coming down a 25% grade dirt road the brakes started to smoke and fade.truck in low gear o/d locked out speed kept to 10 mph .we had to stop and let them cool at 1/2 way point ,dirt road 4 miles long...
An actual 25% grade for 4 miles total distance? Unfortunately, I question that part of the OP's statement! A dirt road and that angle would be riddled with washouts constantly with even a simple or normal rain.