Menu tab width, when page width goes below 1080px

Hi

Can i somehow make my 7 menu tabs equal in width and follow the webpage width if it goes below 1080px.(e.g older computers or browser halved on a Full HD screen.)

I’ve set the ‘Mobile menu collapse’ at 900px, but in between, the ‘orange’ and ‘red’ tap tends to drop below.

Thanks.

URL: http://www.beco.is