 When he turned 18 years old in 2016, JR Motorsports began fielding the No.00 truck for Custer full-time, competing for the Rookie of the Year title.At Canadian Tire Motorsport Park during the Chevrolet Silverado 250, John Hunter Nemechek and Custer were battling for the lead when Nemechek bumped Custer before running both Custer and himself off-road, pinning Custer to the wall.