¡ñ 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 heatresistance limitation, it is essential to define a rated load. Tyre should run under operated conditions to avoid high temperature.
¡ñ Working capacity of OTR tyres is calculated by"tonkilometer 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¡æ, the formula for TKPH calculation should be adjusted as following,
TKPH nom
TKPH = ¡ª¡ª¡ª¡ª¡ª¡ª¡ª¡ª¡ª¡ª¡ª¡ª
1 + (Ta ¨C Tnom) *0.0096
¡ñ Example for the calculation of maximum working capacity
TKPH of tyre 27.00R49(E4) Load of a dump truck
Load per tyre (kg) 
Front axle 
Rear axle 
Empty Truck 
14480 
8500 
Loaded Truck 
25320 
25320 
Average tyre load Qav = 0.5(14480+25230) = 19900(kg) Average working speed of a dump truck, km/h
2L ¡Á n Vav. =  t
Average working speed of a dump truck, km/h V= 6.45¡Á52/24=13.975 TKPHnom=19.9¡Á13.975=278 Considering the ambient temperature, we should revise TKPH as below formula if necessary. TKPH£½TKPHnom /[1+(TaTnom) ¡Á0.0096] If the rated TKPH of 27.00R49(E4)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).
