Exo-Cages, Rollcages, & Building Basics
Average folks must think we're nuts when they see our rigs go whizzing by completely covered in steel tubing. Who can blame them? It takes a hard-core wheeler to really appreciate the beauty of a vehicle wrapped in steel tubing. So if you're new to wheeling and just don't get all the steel stuff, let us explain the basics of rollcages and exo-cages to you.
In the most basic of explanations, a rollcage is a protective steel frame of tubing built inside the vehicle to protect its occupants in the event of a rollover or accident. Rollcages are readily available from aftermarket manufacturers and off-road fabricators, but they will likely be called something else for liability reasons, such as sport cages or trail cages. However, even under a different name, many offer protection and safety.
There aren't too many manufacturers that sell exo-cages or kits. Exo-cages, which are built on the outside of the vehicle, are mostly one-off custom builds from specialty off-road shops. To the best of our knowledge, the only vehicles ever fitted with factory exo-cages are the Defender series built by Land Rover. Exo-cages offer some passenger safety but are generally added to a vehicle for body protection. They also work very well on tall or longer-wheelbase vehicles. The theory is that the longer the vehicle, the smaller the turning radius. The taller the vehicle, the more it will lean into obstacles, hence the need for additional body protection in tight spaces like narrow canyons.
If you are going to build or add a fully functional rollcage or exo-cage to your vehicle, you will be adding hundreds of pounds of weight and rolling resistance. A full interior rollcage with the addition of an exo-cage can add 200 to 500 pounds. Be prepared for a dramatic drop in fuel economy and performance. Also, keep in mind that the additional weight may take its toll on your suspension, requiring different spring rates, new shocks, or the revalving of your shocks.
The two types of steel used for rollcages and exo-cages are 4130 chromoly and DOM (drawn over mandrel) steel tubing. Welded-seamed tubing is not recommended. Tubing sizes will range anywhere from 1 to 2 inches. Chromoly is a high-strength alloy steel that contains chromium and molybdenum. It's a misconception that chromoly is lighter than DOM. Since it is stronger, smaller diameters of chromoly can be used. For example; 0.090-inch-wall chromoly has about the same strength as 0.120-inch-wall DOM tubing. When chromoly is welded, great care should be taken, otherwise it can become cracked and brittle. If you haven't welded chromoly before, consult a professional before attempting to build a cage that is there to potentially save your life. DOM steel tubing is a lot easier to work with than chromoly and is about half the price. A cage built with DOM tubing-properly welded, gusseted, and constructed-should be safe and strong enough for any four-wheel build. Quickly quenching chromoly or DOM steel can cause cracking and lamellar tearing. Both metals should be allowed to air-cool. Chromoly tubing thicker than 0.120-wall inch should be heat-treated after welding.
We have seen some pretty cool rollcages manufactured and custom built over the years. We like to think of a good rollcage builder as a fine artisan. Whether you are buying a cage or building your own, we highly recommend you do your research and choose wisely.