Piston-actuated wheel cover

A wheel cover comprising a body having a plurality of fins extended axially from a peripheral portion thereof, slot being formed in a free end portion of each of said fins, a ring engaged in said slots of said fins, a notch being formed in said ring so that said ring has a first end and a second end, and an expanding device including two tubes each having first ends which are integrally formed together, a bore being formed in each of said tubes for containing hydraulic oil, said bores being communicated with each other, second ends of each of said tubes being open, a piston being slidably received in each of said bores, said first end of said ring being engaged with said piston of said first tube, said second end of said ring being engaged with said second end of said first tube, an inner thread being formed in said second end of a second tube, a head being integrally coupled to said piston of said second tube and having an outer thread formed thereon for threaded engagement with said inner thread of said second tube, whereby said piston of said second tube can be caused to move into said second tube when said head rotates in one direction so that said piston of said first tube can be urged to move outward of said first tube and so that said ring can be expanded and so that said fins can be expanded, and said piston of said first tube can be pushed inward of said first tube by said ring when said head is rotated in a reverse direction.