Suspension of disbelief

By DAN NEIL

Jan. 14, 2004 12 AM PT

Trying to tell BMW how to tune a suspension is like telling Savion Glover how to tap-dance or telling John Ashcroft how to be scary. But when it comes to the new BMW X3 compact sport ute ... wait, there’s a helicopter over my house.

Look, I’m just a humble shade-tree mechanic, unschooled in computer-modeled suspension kinematics, but I know when my fillings are coming loose. The 2004 compact ute X3 rides like an old door being dragged down a dirt road.

Our test model -- the X3 3.0i with sport-calibrated suspension (I use the term “calibrated” advisedly) and 45-series Dunlop tires -- spazzed and trembled at the slightest imperfection in the pavement and was sent into palsied fits by the 10 Freeway. And the impacts sent through the seats by speed bumps felt like the unwanted attentions of an amorous moose.

BMW calls the X3 an SAV, which stands for “sport activity vehicle.” That activity is going to your chiropractor.

The main culprit is the sport suspension and, in particular, the low- profile performance tires. To be fair, the X3 is fantastically agile on asphalt, with truly ludicrous amounts of lateral grip, knife-edged responses and heroic brakes. I, for one, think those are wonderful things. I get misty at the mere mention of lateral grip.

It’s also quite quick. Our six-speed, 3-liter tester accelerated like a middle-school kid with a snoot full of Ritalin: zero to 60 in about 7.4 seconds. Triple-digit cruising is dangerously easy.

But you can only go hellbent-for-leather once in a great while, whereas the X3’s thrumming, tympanic ride is with you every minute you are in the car. Like tinnitus.

It only goes to prove that it’s hard to make a sport ute -- even a little one -- the ultimate driving machine.

Let’s lay a little groundwork, shall we?

A car’s suspension carries the weight of the car to the wheels, typically through four coil springs, one on each corner of the car. The springs absorb the kinetic energy from bumps in the road, and the shock absorbers or struts stabilize the car body by dissipating the spring energy so that the car body doesn’t flop around as if it were atop four Slinkies. The suspension members -- like the familiar “wishbone” or A-shaped unit that is pretty easy to visualize -- are there to keep the wheels in position and as nearly upright as possible as the car maneuvers.

There are millions of variations on this theme -- MacPherson struts, leaf springs, torsion bars, short-long arm, trailing links -- but the idea is to allow the tires to follow the contours of the road while the car body goes along undisturbed and, when the vehicle maneuvers, to ensure that body motions are controlled.

The problem with SUVs is that they have high centers of gravity; in other words, they are top-heavy. The greater the vertical distance between the center of gravity and each axle’s roll center -- the imaginary point around which the vehicle body rotates, or “rolls,” when cornering -- the more body roll the vehicle will exhibit. This distance is called roll-couple; anyone who has ever overloaded a wheelbarrow only to have it tip over understands the concept.

The X3 rides on a slightly stretched and widened version of the BMW 3-Series platform. The suspension is nearly identical: upfront, MacPherson struts (units comprising a coil spring around a hydraulic damper); and in the rear, multiple suspension links, including a large alloy upper link carrying the spring. Big antiroll bars lace both sets of wheels together. All things being equal, the X3 should have something of the 3-Series’ wonderful balance between performance handling and compliant ride.

But all things are not equal. The X3 is almost 10 inches taller than a 330xi sedan (with all-wheel drive) and weighs 540 pounds more. To control all this extra weight swinging aloft in the rigging, BMW’s chassis gurus were obliged to put the most aggressive set of springs, shocks, antiroll bars and tires they could countenance on the X3.

The result: forbidden moose love.

In a way, I find BMW’s unwillingness to compromise on performance admirable. Like Porsche -- which betrayed its long-standing sports car ethos to build the moneymaking Cayenne SUV -- BMW entered the SUV market (with the X5 in 2000) not out of any great love for the category but because it was a cash cow that Munich desperately needed to milk. The X5 has sold like Bavarian strudel, about 38,000 in North America last year, and is in many ways the template for a whole generation of street-tuned SUVs such as the Infiniti FX35/45 and the Volvo XC90.

