The Variobar system allowing for variation of pressure in the air circuit is indispensable in any pneumatic tire roller.
Circuit pressure, and consequently wheel pressure, must be controlled at all times by the operator from the control station. The operator can adjust pressure as the wheel temperature rises or drops over time depending on work type, asphalt temperature and job duration. As the temperature rises, so does the wheel pressure.
Also, depending on the type of compaction required, the densities and a potential track mark problem, it will be necessary to increase or decrease the tire pressure to suit the course to be compacted.