Front Bumper Dive During Maximum Braking of ABS-Equipped Vehicles

Passenger vehicle bumpers are designed to reduce collision damage. If colliding bumpers are not vertically aligned, their effectiveness is reduced and the resulting damage increases. Two bumpers of similar static design heights may become misaligned due to bumper dive caused by one or both vehicles pitching forward due to braking. Previous researchers have quantified bumper dive and how it changed with passenger vehicle designs. Currently there are limited data available to quantify the mean, variance, and distribution of bumper dive for modern ABS-equipped vehicles. We conducted maximum braking tests using 3 late-model minivans/CUVs (crossover utility vehicles) and 9 late-model sedans on contiguous dry asphalt and concrete road surfaces. Between 16 and 23 tests were conducted for each vehicle and all tests were conducted from an initial speed of about 65 km/h (40 mph). A laser distance sensor mounted to the front bumpers measured bumper height throughout each test. Overall, we found the average maximum front bumper dive of late-model minivans/CUVs varied from 7.8 to 9.1 cm (3.1 to 3.6 in) and the front bumper dive of late-model sedans varied from 4.3 to 6.3 cm (1.7 to 2.5 in). Steady-state dive was 3 mm (0.1 in) greater when braking on asphalt compared to concrete, but this difference was small compared to the variance observed between tests.