Channel2000.com - Will The Real Trucks Please Stand Up?

Will The Real Trucks Please Stand Up?

By Brent Romans

Fishing pole? Check. First-aid kit? Check. Toilet paper? Check. Spam? Check. I recall packing this equipment in my youth for one of my dad's involuntary camping trips into the great American wilderness. My observant mother, who refused to attend, wondered aloud, "Why spend three days sleeping in a drafty tent when there's a perfectly good bed and coffee maker at home?"

My dad told her she didn't know what she was missing. The clean air, he said. The beautiful vistas, he said. He conveniently left out the part about cleaning and gutting fish.

Back in those camping days, my dad didn't own a truck, so we were often limited in terms of where we could go. If we were to make the same trips today, I'm sure my dad would own an SUV of some sort, as they are the hip product for people with active lifestyles.

Or at least that's what TV tells me. Every truck or SUV commercial I see shows a vehicle blasting through giant snow banks, bouncing over boulders and forging rivers similar to the Mississippi, but wider and deeper. This is interesting. If truck and SUV owners are truly gallivanting about outdoors, then they certainly aren't at home watching TV sitcoms. This would mean truck and SUV commercials are missing their target audience.

Which, of course, they're not. It's no secret that most Americans like the idea of owning a rugged SUV or truck, but rarely have any intention of using it in a serious off-road fashion. Who would want to remove his or her new $35,000 vehicle from the safe confines of the mall parking lot? You would run the risk of getting dirt on the leather seats or inside the six-disc CD changer!

Vehicle manufacturers are aware of this, and many trucks and SUVs are becoming more car-like. This is fine, but it often comes at the expense of true off-highway capability. And isn't that what the whole SUV and truck image is based on?

If you are looking to purchase a new truck or SUV, and you really do intend to use your vehicle as the commercials demonstrate, there are some things you should consider. Don't blindly assume that just because it's an SUV, it will take you and your family anywhere. A vehicle's design and components have a large influence on how it performs on dedicated off-highway vehicle trails. Following is a breakdown of truck- and SUV-specific systems and how they determine a vehicle's abilities.

Four-Wheel Drive This is the critical element to any vehicle that is going to be used off-road. Most SUVs and trucks are available with either two-wheel drive or four-wheel drive. A truck without a 4WD system has the advantages of better fuel economy, less mechanical complexity and reduced curb weight. But a 2WD truck will be nothing more than a weak kitten when pitted against challenging terrain.

A truck with an engaged 4WD system will have additional traction because it applies power to all four wheels. This is very beneficial when climbing hills or driving on loose dirt, sand, or snow.

Nearly all of today's trucks and SUVs have a 4WD system of some sort. But the designs vary widely. Most beneficial to a vehicle that is venturing off-highway is a two-speed transfer case. So equipped, a 4WD vehicle has the option of being engaged in either "4-Hi" or "4-Lo." 4-Hi is normal 4WD operation. In 4-Lo, the gearing inside the transfer case changes to give the vehicle additional low-end grunt at the expense of higher speeds. With 4-Lo engaged, a vehicle is capable of climbing and descending hills that would stymie other vehicles without a two-speed transfer case.

Most 4WD pickup trucks have two-speed transfer cases, but an increasing number of SUVs do not. Many small SUVs (like Ford's new Escape and Honda's CR-V) don't have them. BMW's $50,000 X5 doesn't have one, either. Without a two-speed transfer case, a vehicle is considerably more limited in terms of what kind of terrain it can be driven on.

Ground Clearance A common complaint about trucks and SUVs is that they are hard to get in and out of, especially for people of smaller stature. The step-in height is just too high. As such, many newer trucks and SUVs often feature a reduced ride height to improve entry and exit. A lower ride height also improves handling and fuel efficiency.

The problem here is that many critical components are placed in harm's way when driving over rocky terrain. These components under the vehicle include things like the oil pan, drivetrain parts and the gas tank. If a vehicle has a low ride height, the risk of damaging parts becomes much greater. As you can imagine, punching a hole in the oil pan can really put a damper on your outdoor activities.

