I run a radar detector on my bike for one reason, not for speeding, but because a 1st gen seems to be pretty stealthy. Due to this, if you are coming toward radar and if you have someone a distance behind you, like a big SUV or truck, the radar will read them instead of you. Radar does not read who is going fastest, it reads the strongest bounce back of the signal. Occasionally, they will set up the radar units with a big screen beside the road to show how fast someone is going and I have found that I have to get pretty close before it will read me, if I am alone on the road. If traffic is a quarter mile behind me, I can slow down below their speed and sometimes it will not pick me up at all when I go by.
When my radar detector goes off, I will check my speed, but usually, I will try to see who is behind me and see if they are speeding.
RandyA