The E39 all-steel body acts as a safety cage for occupant protection. The structural rigidity of the monocoque was increased using computer-aided engineering. This allows key points to be reinforced, to increase rigidity, without significantly adding to the weight. The overall increase is 10 kilograms (20 lb), which is offset by the aluminium suspension. Laser welding techniques ensure rigid bonding throughout. Another area of focus in the design of the body was in structural dynamics. The body was designed so that the frequencies for torsional twisting and bending are in separate ranges and above natural frequency. These frequencies are out of the range of engine and driveline vibrations; thus they will not amplify them.
The aerodynamically designed body and features of the E39 gave the 528i and 540i, 0.28 and 0.31 drag coefficients respectively. Torsional rigidity was also increased over the E34, by 40 percent. The chassis was so stiff that the rigidity was unchanged for the E60 model. This added stiffness allows the suspension to work with more accuracy. It also allows total engineering of ride quality through the suspension; rather than in combination with body flex.
Steering and suspension
Interior showcasing the updated E39′s centre console layout, with optional navigation screen.
With the E39, two steering types and double pivot, MacPherson strut suspensions systems are used. For the 520i–530i models, BMW, for the first time in a 5 series, utilised rack and pinion steering. This not only offers weight reductions over the recirculating ball type used on the V8s, but also provides quick steering response through its variable ratio. This system steers from the front of the axle.
Six-cylinder models also receive an aluminium front subframe. The struts use aluminium “Tension Link” that comes from a forward position back to the front of the wheel and an aluminium horizontal link to locate them. Aluminium is used for the: steering knuckles, outer strut tube, and the spring pads; saving 21 kilograms (46 lb).
With the 540i, BMW retained the front steering and suspension from the previous E34 540i with the design based on the E38 7 Series. The physical size, dimensions, and weight of the V8 540i required that the steering be the older recirculating ball type. This system steers from the back side of the axle. The front subframe is steel. To compensate for the heavier front end, BMW used extra aluminium in components including the steering box, steering knuckles, outer strut tube, and the spring pads. The struts are located by an aluminium “Thrust Link” that comes from the rear to meet the back of the wheel and an aluminium horizontal link.
The E39 employs similar design to the E38 7 Series for the rear suspension, regardless of the model specified. This “four-link integral rear suspension” or “Z-link” axle was first introduced on the BMW Z1. With this, Chapman struts are utilised. Through precise toe angle changes, stable yet responsive handling without unwanted toe change effects under load is achieved.
Various engine sizes and configurations have been available. The North American market saw the 525i, 528i, 530i, 540i and M5. The European range was however, more diverse, with BMW offering the 520i, 523i, 528i, 530i, 535i, 540i, 525tds, 520d (the only four-cylinder 5-Series engine on this generation), 525d, 530d and M5.
1998 (pre-facelift) 535i SE Auto E39 saloon (UK spec).
From 1997–2000, the E39 model range in North America consisted of the 528i, 540i, and M5. In 2001, the 528i was discontinued and replaced by the 525i and 530i. The 520i, 523i, 525i and 528i were powered by a 110 kilowatt (150 hp) engine in earlier versions, a 126 kilowatt (170 hp) and 141 kilowatt (190 hp) engines respectively. These were all versions of the gasoline M52 inline-six engine. The 530i was powered by a 171 kilowatt (231 hp) inline-six, the M54, shared with the E46 330i. The 540i was initially powered by the 210 kilowatt (282 hp) 4.4 litre M62B44 V8 which was derived from the earlier E34 5 Series’ M60, but included upgraded cylinder block material, electronics, and more displacement. In September 1998, the 540i received the further upgraded M62TUB44, which was also seen in the E38 (7 Series) and in the BMW E53 (X5). This engine supported a VANOS variable valve timing system, and had electronic throttle control. It was slightly boosted to 290 hp for year 2002 and 2003 540i.