DETROIT MOTOR SHOW: Alfa Romeo 4C Spider

Alfa Romeo has lifted the lid on its mid-engined 4C coupe, revealing the all-new 4C Spider overnight at the 2015 North American International Auto Show.

While the fixed-roof 4C coupe is still a month away from Australian showrooms, the 4C Spider will arrive at least six months later, in the second half of this year. Of the 300 or so 4C to be delivered over the car's life cycle, only about a third will be Spiders.

Naturally, the drop-top 4C will be more expensive than the coupe, of which Australian pricing is expected to be revealed within weeks, but the Spider will offer almost identical performance since it's based on the same carbon-fibre monocoque chassis and weighs almost the same.

That's right, at 1060kg dry (1128kg kerb) in North American spec, the Spider weighs just 10kg more than the equivalent coupe and offers the same 41/59 per cent front/rear weight distribution.

A slightly less aerodynamic body (0.341 v 0.335Cd), 2mm taller overall height (1185mm) and 1mm lower ground clearance (113mm) are the only differences in specification.

That means the two-seat 4C Spider features the same mid-engined, rear-drive layout as the coupe, and the same transverse 177kW/350Nm 1750cc turbocharged four-cylinder petrol engine, matched to Fiat's six-speed TCT twin-clutch automatic transmission.

Alfa says the 4C Spider sprints to 100km/h in less than 4.5 seconds and can generate 1.1 g of lateral acceleration and 1.25 g of maximum braking deceleration.

Of course, the key difference to the coupe is the Spider's folding cloth roof (and an optional carbon-fibre hard-top, which will become available later), which attaches to the car via a carbon-fibre windscreen frame.

The Spider also features different headlights and the option of a new Akrapovic performance exhaust system with twin central outlets, as seen on the 4C Spider concept at the Geneva show.

Inside, there's a driver-oriented cockpit with flat-bottom, leather-clad steering wheel, paddle-shifters, full leather trim with accent stitching, carbon-fibre air-vent surrounds, aluminium pedals and a 7.0-inch colour information display.

To this the 4C Spider adds a new premium Alpine sound system with Bluetooth phone connectivity and music streaming, USB port, iPod interface and CD/MP3 capability.

The 4C Spider will be available in seven exterior paint colours: Rosso Alfa, Black, White, Basalt Grey Metallic, Rosso Competizione Tri-coat, Madreperla White Tri-coat and all-new Giallo (yellow).

Six interior combinations will be produced, including two seat materials: Black leather with red accent stitching, red leather with red accent stitching and new black leather with Giallo accent stitching.

New for the 4C Spider is contrasting Tobacco leather with black accents – with the same two-tone combination on the instruments, door panels and steering wheel – which will become available later.

The Spider also brings four new wheel designs, although the standard wheels remain 17x7.0-inch (front) and 18x8.0-inch (rear) cast alloys and there is the option of larger 18x7.0-inch (front) and wider 19x8.5-inch (rear) forged alloy wheels – also in silver or dark grey.

Rounding out the personalisation options are four brake calliper colours: standard silver or red, yellow and black.

Finally, a Track Package will also be offered for the 4C Spider, comprising high-performance shock absorbers, front/rear sway bars, the larger 18/19-inch wheels with Pirelli P-Zero AR Racing tyres, a 'performance' steering wheel with microfibre inserts, carbon-fibre exterior mirrors and gauge cluster bezel, and the option of black leather 'performance' seats with microfibre inserts and red or yellow accent stitching.

Alfa says the North American-market 4C Spider comes with stiffer springs, larger anti-roll bars and retuned shocks as standard, but it's not yet clear which tune Australians will be offered.

"Adding to the excitement of the 4C Coupe, our all-new 2015 4C Spider expands the brand's product offering and continues our mission of building great Alfa Romeos," said Reid Bigland, Head of Alfa Romeo North America.

"With a removable carbon-fibre hard-top, the 4C Spider takes the coupe's supercar level of performance and technology and 'opens it up,' allowing the driver to experience the incredible 4C from an entirely different perspective."

The Modena-made 4C Spider is the first of three all-new rear-drive roadsters to come from the Fiat Group. It will be followed by a Japanese-built Fiat- or Abarth-badged version of Mazda's next MX-5 and a convertible based on the same 'Giorgio' platform as Alfa's belated 159 replacement.