Vehicle-only franchise:
Transformers is a toyline franchise made by japanese toy company Takara and american toy company Hasbro. Transformers is about alien robots, who came on Earth because of the war that appeared on planet Cybertron. The robots had an ability to transform into cars and other vehicles in order to be unnoticed by humans (I mean, some of people in the series don't mind see their true forms).
Transformers became a huge pop culture phenomenon after the success of the toylines, causing the franchise to spawn many movies, cartoons, video games and etc. Plus, it's considered as Hasbro's flagship franchise due to being one of most popular Hasbro franchises that many people know around the world.
First vehicles:
1. Optimus Prime (1987 design) (Kart)
2. Bumblebee (2007 design) (Kart)
3. Starscream (Wheelless bike)
Content ratio:
16 vehicles
2 wheels
3 race tracks