A bull bar is a great accessory if you’re into off-roading. It mainly protects your car's parts in the event of a collision with a large animal, especially the radiator. Bull bars are also required to mount auxiliary lights and winches.
A bull bar allows you to drive off with a functional vehicle. Photo
Also called the kangaroo bar, it protects plastic bits like the bumper from snapping, and protects the headlights covers breaking. Basically, improving the crash worthiness of your car.
However, installing a bull bar on your 4x4 does require some research. You can’t simply Mad Max your way to installing one. Bull bars are usually mounted on the ladder frame, and since they become the first point of contact in a collision, they will affect how your airbags behave.
The first thing we need to know about airbags is that they are controlled by the ACU (Airbag Control Unit).
The ACU works by detecting impulsive force through the airbag sensor (an oversimplification is the sudden change/loss in velocity). In an impact, the airbag sensor will close its electrical circuit and cause the airbags to deploy.
A swing of the cam completes the electrical circuit on the airbag sensor and cause the airbag to deploy. Photo: speedkar99
By default, your 4x4’s first point of contact in a collision is the bumper. The bumper and the front-end panels are soft and absorb a certain amount of impulsive force.
By default, the first point of contact in a collision is the plastic bumper, a soft bumper absorbs some of the impulsive force.
A bull bar, on the other hand is usually made of rigid steel, which does not absorb the impulsive force as well. What this means is that a lower speed crash with a bull bar could produce the same impulsive force as a higher speed crash without a bull bar.
Your airbags could deploy prematurely in low-speed crashes. And prematurely deployed airbags can be dangerous.
Airbags are meant to work at a certain speed and collision scenario only. They could also cause "airbag burns"
However, not all bull bars are the same. Some are made with the least bit of research, while some are made with in depth consideration of the working mechanism of your car’s ACU.
Bull bars need to be crash tested to ensure they crumple the way they should.
You’d have to do a little bit of window shopping before deciding on a purchase.
Bull bars need to crumple to absorb the impact in a collision. Photo
Bull bars and manufacturer warranty
A pendulum crash test for bull bars. Photo: 4WD 24-7
Good bull bars will absorb the impact as your stock car would and allow the airbags to function as they should.
Although there are accreditation systems for bull bars (e.g., ADR in Australia), installing one on your 4x4 would usually void the car manufacturer's warranty.
Not that it’s a big problem, but something you should take note of.
Consult the manufacturer if you're concerned about the warranty. Taken from the owner manual of a Toyota Land Cruiser.
Matters on installation of a bull bar are usually stated in the owner's manual.
A bull bar can cause some systems in your car to malfunction. e.g. the LDA system of a Toyota Land Cruiser.
Proper installation of bull bar
Bull bars also have to be installed properly to allow for maximum absorption of impact. For example, when mounting the bull bar, make sure to install it at the furthest point possible on the bolt slot.
Bull bars need to be installed at the furthest point possible on the bracket to allow for impact absorption.
In the event of impact, the bull bar has room to move and absorb the impact.
What else should I consider if I want to install a bull bar on my car?
Air flow and tolerance. Before you buy a bull bar, make sure the design does not obstruct the original airflow pattern to cool the engine bay. Obstructed airflow can cause your engine to overheat – not something you’d want to happen on your 4x4.
Not a 4x4, but you get the point. Air needs to flow well to keep the things cool.
You also have to consider tolerance since the bull bar is hard-mounted onto the ladder frame and not the “body” on a body-on-frame car.
It is common for the body to wobble on the ladder frame. If you have a bull bar installed, it could rub against the precious paintwork and cause dents.
Uneven surfaces can cause the body and bull bar to rub against each other, provided there is not enough tolerance.
Conclusion
If your work or travelling conditions require a bull bar, go ahead and get one. But just like other products, get one of good quality. It’s great for improving the crash worthiness of your car, since it especially protects your radiator from being dislodged in a collision.
Previously an engineer in an automotive manufacturing company and a highway concessionaire. A part-time research student on biofuels and diesel engines. Obsessed with vehicle electrification and the future of transportation.
