Less than 5, but not by much: BMW's latest SUV borrows many of its underpinnings from the 3 Series, but comes close to the X5 in most dimensions.

The young, upscale buyers BMW is banking on to buy the new X3 are unlikely to ever engage in serious off road adventures. No dummies, they'll realize it's based on the 3 Series, albeit a heavily modified 3 Series floorpan and structure. Which means this SUV--or SAV (Sports Activity Vehicle) as BMW calls it--is a crossover, and people who buy car-based SUVs are less likely to take their vehicle way off road--if they can help it. If they can't, the helpful Bavarian engineers have done their best to keep untoward experiences to a minimum by equipping their crossover with a clever drive system that keeps a firm grip on the road wherever it can.

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xDrive

Those toga-clad angels in the BMW commercials have nothing to do with how xDrive really works. In the real world, inputs from the dynamic stability control (DSC) system--each wheel's rotational speed, steering angle, the vehicle's yaw and acceleration rates, and whether the brake light switch is activated--are fed into an electronic controller. If slip is detected, an electric servo motor exerts pressure on the multi-plate clutch inside the transfer case to transfer torque to the front wheels. This unit, claims BMW, not only acts more quickly and positively than a viscous-clutch, but makes it possible to use the unit in more situations because the clutch pack can be fully open, fully engaged, or at any level in-between.

Under normal driving conditions, the driving torque split is 40% front/60% rear. With full traction at each axle, the maximum torque each can achieve is 50%, though this can shift within 100 milliseconds to 100% at one axle if its opposite is on an extremely slippery surface, like glare ice. The xDrive system is calibrated to quell understeer or oversteer as well by sending torque to the rear or front wheels, respectively; its application greatly reduces the intervention of the stability control system, which applies individual wheel brakes and reduces engine torque to keep the vehicle headed in the intended direction. (The X3's DSC system also has an added function designed to keep an errant trailer in line.) Compared to the all-wheel-drive system found on BMW's 3 Series, xDrive is nearly transparent.

Size Matters

Though it's apparent when the X3 and X5 are parked together that each appeals to a different customer (the X3 buyer is younger in spirit, if not years), a quick comparison of dimensions tells an interesting story:

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In many ways, these vehicles are nearly interchangeable, though the X5 feels and looks considerably larger, and offers a V8 engine option. Base prices for the X3 line start with the $30,995 X3 2.5i and jump to the X3 3.0i at $36,995. However, a fully loaded version of the top model will set you back an eye watering $49,520. BMW expects most heavily optioned models to cost about $42,000.

Under the Skin

Buyers have a choice of 24-valve, aluminum inline six cylinder engines, both based on BMW's M54 architecture and sporting variable intake and exhaust valve timing and a duel-resonance intake. The 2.5-liter puts out 184 hp @ 6,000 rpm and 175 lb-ft of torque @ 3,500 rpm, while the 3.0-liter produces 225 hp @ 5,900 rpm and 214 lb-ft of torque @ 3,500 rpm. Both are mated to a standard six-speed ZF Type H-6 manual, or optional five-speed Steptronic automatic transmission. Just don't expect to win any drag races with the 2.5 engine. It's pulling around 4,001 lb., and the automatic-equipped version takes a leisurely 9.3 seconds to go from 0-60 mph.

The front suspension is a new version of the double-pivot strut layout found on the X5, and 5- and 7 Series sedans, with aluminum forward lower links to reduce unsprung weight. In the back sits a multi-link design similar to that found on the 3 Series, suitably reinforced and with aluminum upper transverse links. To strengthen the areas where the subframes attach, BMW engineers added a large thrust plate in front (it also serves as a skid plate), and dual diagonal braces in the rear.

Engine-speed variable-assist power rack and pinion steering is standard, with vehicle-speed variable-assist available as an option. The brakes are 12.8-in. discs in front, 12.6-in. in the rear, and tire sizes range from 235/55R-17 to the Sport Package's 235/50R-18s. The X3 3.0i has an additional option that fits V-rated 235/50R-18s up front and 255/45R-18s in the rear, and deletes the speed limiter, which allows the manual-equipped version to reach a top speed of 139 mph.

                               X3 3.0i      X5 3.0I

Wheelbase (in.)                  110.1        111.0
Length (in.)                     179.7        183.7
Width (in.)                       73.0         73.7
Height (in.)                      66.0         67.5
Curb weight (lb.)              4,023        4,652
Interior volume (ft.[.sup.3])     96.1         97.6
Cargo volume (ft.[.sup.3])        71.0         69.0

By Christopher A. Sawyer, Executive Editor