TYRE BEAD

The abrasion resistance increases considerably when reinforcing fillers are added to the polymer. This is, in particular, the case with rubbers incorporation of carbon black (e.g. 40 weight parts per 100 rubber parts) increases the life of a tyre bead from 5,000 to 50,000 or even 100,000 km ... 

The development has been commercialized (by DuPont) as a masterbatch for elastomers (for power transmission belting, hose, tyre bead and tread areas, bearings, packings, and seals) and for thermoplastics (for a wide variety of applications). A similar development has been reported by Akzo. 

In a pneumatic tyre, that portion of the structure which holds the tyre on the wheel it consists of a circular assembly of steel wires insulated with rubber, suitably wrapped and covered with rubberised fabric to enable the bead assembly to be built into the uncured casing. 

The reinforcing rubber and fabric around the bead in the rim area of a tyre to prevent chafing of the tyre by the rim. 

A shaped strip of mbber fitted between the beads of certain pneumatic tyre assemblies to protect the inner tube from damage by the beads and the wheel rim. 

Formerly termed braced tread, rigid breaker or belted tyre. A pneumatic tyre in which the cords of the casing plies run directly across the tyre section from bead to bead, and not at an angle as in a cross-ply tyre the breaker in a radial-ply tyre is an inextensible band which runs circumferentially round the tyre between tread and casing. It is made up of layers of bias cut fabric set at discrete angles to confer the required stability in the tread but maintain the flexibility in the sidewall. 

A tyre spreader is a device for holding open the beads of a pneumatic tyre so that the inside may be examined or repaired. 

Applied to a pneumatic tyre with no separate inner tube. An air-impermeable lining, usually of a halogenated butyl, is applied to the inside of the casing. The bead construction is such as to ensure an airtight lit on the wheel rim. Inflation is done through a valve fitted directly into a valve hole in the rim. 

In all tyres there are three types of components, the reinforcement layer(s), the rubber parts and the steel bead wires which locate a tyre to the wheel, or rim of a vehicle. Rubber is used in packing strips, inner lining, sidewalls and the abrasion-resistant tyre tread. 

A typical automobile tyre consists of several parts (Fig. 5). The tread and sidewall make up the outside of the tyre. The tread is the portion of the tyre that comes into contact with the road, whereas the sidewall, or wall, is the side of the tyre that connects the tread and the bead. The tread is reinforced from underneath by the belt, which comprises a set of fabrics and/or wires. The plies, found in association with the belt, are layers of rubber-coated cords, which are typically made of fabric, polymer, fibreglass, or steel. The set of belts and plies is often collectively referred to as the cord, or cord body, of the tyre. The cords of the tyre wrap around the bead, the part of the tyre that rests on the tyre rim. The bead consists of both mbber bead filler and a series of steel bead wires. The last major part of the tyre, the innerliner, is a low-permeability... 

Recent developments by DuPont in high performance car tyres have shown that inclusion of para-aramid as Kevlar EE, which is a pre-dispersed form of Kevlar pulp, in the rubber sidewall apex increases stiffness and improves cornering efficiency. The apex is part of the located radially outward of the tyre s bead (see Fig. 11.1 (a) and (b)). The EE stands for Engineered Elastomer and DuPont has introduced Kevlar EE into beltings, seals and gaskets, and bicycle tyres to improve resistance to abrasion, tear and puncture, modulus, and cut and chip resistance. ... 

Consider the cross-section of an unloaded tyre (Figure 7.8). The tyre is positioned on the wheel rim by the metal beading, the carcase or body of the tyre is... 

An estimated 2000 to 3000 people have been killed over the last twenty years, when 16 inch tyres mounted on wrong sized rims, have exploded, after being inflated. Up to 30 million such tyres are said to have defective failure-prone beads. The hazard does not exist in every 16 inch tyre, but as many as three quarters of the 16 inch tyres currently on the road do not have fail-safe beads. This comprehensive article supplies the details. 

Pneumatic tyre structure mechanics were analysed using non-linear finite element analysis. The deformation and stress-strain of all the components under inflation pressure of the tyre were predicted and the effects of three different bead structures on tyre performance were studied. It was found that stress concentration was the main cause of bead burst, separation and wear and that the tendency of the tyre to undergo early damage increased with decrease in bead rigidity. The study showed that the finite element method was an effective means of optimising tyre structure. 7 refs. 

Some criteria are presented for evaluating the various tyre design theories that are based on the equilibrium shape of the sidewall and on the rolling contour of a tyre. Tyre failure types and the mathematical models by which they can be predicted by modem theories of mbber/cord fatigue are also described. A tyre design theory based on stress-strain optimisation of its elements is proposed as is a hierarchic system of complicated tyre models for calculation of stress-strain cycles. Influence of the cross-section geometry and of the iimer stmcture of the tyre on stress-strain cycles in the belt and bead of radial tyres is investigated. 21 refs. 

The bead is usually a wound hoop of high strength monofilament steel wire coated with mbber, providing the tyre with a secure fitment to the wheel rim such that it does not move or dislodge as the vehicle undergoes severe manoeuvres. The bead and apex compounds... 

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