The full wheel tubs were intalled for more than tire clearance. At first, the tubs were not going to be full width. At the same time I needed to find a place to put coolers for the transmission fluid & engine oil. The solution was to install full wheel tubs & then mount the coolers inside them on top of the framerails. Both coolers have fans to ensure adequte airflow. They also tend to make the truck sound a bit like a jet at idle speed.