How can contact pressure be adjusted on Pneumatic Tired Rollers?

• A. By adjusting engine speed
• B. By adjusting ballast and tire inflation
• C. By changing drum size
• D. By changing the vehicle height

Answer: (B)

Contact pressure on Pneumatic Tired Rollers is controlled by ballast and tire inflation. The downward load on the surface comes from the machine’s weight plus any ballast you add. Adding ballast increases the downward force, raising contact pressure. Tire inflation changes the size of the tire’s contact patch with the ground—higher inflation yields a smaller patch and higher pressure per unit area, while lower inflation enlarges the patch and lowers the pressure. This is how you tune the roller to the material and desired compaction. Engine speed affects travel and vibration duration, not the static pressure. Drum size isn’t a factor for pneumatic tires, since there are no drums to size. Vehicle height doesn’t provide a reliable way to adjust contact pressure. So ballast and tire inflation are the correct controls for contact pressure.