Unit D19: Class 870 SP Forage Harvester w 1050s Posted on January 14, 2019 (January 14, 2022) by Alex Barrie in Compaction Test Results Datasheets Plot Comments These plots show the benefit of a CTIS system installed on a forage harvester.The harvester has a heavy front axle load and the high pressure tires can be lowered in the field to reduce the stress in the topsoil.