Most trucks and SUVs can be ordered with step bars or running boards. These accessories can help entry and exit into a vehicle that still has a high ride height. They can also improve the looks of the truck. However, since step bars hang lower to the ground than the rest of the vehicle, they are often the first items to get bashed while driving over challenging terrain. Banging up a step bar won't stop a vehicle from running, but they are expensive to replace. If you can readily get in and out of your vehicle, forgo step bars or running boards if you plan on serious off-highway duty.

Suspension Design and Wheel Travel In terms of suspension design, good performance on pavement is often contradictory to good performance off-road. In order to have the best traction possible while driving over ruts, bumps, and rocks, a truck needs a softer suspension with lots of wheel travel. The goal is to allow the tires to be as compliant to the ground as possible.

Having this kind of suspension isn't the best for on-road feel, however. The truck can feel like it's wallowing or is unstable. As such, some of the more car-like trucks and SUVs have tighter suspensions with less wheel travel. These SUVs will behave better on the pavement, but on rough trails their suspensions won't be able to keep the tires in contact with the ground as much as other vehicles.

There's also the issue of independent suspensions versus solid-axle suspensions. In off-road situations, a solid-axle suspension is more advantageous than an independent suspension. This is because as one wheel travels over a rock or bump, it tilts the whole axle up, providing additional ground clearance for that axle's differential. Additionally, solid-axle suspensions are usually stronger and more robustly built. The problem with a solid-axle suspension is that its on-road handling and ride quality suffers in comparison to an independent suspension.

If you're worried about not knowing what kind of suspension a truck or SUV has, don't worry; they all have about the same setup. Most light-duty trucks and mid- and full-size SUVs feature an independent front suspension and a solid-axle rear suspension. Most small SUVs have fully independent suspensions. Some Chrysler products like Jeeps and Dodge trucks feature a solid-axle suspension both front and rear. This is one reason why these trucks have such good reputations for off-road performance.

Limited-Slip and Locking Differentials Though rarely offered as standard equipment, a limited-slip rear differential can substantially improve off-road capabilities. Normally, if one of the rear wheels is spinning on a slippery surface, the differential will send all the power to that wheel because it's moving faster. The wheel that still has traction doesn't get any power and goes nowhere fast. The vehicle just sits there with one wheel spinning. This standard type of differential is called an open differential.

When equipped with a limited-slip differential, the amount of power directed towards the spinning wheel is reduced and redirected to the wheel with traction. In off-road situations, a limited-slip is helpful in low-traction situations like driving over sand, gravel, snow, or ice. Another advantage to a limited-slip differential is that it doesn't adversely affect the vehicle while it is being driven on pavement.

Most trucks and SUVs that have a two-speed transfer case will lock the center differential while in 4-Lo mode. It's very helpful in low traction situations as both the front and rear wheels receive the same amount of engine power. Without a locked center differential, a truck can have a traction problem with one front wheel and one rear wheel spinning on a slippery surface. The front and rear differentials feed power to the wheels without traction and won't let the gripping wheels move. A locked center differential is not recommended for pavement use, however, as it severely degrades turning abilities and increases drivetrain wear.

A handful of vehicles can be ordered with manually operated locking front or rear differentials. In locked mode, the left and rear wheels of a particular axle receive the same amount of power. If one wheel doesn't have traction, the locked differential doesn't let it spin. Full power is delivered to the wheel with traction, and the truck moves ahead. Currently, only some Toyota trucks and SUVs can be ordered with this, though "lockers" are available readily through the aftermarket.

Some high-end vehicles like the Mercedes-Benz M-Class are equipped with an electronic system that can limit wheel spin in off-road situations by using the brakes. It is similar to ABS, but in this case it is used in low-speed situations. When wheel slippage is detected, the system applies brake pressure to the wheel that is slipping, effectively doing the same job that a limited-slip or locked differential does.

Tires Some SUVs come equipped with passenger-car tires as standard equipment rather than light-truck tires. Light-truck tires are noisier while driving on pavement, but they usually are more resistant to flats and sidewall damage. They will also have tread designs that will be better suited for off-road situations.

Conclusion It makes complete sense for truck and SUV manufacturers to build vehicles that have car-like characteristics. After all, many people are using their trucks and SUVs no differently than they would a car. But as a potential buyer, you should be aware that aggressive styling and add-on brush guards do nothing for off-road capability. If you are serious about wanting a vehicle that can take you to places few others tread, do your homework about how your potential truck is designed.