It all started when Raymond Rice tried to buy a new tire for his tractor. The Westport, N.Y., hay and cattle farmer headed to a Vermont store where, he said, a salesman quoted him $1,800 for a single tire. When Rice learned he could purchase the same tire elsewhere for about $1,450, he thought the shop — which he declined to name — was ripping him off. So, Rice, whose haying operation was struggling, decided to go into the tire business himself. Last spring, the 52-year-old entrepreneur opened Rice Farm and Tires in a modest farm building not far from...