I hear a loud rhythmic knocking noise when braking, sounds like it is coming from the right rear. No vibration, or feeling in the pedal, vehicle seems to stop normally, just the noise. And it mainly occurs when the road is wet or perhaps for a day or two after rain. After several dry days, no noise. I'm wondering whether it could possibly be something to do with the ABS system/sensors. No ABS light on the dash, and when I slam on the brakes in the rain the ABS appears to function properly.