Is the folding hard-top doomed?

When first launched on the 1995 Mercedes-Benz SLK, the idea of a folding steel roof seemed too obvious and so clever that palms were slapped on foreheads across the motoring world.

The perfect symbiosis of convertible sunshine and weather-proof coupe? Of course buyers will love it. And they did.

Now though, the case for a folding steel roof seems less and less well made and according to the website BMWBlog, one of the most popular folding-steel-roofed cars is set to return to cloth-top when it is launched in 2021.

That car will be the next-generation 4 Series, the current model of which is the second generation BMW to use a folding steel hard-top. The current Z4 sports car also uses a folding hard-top, eschewing the fabric roof of the two preceding BMW sports cars.

Now though, the combination of weight and complication seems to have fatally holed the folding hard-top below the waterline. BMW's decision has also partly been driven by economics – it's codeveloping the next generation Z4 in conjunction with Toyota, which has mandated a lighter, simpler fabric roof for its new Supra, which will be spun off from the same set of common components.

Matching the technology with the next 4 Series makes perfect sense.

Image problem

There is also an image problem with folding hard-tops. Not long after Mercedes first re-introduced the technology (it had been around for decades, notably on models such as the 1950s

Ford

Fairlane but the SLK was the first modern car to deploy the tech)

Peugeot

brought it to the masses with the little 206CC, which was shortly followed by a larger 307CC and eventually a second-generation 207CC.

The cars were relatively affordable but the roofs suffered many mechanical maladies, often becoming stuck half way up or half way down. Similar issues struck such hard-top copycats such as the Volkswagen Eos, Renault Megane Cabrio and Opel Astra TwinTop.

Weight is also a primary driver of the change back to cloth roofs – in spite of both Ferrari and Mazda showing that folding solid roofs need not be that much heavier than a fabric one.

With every kilo counting towards a car’s Co2 emissions though, bulk and mass must be trimmed from every possible component and a well-engineered fabric roof will always be that bit lighter.

It brings BMW more into line with arch-rival Audi, which thus far has totally avoided folding hard-tops, an outlook increasingly being taken up elsewhere. Peugeot has never replaced the 307CC or 207CC and doesn't look likely to. VW has dropped the Eos and Opel went back to fabric for the TwinTop-replacing Cascada.

Supercomputer on wheels

While some will see that as a backward technological step, BMW is nevertheless ploughing ahead with high-tech developments for future models. Details of 2017’s new 5 Series are starting to emerge, and the car is looking more and more like a supercomputer on wheels.

BMW is apparently going to include a first-generation autonomous driving mode with the car, which will function at speeds of up to 80km/h and which will also keep you on track in motorway lanes, as well as taking care of parking.

The heads-up display will also take a massive leap forward with the inclusion of augmented reality, which will be able to alert drivers of upcoming dangers spots.