A gang reel mower comprises a plurality of laterally spaced front reel cutting units having gaps therebetween, each gap being covered by a rear reel cutting unit that spans and overlaps the gap on each side thereof by an overlap area. Each of the front cutting units is supported for rolling on the ground by a grooved front roller having a grooved portion and by a substantially smooth rear roller having a substantially smooth rolling surface that each extend substantially across the entire width of cut of the front cutting unit. Each of the rear cutting units has a grooved front roller with side shoulders on each end and with a grooved portion between the side shoulders such that the shoulders extend substantially over the overlap areas between the front and rear cutting units with the grooved portion on the front roller of the rear cutting units not extending substantially into the overlap areas. In addition, each of the rear cutting units includes a rear roller with a rolling surface is shorter than the rear roller on the front cutting unit such that the shorter rolling surface does not extend substantially into the overlap areas.