The vehicle is exercised in a bounce motion with some pitch angle introduced to achieve a differing amount of wheel travel front and rear. For example, if the chassis is pitched forward as it is bounced, the front will travel further than the rear.
During this test lateral and longitudinal forces, and aligning moments are maintained at zero at each tire contact patch, thus canceling any unwanted tire “scrub” forces, and allowing the suspension to move freely without binding. The slow speed of this test (cycle times are typically ~ 1 minute) removes unwanted damper and inertial forces from the tire vertical load
measurements. Corresponding loads, displacements, and orientations are measured at each of the four wheels.
Here are some characteristics that are measured in a Bounce-Pitch Test:
- Bump Steer
- Bump Camber
- Tire Radial Rates
- Track Width Change
- W/C Lateral Displacement
- Ride Rates (ground to chassis, includes tire)
- Wheel Rates (wheel to chassis only, without tire)
- Friction / Hysteresis
- Lateral Tire Center of Geometry (COG) Displacement
- Lateral Tire Center of Pressure (COP) Displacement