In the four years since BMW launched its i8 Coupe, the company has sold 13,000 examples of the carbon-tub, petrol-electric hybrid. Customers have bought into BMW’s i-vision, to the point where they are demanding more from the Bavarian marque – including new models such as the i8 Roadster.
Never originally designed as an open top car, the only way BMW’s engineers could establish if a roadster variant of the i8 would be possible was to literally chop the roof off. And when the carbon-tub didn’t fold in on itself, BMW had another petrol-electric sports car on its hands.
The i8 Roadster’s roof is fully electric, and the switch to operate it is tucked away under the lid for the centre console storage compartment. It takes 15 seconds to go from fully open to fully closed – or vice-versa. There’s also a rear window that can be lowered with the roof closed (although not raised with the roof open) to allow more noise into the cabin.
While the folding roof robs the i8 of it’s Porsche 911-esque rear seats, BWW does compensate you with an additional 100 litres of storage behind the front seats. The rear boot remains the same as a Coupe, and is big enough for a generously-sized overnight bag.
While the roof may be fabric, the front half has a carbon-fibre panel inserted in it to maintain a sleek appearance and aid aerodynamics. The only additional strengthening is in the hollow A-pillars and header rail – required for the relevant rollover tests. In total, the i8 Roadster weighs 60kg more than the Coupe.
Removing the roof also required a few other tweaks to the Roadster’s body, including the fitment of a small splitter positioned behind the front bumper to balance the airflow and prevent the need for a rear spoiler. The vent on the bonnet also had to be closed – with the hot air from the car’s radiators now redirected under the car as opposed to over the windscreen and into the now open cockpit. Those trademark butterfly doors are new, too.
Accompanying the external changes, BMW has also fitted the i8 Roadster with its latest eDrive technology, which means the capacity of the lithium-ion battery has increased. This provides the electric motor with an additional 12bhp (now 141bhp) – boosting the car’s EV range to 33 miles. However, this increase in cell density does mean a longer charge time.
That improved battery range is instantly noticeable, too. Whereas in the original Coupe the electric motor could be easily side-lined by the turbocharged petrol engine, now the electrified elements of the powertrain are far more willing and able to take on longer and quicker driving duties. And when you’ve depleted the batteries, the brake regeneration and the three-cylinder petrol motor recharges them much quicker than before, as well.
New spring and damper settings have given the i8 Roadster a more direct front-end, although the electric power steering still has little feel, requiring a small leap of faith that the nose will go where you need it to. But there’s more grip, less understeer and the tyres work far harder than before.
Through quicker corners and on cresting roads, the i8 is now far more resolved, and inspires more confidence than the early Coupe. Combine a fully-charged battery with the three-cylinder engine – whose turbo you can now hear chuff away – and the i8 is now far more of a sports car than before.
Yet despite not being considered as a roadster from the outset, the i8 works remarkably well as a piece of design. In fact, with the roof open it’s more striking than its Coupe counterpart from every angle. However, it still requires an element of physical dexterity to get in or out.