On my setup I have what I think is the linkage these came with when ordered from DC/ hustle stuff. I have the outboards kicking in when the center is about 40% open. I can drive all day on just the center. On the expressway It will go to 75 mph or so with the center at that 40% or so. At that point you will feel the extra resistance in the pedal... Push a little farther and BOOM your flying !!! You can see the linkage better in that link I posted