Used to happen to me. I live in the uk and they spread grit salt on the roads in the winter so when it rains it lifts of the roads again and plasters your hardwear! Now I have a little tub of clear grease I quickly rub on the wheel nut n bearing before a ride. All the stuff sticks to the grease then just wipe it of when your done. Just don't get any on the wheels or you'll be bombing hills sideways faster than forwards!