NEWTON, Iowa — A half hour earlier, Ross Chastain was smashing a watermelon in victory lane, triumphant and on top of the world. Another Cinderella moment for one of NASCAR’s favorite underdogs and he was enjoying every second, happy to regale everyone with a recap of his accomplishment.



The euphoria proved fleeting. The Chevrolet Silverado Chastain had driven to victory Sunday at Iowa Speedway failed to pass post-race technical inspection. And now Chastain was at a loss for words.



“I got nothing to say, sorry,” Chastain told The Athletic.



Having gotten word that his winning truck had not yet cleared inspection, Chastain witnessed the stomach punch firsthand alongside several Niece Motorsports crew members. When word arrived that NASCAR had taken away the win for falling below the required ride height, a mixture of disbelief and shock hung in the air.



Some members of Niece Motorsports muttered obscenities under their breath;...