A tire for vehicles offering low rolling resistance wherein the ground-contact surface area is variable as a portion of the tread part can be retracted and/or extended using pneumatic, mechanical or hydraulic force to withdraw from, or come into contact with the road surface before, during or after operation permitting more efficient operation wherein the material used within the tread part that retains contact with the road may generally have a smaller internal friction loss than the material used in conventional tires and the rolling resistance is thereby reduced when the retractable portion of the tread is selectively withdrawn from contact with the road surface furthermore achieving a smaller ground-contact patch footprint. The achieved object of a tire with a lower rolling resistance yields improved fuel consumption efficiency. Improvements in exterior and interior noise levels and a reduced tendency to exhibit hydroplaning action are also attained with a variable groove volume to tread surface-contact ratio. Within one embodiment of the present invention, an automated microcomputer-based tire control system is disclosed useable to command the motion of the moveable tread portion of the said tire in response to various operational scenarios.