Brake shoes and drums can reach very high temperatures and take a long time to cool off! Once they've reached high enough temperatures to ignite the shoes themselves and any grease that may be in the area, the fire continues to re-ignite even after you've tried putting it out several times. The fire won't stay out until the brakes can be cooled down. So it isn't uncommon to hear about brake fires that end up burning the trailer to the ground because there wasn't enough water or fire extinguishers around to put the fire completely out. If you ever happen to see a tractor trailer with a brake fire, make sure the fire department is called. A fire extinguisher will not often be able to put it out.