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Enemies of a Tyre: HEAT

As a continuation of our “Enemies of a Tyre” series I would like to continue by discussing the effects of heat on an OTR tyre.

During normal operation tyres will generate heat. This is caused by the continual flexing of the tyre as it rotates. The more the tyre flexes the more heat it will generate. The more the tyre is forced outside its designed shape greater the fatigue is applied to the casing.

The factors directly contributing to the amount of heat generated through tyre flex are:

– Load
– Speed
– Distance
– Inflation Pressure
– Tyre Construction
-Rubber Compound
– Ambient Temperature

The hotter a tyre runs the less efficient it becomes and the more susceptible it is to damage. When a tyre runs hot:

– The wear rate increases
– It is less resistant to cutting
–  It increases the rate of casing fatigue
– It increases the chance of heat separation
– It increases the chance of cut separation
– It increases the chance of tyre burst
– The greater rate of repair failure

Haul road and pit design can affect the load on a tire

– Load transfer from cornering and road profiles make the tire work harder.
– Distances covered and average speed is determined by mine planning of waste and ore storage area locations.
–  Haul ramp profiles and corner super elevation all contribute to load transfer

Heat Generation

Flex is the generator of heat in tires and the other contributing factors affecting the rate of heat generation in the construction of a tire are:

    Tire construction

– The crossing of the casing cords in bias ply tires work against each other creating more heat compared to a radial configuration.

    Rubber Compound

– Various rubber compounds used in tires have differing heat resistant qualities.

    Casing Mass

–  The larger the rubber mass the less able the heat can dissipate from the rubber. Areas effecting this would be TRA code and tread pattern.

    REMEMBER

‘ The amount of work or flex or heat generated in a tyre will increase the risk of damage to a tyre. Heat damage is not necessarily instantaneous. Tyres suffering heat damage previously may appear to fail for no apparent reason later in their life.

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