Circuit_freak, what is the scope trace showing (motor, switch)? You mentioned this transient happens when the switch opens. If so, I would agree with FvW that your values should be adjusted, and you might also want to try using a diode snubber in addition to (or instead of) the RC snubber. This is essentially a flyback diode reverse-biased in parallel with the motor. If your scope trace is showing the motor voltage (the transient is coming when the switch closes), maybe it's inrush current and perhaps a series inductor would help.