In some cases it is necessary to plug a rubber or composite cover if balancing is required after a roll is covered, due to weight addition in the body of the roll. ... the wheel. With newer grinders, the wheel can be balanced in the grinder. Dia. Weight Speed (in.) (lbs.) (sfpm) Aiken, SC 72 144,000 9,000 Clarks Summit, PA 72 160,000 7,500 ...