Traction device for vehicle wheels

A wheel for mounting to a vehicle comprising:

• a wheel hub and a tire mounted on the wheel hub, said tire having a primary chamber that is inflatable and in the inflated condition defines a circumferential portion for contacting a road surface;
• at least two stud bearing tread segments in spaced apart relation provided on said circumferential portion of the tire and at least one non-stud bearing tread segment interposed between the stud bearing tread segments;
• and
• a secondary inflatable chamber associated with the stud bearing tread segments and an inlet control selectively providing the inflation and deflation of the secondary chamber whereby the studs of the stud bearing tread segments are placed in contact with the road surface and out of contact with the road surface in response to the inflation and deflation of the secondary inflatable chamber;
• said stud bearing tread segments forming the side edges of the circumferential portion of the tire and in a state of deflation of said secondary chamber, said side edges are drawn inwardly of the remaining circumferential portion.