Year of Publication
O. J. Hahn
Weftless Bead design has long been in existence and still used in many passenger car, bus, truck and agriculture tractors. The ideal bead design is a high strength flexible cable with minimal cross section and covered by rubberized nylon, rayon or steel wire side wall. The basic tire bead designs are weftless bead with rubberized ribbon of parallel wires of multiple wound layers and a continuous wire wound in sufficient number of loops to give the required strength. Weftless bead failures generally occur within about 5cm from the end of the overlapping parallel wire ribbon. The cause for this failure is generally attributed to the mounting process in which the diameter of the tire bead is changed during the mounting process in the well of the rim. A finite element model of the tire bead was developed and under the known stresses of the mounting and final use conditions. The Weftless bead generally consists of five steel wires in parallel in a continuous rubber tape or ribbons, which loosely secures the wires in a soft insulating rubber. The ribbon is wound into a hoop with four courses resulting in a grommet composed of a stack of wires. This ribbon with ten cut ends forming a splice, with five at the inner cut edge and five at the outer cut edge. A continuous bead formed from a single wire does not have this failure prone splice region. Field data and the finite element calculations show the failure point of the weftless bead is almost always at the under lap or at the starting point of the weftless bead. Continuous wire bead have significant advantages in safety over the Weftless bead still used in tires.
Doradla, Arun Kumar, "FAILURE MODE OF THE WEFTLESS BEAD AND EVALUATION OF IMPROVED CONTINUOUS SINGLE WIRE BASED BEAD" (2005). University of Kentucky Master's Theses. 337.