Rear axle with reinforced suspension and modified air flow.
On the rear axle the V-bars already featured on the Coupé and Saloon to provide the necessary reinforcement have been extended all the way to the side-sills. This configuration enhances chassis stiffness around the rear axle and provides appropriate axle kinematics for a car with supreme engine power and sporting performance all round. In addition, the engineers at BMW M GmbH have modified the flow of air beneath the car at the rear to the change in design and construction, thus ensuring optimum cooling on the final drive.
In its overall construction, the five-arm rear axle is designed consistently for minimum weight. The anti-roll bar, for example, is a hollow tube in the interest of significant weight reduction. So despite the slightly larger diameter of the tube than on the Coupé, the anti-roll bar on the BMW M3 Convertible offers an ideal combination of superior efficiency and low weight. Together with the axle arms made of forged aluminium and the aluminium dampers, the reduction in weight ensured in this way adds up to approximately 2.5 kg.
The front axle assembly is the same as on the Coupé and Saloon, with nearly all components on the double-arm front axle made of aluminium. A high standard of lateral stiffness at the front reflecting the superior power of the engine is ensured among other things by extra-stiff spring struts, swivel mounts and axle supports specific to BMW M, and an additional light-alloy reinforcement panel beneath the engine. And like the anti-roll bar at the rear, the anti-roll bar on the front axle is also a tubular structure serving to optimise its functions and minimise its weight.
Compound brake system and forged light-alloy wheels.
The new BMW M3 Convertible comes with the same extra-large compound brakes as on the Coupé and Saloon. The inner-vented, cross-drilled grey-cast iron brake discs measuring 360 millimetres/14.2´´ in diameter at the front and 350 millimetres/13.8´´ at the rear are connected to the aluminium disc support by stainless-steel pins cast into position.
With this configuration significantly reducing the thermal loads acting on the brake discs, brake performance and service life are enhanced accordingly.
A further advantage of this high-performance brake system is the additional reduction of weight where it really counts, that is on the car’s unsprung masses.
An ongoing, continuous wear indicator permanently monitors the condition of the brake pads, a display in the cockpit informing the driver of their remaining service life. This not only enhances safety on the road, but also avoids unnecessary service and maintenance.
The underpressure required for the brake servo is generated by an electrical pump independently of engine speed.
The new BMW M3 Convertible comes as standard on forged light-alloy wheels in BMW M design. Rim dimensions are 8.5 x 18 inches at the front on 245/40 low- profile tyres and 9.5 x 18 inches at the rear on 265/40 tyres.
Servotronic with two control maps for optimum steering power assistance.
The new BMW M3 Convertible comes with rack-and-pinion steering featuring hydraulic Servotronic support. Servotronic reduces the steering forces required, with the degree of power assistance related to the speed of the car on the road.
At low speeds, therefore, Servotronic provides a lot more steering support to reduce the steering effort, for example when parking. At high speeds, on the other hand, power assistance is reduced accordingly in the interest of enhanced directional stability.
Using the optional MDrive configuration system, the driver is able to pre-select the actual effect and assistance factor provided by Servotronic following either the Normal or the Sports control maps.
In the Sports setting, Servotronic gives the driver a particularly direct feeling for optimum feedback on road conditions. On winding country roads and at high speeds this enables the driver to steer the car with unparalleled precision. In the Normal mode, by contrast, power assistance is increased consistently throughout the entire speed range.