Ramps will slide out on concrete weather it is painted or not , trust me I know. When I had my Mini I was backing it up ramps , when I was almost at the top one of them slid on unpainted floor & I ended up going past the stop on the other with the ramp under the floor & wheel dangling in mid air. Lucky the back of a Mini is light & we could lift it off. After I always put rubber sheet under the ramps. [bigwhistle]

