On a 2010 X5 does anyone know how to mute the rear PDC sensors?

I have a Thule hitch mounted bike rack and the rear sensor constantly beep. I know you can turn down the volume in the IDrive, but the warning sound with the rack installed is still quite loud.

I suspect the same think happens when towing a trailer. Does the IDrive disable the rear sensors when the electronics are connected for a trailer hitch

thanks