New BMW Z4 and Z4 M Roadster Unveiled

Press Release

Chassis and Suspension

Ultimate Driving Pleasure

 

Model Updates – Detail:

 

·         Latest generation of DSC Dynamic Stability Control with additional functions.

·         Dynamic Brake Control (DBC) with emergency braking detection.

·         New suspension set-up.

The BMW Z4 Roadster offers the driver a very special suspension set-up perfectly prepared for sports motoring and simply ideal for driving to the ex­treme limit. And should the driver’s emotions and the thrill of sports motoring go beyond even these limits, sophisticated control systems guarantee active safety of the highest standard at all times.

Everything Required for a Perfect Suspension.

The dynamic performance, agility and sportiness of the Z4 Roadster rest on an extremely stiff, weight-optimised body structure and the special suspen­sion set-up for supreme dynamics. Carried over in its basic principles from the BMW 3 Series, the suspension has been modified in its spring and damp­er setting, as well as its kinematics and elastokinematics, being con­ceived
even more consistently for superior dynamics, agility, and handling. The new set-up also guarantees an even higher standard of motoring com­fort without impairing the agility of the car.

Well-balanced axle load distribution, a low centre of gravity as well as rear-wheel drive avoiding even the slightest effect of drive forces on the steering offers everything required for harmonious driving behaviour, optimum trac­tion and driving dynamics, as well as exceptional high speeds in bends. The very wide track of the car relative to the dimensions of the body, together with anti-roll bars on both axles, have a direct influence on driving stability the driver will feel and enjoy immediately: Compared with its competitors the world over, the BMW Z4 Roadster is most probably one of the most agile and dynamic roadsters to be found in the market. At the same time the low-slung seats moved far to the rear and the very direct feel of the steering give the driver immediate feedback on the car’s truly outstanding performance.

A spring strut axle with forged aluminium track control arms, twin-sleeve gas pressure dampers, rack-and-pinion steering, and anti-roll bars ensures opti­mum contact with the road at the front end of the car. The rear central arm axle with its twin-sleeve gas pressure dampers and anti-roll bar, in turn, pro­vides an optimum link between the rear axle subframe and the body of the car, allowing very safe handling and preventing uncontrolled steering ef­fects.

The driver in search of even more sporting performance has the choice of a special sports suspension lowering the entire car by 15 millimetres or 0.59´´ as an option. The runflat tyres featured as standard, in turn, have been spe­cially developed to reflect the sporting character of the BMW Z4 Roadster.

DSC Dynamic Stability Control for Supreme Driving Pleasure All the Way to the Limit.

Again reflecting BMW’s superior philosophy, the drive control systems are not used to enhance the suspension of the Z4 Roadster (simply because such an improvement is not required), but rather serve to increase driving pleasure and help the driver in mastering critical driving situations when go­ing to the limit. For the truth is that the chassis and suspension offer very substantial safety reserves to begin with.

The BMW Z4 features the latest generation of DSC Dynamic Stability Con­trol. This control system developed by BMW from the ground up is indeed increasingly becoming the key technology for the car’s entire system of elec­tronic management.

Originally DSC served “only� to apply the brakes specifically as required on individual wheels in order to enhance driving safety on slippery surfaces – for example in abrupt manoeuvres to avoid  obstacles or with the car threatening to become unstable in a bend. Today DSC offers a far wider range of functions in terms of sporting performance, safety, and comfort. In­tegrated ASC stability control, for example, monitors wheel spin by taking back engine power and torque when required, applying the brakes selec­tively on the drive wheels about to spin, and therefore re-stabilising the car whenever necessary. Yet another function of DSC is CBC Cornering Brake Control with its asymmetric division of brake pressure helping to prevent the car from swerving when applying the brakes slightly in a bend.

Higher Traction for Extra Drive Power.

The DTC Dynamic Traction Control function also integrated in DSC enables the driver to improve traction and, accordingly, the car’s drive power, not only on surfaces with a low frictional coefficient such as snow and ice, simply by pressing a button. For another option provided by DTC is to set the driving behaviour of the BMW Z4 Roadster highly individually and with a wide range of choice to a more dynamic style of motoring, enabling the driv­er to capitalise even more than usual on the sporting character of the BMW Z4 Roadster. As an example, DTC allows greater slip on the rear wheels adapted to current driving conditions.

DTC Dynamic Traction Control focuses on the enhancement of traction above all at low and medium road speeds, then gradually cutting back this function until the car has reached a medium level of lateral dynamics at speeds of about 70 km/h and/or lateral acceleration of approximately 0.4 g.

A further function is the additional adjustment of the car’s higher slip thres­holds by applying parameters such as the yaw angle and the lateral acce­leration of the car, adjusting the set-up of the suspension to current re­quire­ments in accordance with road surface friction and wheel spin. Depending on road speed, DTC thus allows a float angle of up to 20°, the Z4 Roadster maintaining the same agility as a sports car featuring a limited-slip differen­tial, without in any way impairing the safety function of DSC Dynamic Sta­bil­ity Control even when driving to the absolute limit.

