What is a bull bar?
The term "bull bar" is a South African colloquial descriptor for a device mounted to the front of a workhorse double cab. Originating from Australia, these devices were fashioned from heavy gauge steel and welded to the front of farmers' UTEs. They were originally called "roo bars" or "dongs" due to their sound when they struck a Kangaroo. Less about styling, the bull bar was necessary for rural farmers worldwide to protect the vehicle and driver from impacts with cattle and wildlife.
Later, these became a styling addition used by 4x4 enthusiasts, who saw them as a way of protecting the grill and headlights of their off-road rigs from rocks, trees, and other obstacles encountered off-road.
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Today, in suburban settings, it is safer to call these "nudge bars" as they are made from light gauge steel and very often not welded to the chassis. They are essentially for light duty only and, in most cases, are purely an aesthetic add-on for most SUVs and double cabs. These styling add-ons will do little to protect you or your vehicle if you encounter a wild animal at speed in the dead of night.
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Should you fit one?
Whether you will herd cattle or pretend that you may one day, sure, go ahead! Most manufacturers will have approved fitment centres that have specifically developed the nudge bar for the vehicle in question. There is a caveat, though, that is to only fit approved aftermarket units covered by the manufacturer's warranty, as fitting ones that aren't could lead to your warranty being cancelled.
Also, know what you are buying and what the bar can and can't do. Never use the bar as a recovery point off-road, and for goodness sake, please do around ramming cows or cacti!
Like so many other things in life, style is subjective, so if you feel your family SUV needs one, go ahead.