The present work was made with the purpose of studying the effect of speed increase on the values of draft. It was used a trailed disk plow. For the draft measurement it was used a coupling device in the drawbar, where it was inserted an electromechanical dynamometer PIAB. The tests were carried on field conditions, in soil of sand textural class. Four speed were used: 2,86 km/h, 3,61 km/h, 4,74 km/h and 6,64 km/h. Under test conditions, one equation was determined: K = 2,64 v + 62,88, were K = mean specific force and v = speed.