Click for Coverage
Due to the EU’s Global Data Protection Regulation, our website is currently unavailable to visitors from most European countries. We apologize for this inconvenience and encourage you to visit for the latest on new cars, car reviews and news, concept cars and auto show coverage, awards and much more.MOTORTREND.COM
  • JP Magazine
  • Dirt Sports + Off-Road
  • 4-Wheel & Off-Road
  • Four Wheeler

Built For The Rocks

Posted in How To on June 1, 2011
Share this
Photographers: Courtesy of Jeep

Here is a scenario many of us are familiar with: In front of you lies a boulder-strewn path of assured vehicular destruction. Rigs that have gone before you have been beaten into submission with broken axles, punctured oil pans, and reshaped sheetmetal. Sure, you could take the bypass, but where is the adventure in that? As a crowd of onlookers forms, you make the decision to proceed with confidence because you know that your rig has been built to survive.

If you feel this strongly about your rig, you understand what it takes to tackle extreme terrain. If you would have taken the bypass, but wanted to take the obstacle in this scenario, we’ll show you the best ways to fortify your rig so it can tackle the most impossible rocks Mother Nature can put in your path. Not only will you be able to take tougher trails, but you’ll also have more fun at the wheel.

Follow our suggestions and we’ll set you up to get high fives at the end of the obstacle that appeared impassable.

Make Some Room
When it comes to rockcrawling, clearance is your biggest ally. The whole point of lifting a truck is to fit bigger tires to be able to get the axles further away from the ground. With more clearance, you have a greater ability to drive over obstacles, keeping your important parts from interacting with the rocks and lessening the wear and tear on the machine.

The only way to create more ground clearance under a solid axle is to fit taller tires. The bigger the meats, the more clearance you’ll gain at your lowest points.

See Clearly Now
One of the best things you can do to your rig is to improve what you can see from the driver’s seat. Installing rock doors, or taking your doors off all together, are just a couple ways to improve your visibility. Enhanced visibility allows you to pick better lines, place wheels more accurately on obstacles, and more easily communicate with your spotter. As anyone who has done it before can attest, the difference between doors and no doors on the trail is just about as noticeable as the difference between auxiliary lighting or no lighting on a night run.

Project ’Con Artist can be seen here on the Rubicon with a set of Rancho Rock Gear tube doors, which allows the driver to put the wheels more precisely over the trail.

Get the Low Down
We have been following a trend of LCG, or Low Center of Gravity, for a while now. This movement has been to go with as low a lift as possible, or in some cases, no lift at all, while fitting the tallest tires possible. Keeping the center of gravity low equates to better stability on the trail and less of a chance to flop or roll on uneven terrain. Several companies have introduced LCG kits in recent years, which can include higher fender or flare positioning and new body panels. For those of you not as concerned with looks, the old standby philosophy of not fearing the Sawzall is still alive and well. A little fender trimming goes a long way. Another trick to lowering your center of gravity is to fabricate an attachment point to your axle so that the winch can pull the body closer to the axle for those maneuvers that put a priority on stability over suspension travel.

Vehicles such as Jeep’s Lower Forty use stock springs and raised bodywork to fit 40-inch tires—the best of both worlds.

Real 4WD
Unless you have lockers in your front and rear differentials, you don’t have a true 4x4, no matter what the sticker on the bed says. Most 4x4s come from the factory with open diffs and two-wheel drivethat is, only one wheel per axle turns (the one with the least resistance), potentially leaving you stranded. Lockers are essential in the rocks and come in many forms, from Lincoln Lockers to spools. The most popular lockers today are selectable units because they allow the driver to engage them only when needed, but automatic units such as the venerable Detroit Locker are still stalwarts in the sport.

Selectable lockers, such as this ARB Air Locker, are especially useful in front differentials where the locker can be disengaged when turning on tight trails and reengaged at the press of a button.

Bead Security
Beadlocked wheels allow the tire to be run at extremely low pressures without the worry of it coming off of the rim. Non-beadlocked wheels are usually only safe to run to about 12 psi, while beadlock-equipped wheels can support tires that are aired down to little or no air, depending on the tire. The difference in psi from 12 to 5 is significant when traction is hard to come by. Another thing to look for when outfitting your rig for rocks is a wheel that protects the valve stem from being ripped open on the trail. Yeah, we’ve seen that happen.

One of the more popular beadlocks currently on the market is the Raceline Monster, seen here at the 2011 King of the Hammers race.