DSC with New Functions.

The latest generation of DSC Dynamic Stability Control offers a whole range of additional useful functions such as ongoing Brake Pad Wear Control cal­cu­lating the remaining distance the brake pads are still able to cover and thus helping the driver organise maintenance requirements in good time. Another function is DBC Dynamic Brake Control maximising brake pressure when applying the brakes in an emergency.

Over and above these features, BMW’s new DSC Dynamic Stability Control offers various other additional functions: Hill Set-Off Assist applies the brakes automatically for a few moments to prevent the car from rolling back when starting on an uphill gradient and thus enables the driver to set off smoothly and easily without having to operate the handbrake. Automatic Fading Compensation, in turn, as well as Brake Standby automatically pre-loading the brake pads, serve to enhance motoring safety to an even higher level than before.

Automatic Dry Braking of the brake discs on wet surfaces improves the response of the brake system under such conditions.  

Electric Power Steering for Optimum Steering Control.

The sporting and agile BMW Z4 Roadster benefits in particular from rear-wheel drive characteristic of BMW’s driving philosophy and keeping the steering completely free of drive forces at all times. This guarantees excel­lent steering precision and gives the driver clear, unmistakable feedback informing him – or her – of the car’s current behaviour and handling requirements.

But the BMW Roadster offers even more, with the car featuring electro­mechanical power steering raising the dynamic and agile set-up of the Z4 Roadster to an even higher standard.

Referred to as EPS Electric Power Steering, this highly innovative steering system features an electric motor on the steering column and a worm gear supporting steering forces. In practice this means that steering forces are passed on to a mechanical steering transmission via an intermediate steer­ing shaft, the transmission helping to provide the right steering lock by means of tie-bars.

With the steering being controlled by sophisticated software, EPS allows a very high level of flexibility in the car’s steering characteristics, an optimum compromise between the steering damping effect and feedback from the road, as well as low steering forces at low speeds and when manoeuvring. A further important function is the very good centering effect of the steering, with the steering wheel returning perfectly to its straight-ahead position after a bend. And whenever the driver activates the sports mode on a car fitted with DDC Dynamic Drive Control as an option, steering assistance is re­duced to provide an even more sporting feeling on the road. A Servotronic function, finally, comes as standard.

Extra Comfort and Safety on Less Fuel.

With the adverse effects of bumps on the road or inadequate wheel balance not reaching the steering wheel, the driver benefits not only from a high stand­ard of steering comfort, but also from superior steering precision on bad roads.

Yet a further advantage of EPS Electric Power Steering is the reduction of fuel consumption, since the system does not require any energy when driv­ing straight ahead without any movement of the steering wheel. In practice, this means a reduction in fuel consumption of up to 1 litre every 400 kilo­metres or 250 miles compared with conventional hydraulic steering.

Optimum Brake Power.

It goes without saying that the brake system is perfectly attuned to the par­ticular character and performance of the Z4 Roadster. BMW’s engineers have focused above all, first, on the reduction of weight to an absolute mini­mum in order to optimise the agility of the Z4 Roadster. The second major benefit of the high-performance brakes is the improvement of stopping forces to an extremely high level and the enhancement of fading-free brake stability as well as optimum long-term brake forces.

The 17-inch brake system on the Z4 Roadster 3.0si is brand-new, featuring inner-vented brake discs front and rear. On all other Z4 Roadsters (with the exception of the Z4 M Roadster), in turn, the brake discs are inner-vented only at the front.

Runflat Tyres with Failsafe Performance.

The Z4 Roadster 2.5i and 2.0i come as standard on 225/55 R16 runflat tyres, the Z4 Roadster 3.0si features 225/45 R17 runflat tyres. Reinforced side flanks with additional inserts and temperature-proof rubber compounds, interacting with EH2 (extended hump) rims, prevent the tyres from being com­pressed under lack of pressure or jumping off the rims. As a result, the driver is able to continue for up to 250 kilometres or 155 miles on one or even several empty tyres, at a speed of up to 80 km/h or 50 mph and with an appropriate style of motoring. This means that under all reasonable con­ditions the driver is able to reach a service station without problems, not hav­ing to stop at a dangerous point or change the tyre himself. And last but not least, all control systems remain fully functional even in this case.

Tyre Pressure Warning.

The runflat tyres are combined with an electronic Tyre Pressure Control Sys­­­tem likewise featured as standard and warning the driver in good time of a possible loss of pressure by means of an optical signal in the dashboard. This system responds after just a few minutes on the road or, alternatively, at a speed of 15 km/h.

Benefiting from this early warning, the driver is able to fill up the tyres in good time, avoiding expensive tyre damage. For it is a fact that tyres lose their air instantaneously or rapidly only in 20 per cent of all cases.

In everyday motoring runflat tyres behave and drive in the same way as con­ventional tyres. And with the rims on the BMW Z4 Roadster being fully compatible with conventional tyres and wheels, the driver is able to fit a “normal� tyre whenever necessary.

Runflat tyre technology comes on both summer and winter tyres.