This study evaluates the cost and carbon impact of wheelset replacement due to wheel wear in a fleet of 1,109 iron-ore freight wagons in Northern Sweden. Using maintenance records from 2020 to 2022 and Weibull reliability models, average replacement intervals were estimated at 641 days or 110,382 km, corresponding to 632 to 1,065 wheelset exchanges annually across the fleet. The associated impact was estimated at 119,000 to 200,000 kg CO₂eq and €1.9 to €3.2 million in annual maintenance costs. The analysis also identified a small group of high-impact wagons with unusually frequent wheelset replacements. Bringing these wagons closer to fleet-average performance could reduce emissions by 22 to 27 tonnes CO₂eq and save €0.35 to €0.42 million per year. The results demonstrate how maintenance data can support targeted actions to lower both costs and environmental impact.