Crossovers have become so commonplace as suburban accessories these days that it's easy to forget that they do have off-road capabilities. Or should. With that in mind, we gave our Four Seasons Acura ZDX, Audi Q5, and Subaru Outback a break from their grocery runs and slung them through an off-road-vehicle route in northern Michigan. Our intent was not to conduct a torture test in which the winner would be the one that didn't need to be winched out, but rather to have an all-wheel-drive adventure that any crossover owner should be able to make without risking life and tailpipe. That said, we weren't sure at the outset of our journey if all three vehicles-on stock tires inflated to normal pressures-would come through with fenders and dignity intact.
The ride started simply enough, with a slow climb up a narrow trail. Senior web editor Phil Floraday, the off-road expert of the group, wryly advised us to use "as little power as possible but as much as is necessary." Easier said than done, especially in the Outback, which has a difficult-to-modulate throttle.
The first true challenge arrived about fifteen minutes in, when the three crossovers met a murky puddle. After Floraday deemed it fordable, the three vehicles waded through one by one. No problem for the Q5, which kept its mouth above the water. The Outback wasn't quite as comfortable. At the deepest point, water splashed up onto its hood, and the boxer engine sputtered briefly before the car chugged its way out of the muck. Clearly unhappy, the Subie belched some vile-smelling steam through its grille and flicked on a check-engine light that we can only assume means, "Don't drive me through any more deep puddles, you idiot." It was the low-slung Acura, though, that made us the most nervous. Enough water sloshed into its engine bay to momentarily cut power. It fought through and emerged with no assistance, but the air-conditioning blew hot air for the rest of the day.
The ZDX would regain a measure of confidence during our next obstacle-deep sand. Blessed with sophisticated torque-vectoring all-wheel drive and defeatable traction control, it practically danced through the soft terrain, kicking up a rooster tail of sand in its wake. After the sand was churned and loosened, the Q5 and the Outback had more trouble, mostly because the electronic nannies insisted on intervening even when we tried to disable them, cutting momentum and the wheel spin needed to keep the treads clean.
Our final hurdle was the most threatening: a steep slope covered in the same deep, soft sand and pitted with ruts and drop-offs large enough to thoroughly trap any of the three vehicles. We were growing weary of the squealing pebble caught under its front brake caliper, but the Q5 was still going strong, making it up the hill on the first try. The Subaru seemed to be doing fine as well until a slight steering error by our least experienced off-roader-me-sent it into one of the drop-offs. (Note: when your spotters cry, "No! No! Stop!" heed their advice.) With some careful reversing and a push from road test coordinator Mike Ofiara, the Outback was freed. A second assault-with a new driver-made the route look easy. The ZDX made it up on its first attempt, but after we reran the climb and marred the trail, the Acura struggled the most. The heaviest of the group at nearly 4500 pounds -- about a half ton more than the Outback -- it needed a running start and a firm foot on the throttle to conquer the sandy step at the top.
All of this may sound excessive, but our trio of crossovers did everything we asked of them, and none required more than a thorough cleaning before reporting back for daily duty (the Q5's pebble popped out, the Outback's check-engine light cleared, and the Acura's air-conditioning returned, all on their own accord). We also have greater appreciation for how and why these vehicles differ from more carlike offerings. We better understand why someone might pick a high-riding Q5 over an A4 Avant. The Subaru's soft ride, a constant complaint among editors, was a godsend for the way it damped the constant crashing of the rough trail. And the Acura...well, it still doesn't make all that much sense to us, but it performed bravely for being so clearly out of its element. It also might look a bit better when covered in mud. Most important, we can now confirm that any one of these vehicles is capable of soft-road heroics with no modifications -- but do try to stay out of deep puddles.
Techtonics: All-Wheel Drive
Acura uses two clutches in the rear differential to manage the front-to-rear torque bias. Each clutch, controlled by an electromagnetic coil, is responsible for sending torque to one of the rear wheels. With an electronically controlled system, the vehicle has to detect slip and actuate the clutches before torque is rerouted. It's a slower response than Audi's purely mechanical system, but with modern sensors and control systems, you won't exactly catch the Acura napping. Plus, the ZDX can vary torque between the left and right rear wheels better than any other vehicle here.
Audi's Quattro all-wheel drive is based on a torque-sensing center differential, with the bias controlled by two sets of planetary gears and several friction discs. The system's weakness is the open differentials on the front and rear axles. To prevent the Q5 from spinning its wheels helplessly, Audi doesn't allow stability control to be switched off. Instead, an "off-road" mode that lowers the intervention threshold is engaged. To keep the Q5 moving forward if a wheel has no grip, the system applies the brake on that wheel to direct torque to the opposite side.
So-called Symmetrical All-Wheel Drive isn't necessarily symmetrical, as Subaru now has four all-wheel-drive systems, and only one has a base condition with a 50/50 split. Our Outback's arrangement typically sends 55 percent of torque to the rear wheels. Torque is divvied up by a compound planetary gearset; when slip is detected, an electronically controlled clutch increases or reduces the friction between the two ring gears to change the front-to-rear distribution. A viscous limited-slip rear differential reacts to differences in wheel speed. The front axle uses an open differential. - Eric Tingwall
Acura ZDX SH-AWD
Engine: 3.7L V-6, 300 hp, 270 lb-ft
Ground clearance: 7.9 in
Wheelbase: 108.3 in
Normal torque split, f/r: 60/40%
Max torque split, f/r: 90/10 to 30/70%
Engine: 3.2L V-6, 270 hp, 243 lb-ft
Ground clearance: 7.9 in
Wheelbase: 110.5 in
Normal torque split, f/r: 40/60%
Max torque split, f/r: 65/35 to 15/85%
Subaru Outback 3.6R
Engine: 3.6L flat-6, 256 hp, 247 lb-ft
Ground clearance: 8.7 in
Wheelbase: 107.9 in
Normal torque split, f/r: 45/55%
Max torque split, f/r: n/a