Luckily, many trail-run rollovers happen in slow motion. Less inertia at lower speeds minimizes the impact on vehicle components. Still, factory "sport bars" often can't support the vehicle's weight, and their tubes deform on impact.
Serious wheelers know the value of rollover protection. Like a comprehensive insurance policy, a quality rollcage can be expensive-but is worth whatever it costs if it serves its purpose just once. For Jeeps, a custom racing-style rollcage can cost more than the vehicle is worth. This discourages the average weekend warrior from commissioning a shop to fabricate a custom tubular skeleton.
At the other end of the better-than-factory spectrum are kits that bolster the factory bars. Additional tubes either bolt or weld to the existing bars to increase structural integrity. These are the most cost-effective ways to improve rollover protection.
Replacement weld-in cage kits are a middle-ground solution. They provide better protection than systems that rely on the stock cage, and are generally more affordable than a custom endoskeleton. One example is the Full Cage Kit from Poison Spyder Customs (PSC). It consists of mounting plates, gussets, and pieces of tubing that are bent and cut in lengths that are UPS-shippable. For strength, plates are made from laser-cut 3/16-inch-thick steel. DOM tubing-1.75-inch od x 0.125-inch thick-is strong yet maintains clearances for factory tops, the dash, doors, stereo, and window cranks.
The factory cage bolts to...
The factory cage bolts to the windshield frame and to the tub behind the front seats and on the rear wheelwells. PSC recommends removing the carpet, seats, and belts so that welding spatter won't damage or ignite them, and the visors also need to be yanked. Rent a friend if necessary and lift out the factory cage to avoid having to disassemble it.
PSC recommends setting aside up to 16 hours to install one of its Full Cage Kits, which are available for Jeep CJ-7s, YJs, TJs, and LJs. The kit can conceivably be tacked together by any Jeep owner who's capable of MIG-welding a high-school-shop-worthy bead. Then the mocked-up cage can get its finish beads from a bona fide welder. (Cage strength will only be as good as its weakest weld.)
For Jeep owners who tend to go fast and potentially roll hard, the PSC cage can always be further fortified. Customizing possibilities include tying the cage to the frame (without compromising its integrity) with additional tubes and sandwiching the tub between mounting plates. Alternately, Jeep owners who also have PSC rock sliders can drill through the tub and use 3/4-inch-diameter steel sleeves to bolt the cage feet to the sliders, which in turn bolt to the OE frame/body mounts. Also, corner bends can be triangulated with additional pieces of tubing if rear-seat passenger comfort and convenient cargo-area access aren't priorities. (PSC opts for affordability by minimizing the number of parts in the kit.)
You should also wipe down...
You should also wipe down all the kit components with brake cleaner to remove oil and grease to make cleaner welds. To start the installation, bolt on the kit's windshield frame brackets with the factory hardware.
Next, bolted to the rear fenderwells...
Next, bolted to the rear fenderwells are the rear hoop plates. They're slotted for some adjustment and also use the factory Torx bolts you removed with the stock bar.
The main hoop plates replace...
The main hoop plates replace the factory floor mounts. Holes are slotted here, too, to permit maneuvering for the flushest fit.
One important note: According to Chrysler insiders, the windshield and cowl are structurally vital for rollover protection. Lowering the windshield cuts rollover resistance approximately in half.
Highlights of a PSC YJ Full Cage Kit installation are documented here. Stripping the interior and tacking the kit together took the better part of a day. Then the cage went to a qualified welder, after which it was painted before being bolted back into the YJ.
* Torx-bit set (up to T-50)
* Welder, helmet, gloves
* Ratchet straps
* Able-bodied assistant(s)
After removing the interior...
After removing the interior brackets that keep the windshield upright, secure the kit's dash supports with the factory hardware. Verify the door clearances and slide in the front floorplates before torquing down the dash support bolts.
Tack the dash uprights to...
Tack the dash uprights to their floorplates. Don't be in such a hurry that you forget to wear gloves. Next, ask a friend to hold the main side tubes while you tack their ends to the rear plates. Then switch ends and tack the front ends of these tubes to the upper windshield plates.
The behind-the-seat uprights...
The behind-the-seat uprights get tacked to the floorplates and main side tubes, and then the two vertical windshield-frame tubes go in. They connect to the dash uprights and main side tubes.
Center spreaders can be spaced...
Center spreaders can be spaced to serve as a mount for an overhead console, CB radio, or other gear. The rear tubes are coped to fit one another while allowing a little variation in positioning. Top tubes sit fairly level for top clearance and to evenly distribute the load when upside down.
Decorative gussets are another...
Decorative gussets are another functional option. The basic kit also includes a longitudinal behind-the-seats bar, which provides extra stability but can be left off if rear-seat access is a priority. A seatbelt bung kit allows the factory belts to be reused. Retaining the slider feature requires using two kits and drilling additional holes. One clearance compromise with the YJ kit is that the e-brake pedal must be bent about 45 degrees to clear the windshield upright.
Finally, verify top clearance...
Finally, verify top clearance and modify bar positions if necessary. PSC recommends that final welding be done with the cage removed from the vehicle. This also makes the cage easier to paint or powdercoat.