In 1956 Petropoulos made a bold move, investing in farm tractor production. Model Π-35 introduced in 1956, as well as the more powerful Π-55 that followed shortly, were based on International Harvester designs (powered, though, by Perkins engines). Competitively priced and robust, these tractors became immediate success stories; however, in the early 1960s the company was engaged in a legal dispute over market (competition) rules with Malkotsis, another Greek tractor manufacturer claiming a share in the fast developing tractor market, resulting in production delays that almost bankrupted the company.The company eventually abandoned production of its own tractor series and focused on engine production and truck and tractor assembly (Petropoulos-assembled trucks and tractors were exported to Europe and the Middle East).
In 1956, Petropoulos made a daring investment in farm tractor production. The Π-35 model introduced in 1956 and the more powerful Π-55 that followed shortly were based on International Harvester designs (powered by Perkins engines).  The tractors were competitively priced and robust, becoming immediate successes; however, in the early 1960s, the company was embroiled in a legal battle with Malkotsis, another Greek tractor manufacturer, over market regulations. This dispute led to production delays that nearly bankrupted the company. The company eventually abandoned its own tractor series and focused on engine production and truck and tractor assembly (Petropoulos-assembled trucks and tractors were exported to Europe and the Middle East).