The mine site are prone to transport more and run faster to rise its output. Inevitably, tyre internal temperature will rise due to heavy loading. Tyre has heat-resistance limitation, it is essential to define a rated load. Tyre should run under operated conditions to avoid high temperature.

Working capacity of OTR tyres is calculated by"ton-kilometer per hour"(TKPH):

                                           TKPH=Qav x Vay

Qav= average tyre load =1/2 [(empty truck)+(loaded truck)] in kg

Vav= average working speed =[Circle distance X number of round trips] / Total working time, in km/h

If the ambient temperature is higher than 38℃, the formula for TKPH calculation should be adjusted as following,                                                                                             

                          TKPH nom                                               

TKPH = ————————————                                                                   

               1 + (Ta – Tnom) *0.0096                           

Example for the calculation of maximum working capacity:

TKPH of tyre 27.00R49(E-4)

Load of a dump truck

Average tyre load

Qav = 0.5(14480+25230) = 19900(kg)

Average working speed of a dump truck, km/h

                         2L × n

            Vav. = ————

                             t

Average working speed of a dump truck, km/h

       V= 6.45×52/24=13.975

    TKPHnom=19.9×13.975=278

Considering the ambient temperature, we should revise TKPH as below formula if necessary.

TKPH＝TKPHnom /[1+(Ta-Tnom) ×0.0096]

If the rated TKPH of 27.00R49(E-4)is 350, it is suitable for operating in above working condition because the tyre’s TKPH(=350) is greater than the real site TKPH(=278).