Ford certified the C-max as being tow-able 4 wheels down behind a motorhome. Their instructions state that the ignition should "off". in this state the brakes should not be active (unpowered). The problem is they sporadically become active (powered) then return to inactive for no apparent reason. With this happening there is no way to properly set a supplemental braking unit. Sometimes you are over breaking and other times not braking at all. It is very dangerous and caused me brake lockup three times on a major highway where I could not pull over. This episode destroyed a brand new set of tires. Ford is well aware of this issue but they refuse to recognize it. I even paid a Ford dealer to upgrade my firmware in the hope that would fix the issue. It did not! I also replaced my supplemental brake unit with another brand with the exact same result. I don't believe the solution is really that difficult, either the C-max brakes should be active or inactive when the ignition is 'off' and the vehicle is in motion. Bouncing between those states is extremely dangerous.

- Bakersfield, CA, USA