Driving Dynamics Paramount in New BMW Z4 Roadster

MUNICH, Germany – The third-generation BMW Z4 has reached the final phase of development ahead of the new 2-seater’s planned public debut at the Pebble Beach Concours d’Elegance in Monterey, CA, in August.

The ʼ19-model-year roadster has been re-engineered from the ground up with a more contemporary platform and, according to the German automaker, more sporty handling traits than the second-generation model it replaces – the so-called E89 introduced to the BMW lineup in 2009.

With less than three months until its world premiere, BMW indicates the new Z4’s engineering focus has switched from all-out durability testing to more detailed fine-tuning of its chassis. Much of the car’s recent development has taken place at the company’s Miramas test track in southern France, where future models can be tested away from the public eye on a variety of different test tracks, ranging from a high-speed bowl to tight and twisting handling circuits.

Previewed in concept-car guise at last year’s Pebble Beach Concours, the new Z4 is larger than the third-generation Z4, with wider tracks giving it a more confident stance.

“A shorter bonnet and crisp overhangs ensure the driver sits closer to the center of the car than in previous BMW roadsters,” BMW design boss Adrian van Hooydonk says.

The new Z4 shares key elements of its platform, inner body structure, chassis and electrical architecture with the revived Toyota Supra, which is due to make its public premiere in January at the North American International Auto Show in Detroit. But while the Z4 sports the folding fabric roof structure worn by the prototypes shown here, the new Supra will be sold exclusively as a fixed-roof coupe.

Replacing the folding hardtop arrangement of its predecessor, the new Z4’s fabric roof is claimed to open and close in just 10 seconds at speeds of up to 31 mph (50 km/h). When the roof is stowed behind the cabin, the new roadster offers up to 8.1 cu.-ft. (229 L) of cargo capacity – some 1.7 cu.-ft. (48 L) more than the model it replaces, according to BMW sources.

The Z4 and Supra, which will be produced together by contract assembler Magna at facilities in Graz, Austria, also will share drivelines, with the Toyota adopting specially tuned versions of BMW’s inline 4- and 6-cyl. engines and ZF-engineered 8-speed torque-converter-equipped automatic transmission.

BMW has revealed only limited details ahead of the new roadster’s world debut. It does confirm the new Z4 lineup will be headed by a range-topping Z4 M40i M-Performance model. It is expected to receive the same turbocharged 3.0L inline 6-cyl. gasoline engine as that used by the X3 M40i.

Producing 355 hp at 5,500 rpm and 369 lb.-ft. (500 Nm) of torque at 1,520 rpm, it promises to endow the new open top with the sort of straight-line performance to challenge the likes of the Porsche Boxster S, which runs a turbocharged 2.5L horizontally opposed 4-cyl. engine with 345 hp at 6,500 rpm and 310 lb.-ft. (420 Nm) at 1,900 rpm.

To put the power to the ground, the rear-wheel-drive Z4 M40i has the same rear axle as the M3 with an electronically controlled differential. In the top-of-the-line Z4 model, it is mated to a standard 8-speed automatic gearbox.

Other engines likely to be offered include a turbocharged 2.0L gasoline engine. It is expected to develop 181 hp and 214 lb.-ft. (290 Nm) in a planned entry-level Z4 sDrive20i model and 248 hp and 258 lb.-ft. (336 Nm) in a midrange Z4 sDrive30i model. Both are expected to offer the choice of either a standard 6-speed manual or optional 8-speed automatic gearbox.

BMW says it has conceived the new Z4 as a more driver-oriented model than its predecessor. “The whole concept behind the new car is geared more towards agility and driving dynamics,” explains Jos van As, head of chassis development. “The high level of body stiffness (and) a very rigid suspension attachment provides the perfect basis for a setup that guarantees the performance qualities of a genuine sports car in terms of steering precision as well as longitudinal and transverse acceleration.”

To heighten the Z4’s handling qualities, BMW says it has fitted the range-topping M40i model with a lowered sports suspension featuring adaptive damping control, a newly developed front axle, different-sized wheels and tires front and rear, and an M-Sport brake package.

An independent appraisal of the ʼ19 iteration of the Z4 will have to wait until the first test drives later this year.