Skid aid for tire which generates substantially less friction against asphalt than rubber does

An annular tyre overlay (11) for drawing onto the rolling surfaces of tyres (40), which has a tread (17) on the outside, and a gripping surface (15) on the inside, of an overlay strip (13), which overlay strip is so designed such that contact between the rolling surface of the tyre and the surfacing of the road is prevented by the overlay strip (13) when the tyre overlay has been drawn onto a tyre (40) which fits,

• wherein a flange (21) continuing on from the overlap strip (13) is present which can be brought into abutment with the side of the tyre,
• wherein the overlay strip comprises a plastics material which generates substantially less friction against asphalt than rubber does,
• wherein the gripping surface is patterned,
• wherein the patterning of the gripping surface is configured to prevent displacement of the tyre overlay in a first axial direction which would cause an increase in a distance between the flange and the tyre, and
• wherein the patterning of the gripping surface has teeth which have a steep side and a shallowly-sloped side, wherein the steep side reverts displacement of the tyre overlay in the first axial direction, and wherein the shallowly-sloped side permits a displacement of the tyre overlay in a second axial direction opposite to the first axial direction, which causes a decrease in the distance between the flange and the tyre.