Twenty Eleven header problem

Hi,

I have created a child theme for Twenty Eleven for my site.

http://www.racenortheast.co.uk/

In the parent theme css file there’s a CSS rule that says:

#branding img {
width: 100%;
}

I however wanted my logo to have the following dimensions so I did this in my child theme stylesheet.

#branding img {
height: 100px;
width: 234px;
}

However, as you can see the image on the right has taken the same dimensions. Is there anyway I can change the CSS so it doesn’t dictate the width of my image and I can just set it in the HTML or let the browser show it at it’s default width?

Cheers,
Steve