What Are Motorcycle Crash Bars & How Do They Work?

In just about any fight between your motorcycle and gravity, gravity will be the winner. That’s why well-designed motorcycle crash bars are must-have accessories if you ride off-road. They can’t protect your bike in every situation––some falls are just too extreme––but if they do their job well enough that you can still ride home, you can chalk that up as a win for your side.

How Do Crash Bars Actually Work?

Engine guards protect the part of your bike that makes it go, and that’s a good thing since holes in engine cases or the radiator are pretty much show-stoppers. Elsewhere around the bike, crash bars prevent damage to bodywork, including the gas tank, which stops being a tank if the gas leaks out of a hole punched in it by a jagged rock.

What Are Crash Bars Made Of?

The material crash bars are made of says a lot about how well they work, and how much they cost. The three most common materials are aluminum, stainless steel, and mild steel, and all have their pros and cons.

• Aluminum is very light, so it doesn’t add much to the weight of the bike. But it’s not as strong as either kind of steel, and it’s harder to work with so it costs more. About the only real plus with aluminum is that it doesn’t rust.
• Stainless steel doesn’t rust, either, so if you live where it rains a lot, or you ride where river crossings are common, it’s a good choice. But stainless steel isn’t very flexible––you could almost say it’s brittle––and transfers more of the energy of an impact to the bike’s frame or engine than a material with some give. That brittleness makes it more susceptible to cracks at the welds caused by engine vibration, too.
• Mild steel is the best compromise, inexpensive to build, strong enough to protect the bike, and yet flexible enough to bend without breaking. Its one downside––mild steel rusts––is easily dealt with by treating the bars with a corrosion preventive before powder-coating them, such as SW-MOTECH does with its crash bars. Scrape off the surface finish down to bare metal, however, and the damaged spot will eventually rust.

Tube diameter is not a surefire indicator of how strong a crash bar is––it takes the right combination of outside diameter and wall thickness to get the highest strength and the lowest weight. For any given wall thickness a larger tube is stronger, but it exposes more surface area to potential damage, and wherever a thin wall is dented it loses strength. Some manufacturers opt for small-diameter tubing with thick walls, while others go the opposite way.

The mounting brackets that hold the crash bars to the engine or frame can’t be too thick or they’ll transfer too much impact energy straight to the mounting points. Like the crash bars themselves, they need to be strong enough to resist bending but not be unbendable.

Well-designed crash bars should protect the bike while still providing access for routine maintenance like checking and changing the oil and servicing the air cleaner, and without preventing the removal of common body panels for other jobs. And they shouldn’t increase the chances of the crash they’re meant to prevent by reducing cornering or ground clearance.

How have crash bars saved one of your rides, and how well the they fare in the fall? Let us know in the comments. Also, be sure to check out our crash bar overview video below!