Crash bars are useful for reducing damage to motorcycle engines and body panels when it falls on the side.
Commonly, a crash bar is a loop of chrome-plated steel tube mounted to each side of a motorcycle’s lower frame. The crash bars stick out a few inches wider than the bike. These hit the ground and prevent the engine and frame from also making contact with the ground.
Crash bars are also believed to protect the rider. They have been known to limit damage to the bike and rider at speeds up to 30mph, for example, where the rider over-braked the rear brake, low sided, and slid along the ground. In that type of incident, crash bars can keep the bike from crushing the rider’s leg. These bars will also keep the rider from getting trapped under the bike in a parking lot tip-over. The crash bars will also make it easier for a bike to be picked up if it does fall down.
Lower extremity injuries are among the most common injuries sustained by motorcycle riders involved in an accident, according to a study on motorcycle crashes published in the Journal of Trauma and Acute Care Surgery (1994 Sep;37(3):358-64). These injuries can often lead to permanent disability.
Generally, lower limb protectors incorporate a crash bar and-or other device. In a study from Monash University, the need for a standard to ensure the strength of crash bars was noted. A number of studies that called crash bars ineffective appear to have included many “fitted crash bars were too flimsy or poorly designed to be effective.”
The general consensus is that an accident has to happen in just the right way for crash bars to offer any kind of protection. In some crashes, quoted the Monash study, “the leg often does not remain in the leg space during the collision events…. (Thus), conventional expectations of crash bar performance and leg injury mechanisms simply are not supported by the in-depth analysis of actual accident events.”
Leg protection devices, like crash bars, are thought to have the ability to protect riders against “serious leg injuries which result from direct crushing of the rider’s leg against the side of the motorcycle during impact,” said the Monash study.
Crash bars also work as mount points for accessories like highway pegs, lights and, on police motorcycles, sirens, radar guns and cameras.
In the United States, crash bars are not required on bikes.