Big Dog Extreme 2021 Edition So why the Big Dog Extreme? Brand new model. Brand new riding sensation. The Big Dog Extreme is the epitome of power and modern design. This new GreenBike Electric Motion model will leave you breathless and feeling “Extreme”! Motor: 48V lithium-ion battery, and a 750W Nominal motor Brakes: Hydraulic disk brakes, and a bold powerful design. Tires: INNOVA Tires 20″ x 4.0″ front and rear, some of our thickest tires yet!