Slow Roller
Low gearing is the key to total control on the trail, as it allows the vehicle to crawl over obstacles and makes the most out of the torque available at low engine rpm. Low gears slow down the action, making it easier for the driver to decide on the fly about his line. At slower speeds, weight transfer is more predictable and wear and tear is minimized. Keep in mind that if your rig is used in mixed wheeling, it is important to choose your gearing wisely, as there is such a thing as going too low. The OE industry seems to have settled on 4.0:1 low-low gearing, which is what Hummer offered in its H3 Alpha and Jeep offers in its JK Rubicon. However, aftermarket transfer cases such as Advance Adapters’ Rubicrawler and Atlas 4 and Stak’s three-speed Monster Box offer multiple low gearing options to make your rig as flexible as possible.

The Rubicrawler is one method of achieving more than one low range gear ratio. Having more than just a single low-range gear ratio can be beneficial for rigs that are used in varied terrains.

Up Your Shaft Size
With low gears and locked-up axles, much more stress is being routed through your drivetrain. Usually this stress shows up as broken or twisted axleshafts. Thicker shafts of stronger material are a great upgrade to any 4x4 and should be done at the same time a new differential is installed to save on labor. Other options include upsizing complete axle assembliesgoing from a Dana 44 to a Dana 60, for example. In addition to being able to better put up with drivetrain stress, stronger axles resist bending or twisting when the going gets rough. Nothing can ruin your day quicker than a busted shaft in a precarious spot on the trail.

Thicker axleshafts are an important upgrade to any 4x4. Here you can see the difference between a Dana 44 (bottom) and a Dana 60 (top).

Judge Tread
If you want to hit the rocks, you’ll need a tire that is built for abuse. Things to looks for in a tire are a durable, pliable carcass and big sidewall lugs to widen the contact patch. In this venue, bias-ply tires are king, although radials can hold their own. Also important to the equation is tread compound. The stickier the rubber, the deeper you can get into challenging terrain. Also look for a tire that has good biting edges, like those seen on the bias-ply Pit Bull Rockers or the bias-belted Mickey Thompson TTC Claws.

The bias-belted Mickey Thompson TTC Claw is ideal for jagged rocks. Note the massive sidewall lugs that essentially widen the contact patch when the tire is aired down.

Plan B
When all else fails, you need to be equipped for recovery. Sometimes no amount of planning can get you over a rock that just doesn’t want to let you go. In this case, it is best to be outfitted with solid recovery points, such as D-rings, shackles, hooks or a receiver hitch, along with a winch and a bag full of the essentials. Recovery bags should include tree savers, straps, winch-line weight, gloves, and a snatch block.

Wire rope still holds an advantage over synthetic line in the rocks because of its resistance to fraying, but synthetics can be used successfully if a rock guard is used and the operator is careful.

Armor All
Nothing can ruin your day like a hole in your transmission pan or a fuel tank that used to hold 20 gallons but now only holds 15. Skidplates not only protect your vitals, but good ones with countersunk hardware will allow your belly to glide smoothly over obstacleseven when you have run out of ground clearance. Not only should skidplates protect, but they should also be able to support the weight of the vehicle. The same goes for rock sliders, which should be sturdy enough to pivot off of, or support, the rig during a tire change.

While Project ’Con Artist may look stuck in this photo, it isn’t. Thanks to strong skidplates that could hold the weight of the vehicle and a smooth underbelly, we were able to rock the Jeep back and forth to free ourselves from the grip of the Rubicon.

Armor comes in many other forms, such as shock mount protection, rock sliders, and bumpers. For those of us who use our daily drivers to the limits, bumpers, rock rails, and panel armor keep the body straight.

Hydro Lock-to-Lock
When deep in the rocks, it is fairly easy for a traditional steering system to get bound up or fail under the stress of big tires and high resistance. To alleviate the problem and make navigating boulders easier, a more powerful hydraulic steering system is often fitted. Hydraulic assist adds a ram to help the stock system, while a full hydraulic system eliminates the steering box, pitman arm, and draglink altogether. Because full hydraulic systems remove the mechanical steering linkage, they are more compact and can allow increased suspension travel. However, full hydro is suitable for trail rigs only. FW

On this TTC rig, the hydraulic steering ram is clearly visible and needed to navigate through the Tank Trap.

Connect With Us

Newsletter Sign Up

Subscribe to the Magazine

Browse Articles By Vehicle

See Results