I also had to modify my power step running boards. The tire would rub when I turned into off angle drives or when I turned backing up.
Excuse the dirt......Its been $hitty Out. (and im lazy)
Before Mod
Modding Begin....
Had to cut the one piece plastic step cover right along the raised moulding (creating a end cap for the step)
Finished the last 1" or so with a utility knife so I didnt cut the extruded aluminum that the plastic step cover fits into. I tried to use the cutoff wheel for the whole thing an slightly cut into the aluminum at first. It wont be visible once the "end cap" that im making gets screwed back on. (Apologies for fuzzy pic)
Here is the under side of the front cap that I removed....I took a sander to the raised edge to smooth the plastic and clean up the cut from the cutoff wheel.
Trimmed 3/8 to 1/2 of the aluminum step
Test Fit of end cap.....
Good To Go
Before
After