The X3 comes in two flavors: the 2.5i with the 2.5-liter, 184-horsepower straight-6; and the 3.0i with 3 liters and 225 horsepower. Both of these free- revving, hard-pulling engines are found in the 3-Series, and both can be paired with the five-speed Steptronic automatic and six-speed manual transmissions.

The X3 2.5i, with a base price of $30,300, is a timely and expedient niche filler for BMW. It is priced about $6,000 below the X5 3.0i, even though it is only marginally smaller. The X3 is considerably more space-efficient than the X5. The new model also amortizes the cost of much of the design and tooling for the 3-Series.

BMW was so keen to get the X3 to market that it farmed out the assembly to the Magna Steyr company in Graz, Austria, which will produce a whopping 75,000 vehicles annually.

I predict the world’s consumption of BenGay will skyrocket.

Anybody who takes the X3 for a flog up a canyon road will notice the car’s crisp turn-in characteristics -- which is to say, as you steer into the corner, the front tires bite and the X3 tracks right where it’s pointed. And should you exceed the front tires’ substantial mechanical grip -- if the car is understeering -- the X3’s new xDrive will lend a hand.

This full-time AWD system uses an electronically modulated multi-plate differential to shift power forward and aft depending on the amount of wheel slip the digital brains detect. Under normal conditions, the torque is split 40-60, front-rear. But as you go sailing into a corner and the front wheels begin to slide, the system reduces torque being sent to the front wheels, so their available grip can be devoted to turning instead of propelling the vehicle.

My only complaint is the halfbeat it takes for the system to cogitate. I found myself making mid-corner steering corrections as the front tires suddenly gained extra purchase. In fact, the sport-endowed X3’s stuttering ride means you have to constantly tend the tiller lest you hop and skitter off course.

The xDrive system, like Audi’s Quattro system, is designed to give the vehicle more of an all-weather profile. Combined with BMW’s highly evolved cybernetics -- stability, traction, anti-lock, and electronic brake force distribution systems, as well as a new hill-descent control feature -- the xDrive offers substantial assurance that the vehicle will stay on the road.

But beware of over- confidence as you bash up toward the ski slopes. The limiting factor is the 18-inch Dunlop gumball tires. These tires stick to dry pavement like a morals charge sticks to a politician but are highly suspect on ice and snow. And off-road? Well, I didn’t hazard to take the X3 into the backcountry; however, given the limited wheel articulation, due in part to the big antiroll bars, I reckon the X3 won’t be doing the Rubicon Trail anytime soon.

And, frankly, I’m not crazy about the car’s styling, either. The nose looks long and droopy. BMWs should have taut, close-coupled fronts with short overhangs wrapped around the front wheels. The wheels look tragically tiny, like stunted limbs. Taken at a glance, the X3 looks gutless and neutered.

In the bizarre, want- it-both-ways world of sport-tuned SUVs, I still consider the Infiniti FX35/45 the best offering on the market. But with Los Angeles being the land of propeller- heads, I’m sure many BMW partisans will eagerly line up for the X3.

Their chiropractors will thank them for it.

Times automotive critic Dan Neil can be reached at dan.neil@latimes.com.

(BEGIN TEXT OF INFOBOX)

2004 BMW X3 3.0i

Wheelbase: 110.1 inches

Length: 179.7 inches

Height: 66 inches

Curb weight: 4,023 pounds

Powertrain: 3.0-liter dual-overhead-cam inline-6 engine with variable-valve timing; six-speed manual transmission; all-wheel drive

Horsepower: 225 at 5,900 rpm

Torque: 214 pound-feet at 3,500 rpm

Acceleration: Zero to 60 mph in 7.4 seconds