T7 combat car was a prototype United States light tank design of the interwar period.
[1] After the T4 combat car had been tested, the Ordnance Committee recommended working on a road-track convertible tank design.
[4] Since the vehicle was – like the cavalry – expected to drive as much or more on the roads as off, the design featured a wheel-track layout capable of both modes.
In order to avoid that failure, the combat car was designed using three big road-wheels with rubber tires that also served as rollers.
However, in October 1939, the cavalry branch formed new requirements for their combat vehicles which specified regular tracked (not combined) suspension.
The ongoing war in Europe at the time proved that, in order for a vehicle to be successful, it needed a proper cannon.
In October 1939, despite its potential, the Mechanized Cavalry Board recommended further development and test of the T7 combat car program, and all other such convertible vehicles, be canceled.