Removing or Overriding grid-container?

Hi, I have a header element that's full width and I would like the content inside the header (the menu) to have 100% width as well so it floats as far left as possible. The problem is that the .grid-container class was automatically assigned to the div inside the header:

<div class="inside-header grid-container"></div>

Is there a simple way to remove this class from the header or override its max-width for the header element only?