Business is on a roll for tire re-treaders keeping big trucks operating on the rough gravel roads in the Bakken oil boom region of eastern Montana and western North Dakota.
    
Hi-Mile Tire Manager Al Rees tells the Billings Gazette the last three years have been the busiest for servicing and selling tires he's seen in three decades. The company ships about 250 tires a week to oil fields in peak months.
    
Rees says new tires cost about $600 apiece, while re-treads run about $200. On king-sized trucks pulling four-axle trailers and needing 36 tires, using re-treads can lead to a savings of about $14,000.
    
Experts say trucks hauling water or oil can re-tread tires about three times, while trucks hauling lighter loads on smoother roads can do five re-treads.