in the past and could use some ideas.