I've been running EBC X-series rotors on my track bike since it's been a track bike. Floating rotors are known to rattle, but I was always under the understanding that the float is left and right. Most manufacturers put spring washers on the buttons to help prevent the rattle. My right side rotor is super loose. It not only moves left and right, but it's got play in the rotational direction. It's nearly impossible for me to measure by how much, but you can see and feel it. I would say it's at least three times as much movement as the left side. I've emailed the manufacturer, but anyone know how much rotational play is acceptable?