If the density of the beads is not greater than the density of the buffer, it will not be possible to pellet them no matter how hard you spin. If you can use a buffer of lower density, it might work. Alternatively, if the beads are of lower density than the buffer, you may be able to float them by centrifugation, then draw off the liquid ("subnatant") from underneath them.

Thank you very much Adam B Shapiro , I will give that a try