The watercart was fitted with three new rims and sent for a short drive before retorquing the wheels.
After a while, the operator noticed a strange smell that became worse.
The operator saw smoke coming from the rear of the truck.
The operator saw another water cart and called to ask the operator to look at the rear of the truck.
At the same time, the operator noticed spots of flames in a line on the haul road behind the truck.
The second water cart operator saw flames about 1m high on the inside of position 4 wheel.
They used the water cannon to extinguish the fire.
The NSW Resources Regulator said an emergency was called, and the watercart continued to cool the tyres.
"When changing to a different component supplier or to a different model component, a change management process must be undertaken," the regulator said.
"This must include checks to confirm compatibility with the equipment that is being fitted and for suitability for the task and duty."
