If your motorcycle begins to weave while you are riding over rain grooves or bridge gratings, you should:

The weaving motion that occurs when a motorcycle rides over rain grooves or bridge gratings is generally not dangerous. If you experience weaving when riding over one of these surfaces, simply relax and proceed straight across the grooves or gratings at a steady speed. Trying to compensate for the weaving motion by zigzagging is more dangerous than riding straight.