Breakover angle

Breakover angle or rampover angle is the maximum possible supplementary angle that a vehicle, with at least one forward wheel and one rear wheel, can drive over without the apex of that angle touching any point of the vehicle other than the wheels. This definition is contingent upon the wheels being in continuous contact with the supporting surface. Breakover angle differs from ground clearance, which is the shortest distance between the ground and lowest point on the vehicle.

Relevance

Breakover angle is a relevant performance metric in many common vehicle scenarios, including:

Off-roading.
Loading a vehicle onto a higher surface with a ramp.
Going over raised railroad crossings.
Going over speed bumps
Going over linkspans and ferry slips

If a vehicle drives over a breakover angle larger than what it is capable of clearing, the vehicle will contact the apex of the angle, which will quite likely prevent the vehicle from continuing any further in its direction of travel, possibly even completely immobilizing the vehicle.

Calculation

Assuming no tire deflection, and assuming an ideal breakover angle scenario, an approximation for the breakover angle of a vehicle can be calculated as follows: