I have recently noticed, after a trackday which was particularly hard on the brakes, that my front passenger side brakes are rubbing every so slightly. At slow speeds with the roof down you can hear the metallic noise of the pads rubbing ever so slightly on the disk. It's not enough to make any difference to the drive or build up an excess heat, it's just an annoying noise more than anything else at the moment. Is it time to replace the caliper before it starts to stick properly or could it be something more simple, and cheaper?