Introduction to rocker panel protection
Savvy off-roaders don't go off road without skid plates and tow hooks, and Grand Cherokee off-roaders soon realize that their rocker panels need extra protection too. With the stock diameter tires and a 105 inch wheelbase, the breakover angle is a dismal 17.0 degrees according to the Jeep sales brochure, which really puts your rocker panels at risk.
Lifting your rig improves breakover angle and encourages you to tackle bigger obstacles, putting you rocker panels right back at risk. So the answer to the rocker panel protection problem is skid plates, commonly known as rock rails. Since Jeep does not offer rocker panel skid plates, you have to look to the aftermarket. There are some Nerf bars that are sturdily built and offer protection at some sacrifice to clearance due to large diameter tubes. Forget about Step Nerfs, they are not skid plates. This review is on Don-A-Vee Jeep's offering, the ROK Guard (part # rok2). These are made of heavy walled flat tube that tuck up against the bottom of the rocker panel and mount to the frame with 3/8" to 1/4" brackets, hardware included. They are so low profile that you have to look twice to see them.
One consideration unique to the Grand Cherokee is the Uni body construction. This lack of a separate frame limits mounting options. While the body "portion" is used in some rocker panel protection designs, attachment requires as many as 30 rivets or nut/bolt sets and is still not much stronger than the sheet metal. I bought the Rok Guard from Don A Vee for its low profile, frame- mount design. The parts I received both had slightly misaligned brackets. I doubt production tolerances on the Jeep are to blame. My resolution was to re-drill the holes to bring them into alignment with existing holes on the vehicle's exposed frame.
The front mounting point uses the same holes as the transfer case cross brace and stock bolts.
The rear mounting point is the bracket that holds the lower control arms. This spot didn't look sturdy enough, so I fabricated simple backing plates, large washers might do, for added support on the rear mounts. As usual, for me, what should have been a two-hour installation ended up as an 8-hour re-engineer and fabrication exercise, then the 2-hour installation.
The one-year analysis is that the product has held up well, and in doing its intended job, has paid for itself. There are a couple of side benefits as well. The first is that it provides suitable jack points for the Hi-Lift jack. This has come in handy when trying to re- install sway bar disconnect pins on uneven ground. Also, I effectively lowered the transfer case 1/4" by putting the forward mounting flange against the frame and the transfer case cross member under that, which also reduced some drive line noise caused by the 3.5" lift kit. Priced under $200, the ROK2 is a practical solution to one of the ZJ's shortcomings.