Rear beam symptoms

[aaron_one]

Hi everyone, this has probably been covered before but I thought I'd post fresh as I couldn't find a definitive answer. Just picked my hdi up today, it has 15 inch steelies on and the inside of the wheels seem to have been rubbing on the plastic, the plastic doesn't seem to be sitting flush with the actual arch but I'm not sure whether this is normal or the reason that the wheels may have been rubbing. I will try and get pictures tomorrow to show you if there is any camber. 
Are there any other symptoms for a failing beam? Noises, checks that I can do etc. 
much appreciated