The danger with automotive brothers is fratricide. Remember the Pontiac Firebird? Chevy's Camaro sat on it like an elephant on a mouse, erasing most evidence of Firebird life. The Rover (Sterling) 800-series? Honda/Acura's Legend not only buried it in sales, the Honda/Acura example lived with the benefit of not falling to bits just out the dealer driveway. Cain often kills Abel.

Now, Fiat is giving birth to a twin son of a different mother. Never has such a sharply focused pair been based on the same flesh and bones as Fiat's new 2017 Fiat 124 Spider, which uses the exquisitely brilliant skeleton and muscles of Mazda's MX-5 Miata.

Specific Fiat sheet metal hides the MX-5 Miata origins, but genes are genes. The Fiat 124 Spider will be based on the very car that shamed the history of poor reliability of many in the small sports convertible fraternity.

There are slight differences. The Fiat grows a more protruding, higher nose with a bisected grille that recalls the original 124 Spider's, where the Miata uses a Mazda-family grille shape and more diagonal DRL slats at the edges. Larger Fiat headlamps hover over more rounded lower air intakes. Also, the new 124 has twin hood bulges, like the 124 gained in 1970.

We spoke exclusively with Fiat design manager, Felix Kilbertus about launching the Fiat in the shadow of the Miata, such a successful sports car icon.

"Fiat is the perfect brand for a car like this," begins Kilbertus. "Fiat stands for positivity, an optimistic outlook, the classic Italian 'bella figura:' high design without trying too hard. Italian products, food and design is credible at every level of the market including the affordable side and that is what guides us today as Fiat."

"We also do not want to get stuck in the past as some retro designs have done," notes Kilbertus. "We wanted to design a contemporary, beautiful sports car and then link it back to the original 124. We first aimed to create a true face," Kilbertus tells us. "A real eye at the headlamps links to the leading edge of the front grille. The lower air intake shows a bit of a smile and the overall balance of volume gives it a great presence on the road."

Indeed, the new 124 employs some key identifiable classic 124 features like the kicked-up character line mid-door at the shoulders and over the door handles; the gently sloping rear fenders down to meet the span of the trunk lid; even the hint of a Kamm shape at the tail.

Kilbertus told us that Fiat has very different requirements for the 124 than Mazda's regarding aerodynamic character, trunk capacity and the quality of materials. "We need to create a very strong Italian feeling and part of that recipe is inside with richer materials, unique design for the dash top and underside, unique numerals on the dials, even the steering wheel has a unique, thicker section width." The Fiat's seats are quite different from the Miata's, with conventional foam padding where the Miata uses lighter weight material and a mesh that conforms to the occupant's body. Also, leather upholstery will be optional.

While the design details of the original 124 Spider are largely present, the proportion and overall mass is not quite familiar, largely because the Miata has a variety of hard points in manufacturing that simply cannot be re-engineered without a total rethink, and that was certainly not going to occur. So, the new 124 tries hard to evoke the original, but in the process, it becomes part Honda S2000, part third-generation Miata, part amorphous.

The strongest attempt at resemblance to history is the grille's shape and the rounded headlamps and here is also where the new 124 seems to falter the most. The new Fiat's face is mildly cute, hints at familiarity, but it's nowhere near as appealing as the original's because the features conflict. Upper and lower grilles are rendered in a void of flat black and their shapes do not compliment each other. The turn signal and fog light cut outs are likewise shaped in a way that doesn't flow with other elements, resulting in a face with far too many large features (eight in all) conflicting with each other.

The 2017 124 Spider will be built at Mazda’s Hiroshima plant and powered by a Fiat 1.4-litre turbocharged four under the hood, making 160 horsepower and 184 lb-ft of torque. The Spider is about 100 pounds heavier and over five inches longer than the Miata. Sales will begin in the summer of 2016 with a special edition fitted exclusively with an automatic transmission. This seems to us like a hard rethink is in order to affirm sports car authenticity. A rumored Abarth edition, offering more power and greater performance may arrive a year into production.

The new 124 Spider surely builds on the huge capability of the MX-5 Miata and it will no-doubt perform as well or better in a straight line with more power and quite a bit more torque at low revs despite the weight difference. But the trickier challenge will be avoiding constant comparison to Mazda's roadster.

A brotherly fight seems inevitable.

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