A Rear Bar is almost the reverse of a Bull Bar, in that they are primarily designed to protect the rear end of the vehicle. However, they are also very handy for doing other things. You can buy the best quality 200 series rear bar online.
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These bolts straight to the chassis in a variety of locations. This implies they're a lot more powerful than the standard tow hitch configuration. This means the weight is well distributed when towing heavy loads, and the bar is equally as robust as the chassis.
A rear bar is used primarily when you are exiting out of something when four-wheel driving. If the rear of the car is going to touch the ground, a good bar will hit it first. What this means is that you rub a bit of paint off the bottom of your bar, instead of denting and scratching your valuable panel work.
These can be designed to protect important car components as well, like fuel tanks and water tanks which are easily damaged. Rear Bars are used for mounting tires and fuel tanks as well.
You can't mount two wheels on the back of a normal car without a rear bar and tire carrier system. Some people convert the tire carriers into Jerry can holders, and add work lights and more.
A rear bar has its own lights in it too, as you will find that once you start mounting tires on them the original lights get covered over, making it unsafe to use them anymore.