Just How Slick Is Slickrock?
Slickrock is actually sandstone, and it's one of the best surfaces for traction you can find off-road. The term slickrock derives from its smooth surface and rolling curves. Over the course of centuries, ancient sand has been compressed into stone with a surface texture similar to 100- to 120-grit sandpaper. What could offer better traction than that? You'll quickly find that you'll be able to drive on steeper hills than would be possible on almost any other surface.
This will hold true right up until the moment slickrock gets wet. Water is a great lubricant, and once it hits Moab's beautiful red rock, it does a great job of greasing your wheels. So, when it rains, use caution and stay off the steep slopes. Rain and snow will not only greatly reduce traction, but will also wash all the loose dirt and sand off the face of the slickrock. When driving after it rains, even weeks after in some cases, watch the terrain ahead of you. Try to avoid the pools of water and mud. If the trail forces you to get your tires wet, remember to drive a while and dry your tires before attempting anything steep.
All-Terrains Or Mud-Terrains?
The simple answer to this question lies in the fact that on slickrock, the keys to traction are more rubber and softer compounds. All things being equal, a softer tire will grip better than a hard one. The same is true when comparing the treads on mud-terrain and all-terrain tires. All-terrain tires put more rubber in contact with the slickrock. While the massive lugs of a mud-terrain are a big plus in mud and can even claw their way over sharp rocks, the thick tread blocks don't flex as much on slickrock as the smaller tread blocks of an all-terrain tire, and as a result, can slip more easily.
How Low Should You Go?
For most rigs coming to Moab, tire pressure should fall somewhere in the 16- to 18-pound range. This will provide plenty of sidewall flex and should keep the tires seated on the beads. With bead-lock wheels, of course, you can run your tires at pressures as low as 8 pounds. Naturally, these pressures are only recommendations, and your actual needs will depend on your vehicle's weight, the type of trail you're going to be running, and your driving style. Weight is an important factor when airing down because heavy rigs require more tire pressure than light ones.
Another consideration when airing down is your tire's sidewall aspect ratio. A 37-inch tire on a 15-inch wheel has more sidewall than one on a 17-inch wheel. The greater amount of sidewall provides more flex and wobble, especially at lower pressures. Also, a tall sidewall has more leverage to pop the bead than a short one. If you have tall tires on small-diameter wheels, you'll want to run higher tire pressures.