They're a design that worked but not as well as a rotor. They also tend to be more worn out than a rotor of approximately equivalent age. Finding one that isn't worn out is hard to do because how do you know until your watchmaker takes it apart? Nearly impossble.
The only reason to own a bumper is if it's a family piece or you'll wear it rarely. Rotors, especially the 550/560 series, have all of the kinks worked out, so to speak, and are much better for daily wear.
Tom
Click to expand...