The novel tire construction and tire-rim combination of this invention is specifically designed to permit the tire to be run-flat for a certain period of time without destroying the remaining useful life in the tire. It has been determined that the primary reason for the destruction of a tire when it is run-flat or deflated is the movement which the tire undergoes in going from the undeflected shape to the deflected shape as the tire goes through the road surface contact point, the "footprint". The Applicants have found that the greatest damage is caused to a deflated tire by the movement of the deflated tire sidewalls just before and after the tire contacts the road surface. This movement takes the form of waves or wrinkles that are created in the sidewall area of the tire immediately before and after the tire engages the road surface.
The damage is further increased if the deflated tire becomes partially dislodged from the tire rim so that the rim is no longer centered over the tire, what is called a "flip-flop" condition. This condition may also exist with the tire remaining seated on the rim by the tire wobbling on the rim from side to side.
All of these above defined actions in the deflated tire and its sidewalls generate a great deal of heat and localized abrasion in certain areas of the tire. This heat and localized abrasion result in irreparable injury to the tire.
The construction of this invention eliminates or materially lessens these waves or wrinkles in the sidewall area; it maintains the deflated tire centered over the rim so the flip-flop and wobble conditions are eliminated. This invention provides a stable condition of the tire and rim when the tire is deflated and eliminates these major causes of tire destruction when the tire is run flat. This construction also provides a safe, easily controlled run-flat tire so that the driver may come to a safe stop and then continue to drive until he is out of danger or has reached a place to implement repair of the tire.
It has been determined that these waves exist in a bias tire and in a radial tire; although the waves appear to be less severe in the radial ply tire.
The demand for a tire which is capable of running flat without destroying its remaining life has intensified recently for two reasons. First, the realization that critical materials must be conserved and must fulfill their maximum useful lifetime, and secondly, the plan to eliminate the spare tire in new automobiles. The tire and tire-rim combination of this invention meet both of these objects.