I take my scissors to the pliable pie plate ones, just makes the hubs easier to clean when I wipe my bike down. They are supposed to keep you from shifting the chain off the cogs into the wheel but most derailleurs have a setting that won't let you do that anyways. I have yet to drop a chain off my cogs back there and I take that plate thingie off all my bikes even my cheapie commuter/hybrid. The reflectors on a road bike can be dangerous. Those wheels spin really fast and if a reflector comes off while you are going down a hill it's going to hurt someone. That's why they make you take them off in order to race. Plus they are really rinky dink too, they come off rather easily.