Tractor Ballast for a Target Weight-to-Power Ratio
The ballast to add or remove to hit a target weight-to-power ratio: target weight = ratio x power (hp), and ballast change = target - current. A 180 hp tractor at 125 lb/hp targets 22,500 lb, so an 18,000 lb machine adds 4,500 lb; a 120 hp tractor at 130 lb/hp targets 15,600 lb, so a 16,000 lb machine removes 400 lb. Field draft and tillage want about 120 to 145 lb/hp, higher-speed transport 90 to 110 (target 8 to 15% wheel slip): too much ballast wastes fuel to rolling resistance, too little spins the tires. The ratio, the front/rear split, and the tire and inflation ratings come from the operator's manual and the implement; a wrong number is a re-ballast.
Formula and source
target_weight_lb = weight_to_power_ratio x power_hp; ballast_change_lb = target_weight_lb - current_weight_lb (positive = add, negative = remove).
ASABE tractor-ballasting guidance (Agricultural Machinery Management) and the operator's manual, by name; the ratio, front/rear split, and tire ratings come from the manual.
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