This invention is a control device to vary the contact conditions of the tread of a vehicle to improve driving functions, such as skid prevention, noise reduction, road surface protection or road marking, by the choice of the appropriate trodden tips in given road conditions. The trodden tips and connected parts are unified to make a unit which is attached or detached with a simple connection such as the insertion at a convenient position, which enables the device to function properly with a lowered safety factor, reducing the size only to avoid damages of the device and around.