Drivers divided over hard or soft tops

With a growing number of folding hard-top coupés on the market, it appears these are the convertibles to head for

With a growing number of folding hard-top coupés on the market, it appears these are the convertibles to head for. But are they really as good as they seem, asks Daniel Attwood.

While they appear to offer the best of both worlds, coupé-convertibles come with a host of inherent problems.

Their roofs are complicated, heavy, need weighty motors, hydraulic cylinders and expensive sensors and require a stretched boot to accommodate the roof, which results in compromised styling and a car that often ends up being rear heavy.

Because of this, there is an apparent split between premium and mainstream manufacturers over whether to adopt folding hardtop technology. As a rule, it is the mainstream manufacturers who have chosen folding hardtops, while premium manufacturers, such as Porsche, Jaguar and BMW, have remained with proven soft-top technology.

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Because of the design and weight issues, convertible coupés often offer less passenger and luggage space, are slower and less fuel efficient and are less lucid in their designs.

Teething problems have also been common as manufacturers grappled with issues such as weather proofing and ensuring the reliability of motors and hydraulics. Peugeot was forced to address problems with the roof of early 206CCs, which were supplied by an Italian manufacturer.

"The early problems with the 11 micro-switches were due to the supplier's quality and were solved after a few months of production," says Martin Dunne, technical manager at Peugeot Ireland. But the company's reputation had been damaged and, for its newer 307CC, the French car builder uses a different roof manufacturer, which also supplies Mercedes-Benz with its SL and SLK folding roofs.

But such problems haven't stopped hard-top convertibles from becoming one of the most popular niche segments of the last decade.

They are the cars of the moment and clearly offer significant benefits in our northern European climate where they provide the ideal mix of open-top motoring when the sun shines and the hushed security, warmth and draughtt-free environment of a hard-top for the remaining 364 days a year.

And hard-top fans point out that traditional convertibles also have their inherent problems. "With soft-tops you have all the road and aerodynamic noises, where a [folding hard-top] vehicle in the coupé position is similar to a saloon in terms of road noise," says Dunne. "And the major advantage is that in 22 seconds you can have a cabriolet without leaving your seat."

Hard-top convertibles also come with glass-heated rear windows - a luxury that was the dream for early soft-top convertible drivers who were forced to contend with plastic rear windows misting up in winter.

Unlike soft-tops, the roofs of new hard-top convertibles are also not damaged by the elements nor are they the target for vandals. However, many of these soft-top issues have been addressed through higher quality fabrics and insulation as well as the use of real heated glass housed in the latest soft-top canopies.

While the popularity of convertible coupés has grown since the turn of the millennium, the concept stretches back for almost 80 years. Peugeot, which has a long association with ground breaking automotive technology, was the first to try folding hard-top technology in the late 1930s with its two-seater 301 Eclipse.

Ford followed in the late 1950s with its US-only six-seater Skyliner, whose folding steel roof took over a minute to automatically retract into the boot; in comparison today's CCs aim to have the roof stowed away while the driver queues at traffic lights. But reliability and high costs - Ford lost money on each of the 12,000 Skyliners it sold - meant failure was always on the cards for these early groundbreakers.

It took almost 50 years before attempts were made to reintroduce the market to folding hardtops. This time it was Mitsubishi's turn with the rare 3000GT Spyder of which only 1,600 were made.

But it was the Mercedes-Benz SLK, which was introduced with a folding hard-top in the late-90s, that is credited with being the first viable, affordable and technically sound convertible coupé.

Now, the market is flooded with hard-top convertibles, although they are clearly not for everyone. As Ian Callum, chief designer at Jaguar and the man responsible for the latest XK soft-top convertible, explains, when the company began exploring whether to keep the XK a soft-top, it found that there was a 50/50 split between customers' preferences for a hard or soft-top convertible.

While the plethora of hard-top convertibles is evidence that they offer what the market is looking for - convertible fun with the security of a hard top - there is a school of thought that rejects this hard-top philosophy. "For us to do a folding hard-top we would have to make the XK a two-seater and our customers did not want that," explains Callum. "We also found that the amount of extra space needed to accommodate a folding hard-top would clearly compromise the style of the car. A Jaguar's function is to be beautiful."

A Jaguar's function is also to offer exemplary performance and handling. The XK's all-aluminium chassis ensures that it is extremely rigid - 50 per cent stiffer than the outgoing model - and also extremely light. Adding the heavy mechanics of a folding hard-top would remove the advantages of the car's lightweight body and the fuel efficiency of the 300bhp 4.2-litre V8 engine.

So Callum took the decision to remain with a soft-top. "We know the consequences of not offering a folding hard-top," says the designer. "But we weren't prepared to allow style to be compromised." There was also the weight issue to consider. "With a folding hard-top, the weight distributionspreads over the tail," explains Callum. "And when you're driving a car of this type, that matters."

So with its soft-top, the €132,000 XK convertible remains light - it is almost 80kg lighter than BMW's soft-top 6 Series - meaning its power to weight ratio is impressive at 183bhp per tonne. Of course, the ability to automatically stow the lined and triple-insulated cloth and rubber roof within 18 seconds means there is still the need for weighty motors, which make the convertible 40kg heavier than the fixed roof coupé version.

Along with a plethora of other prestige manufacturers, BMW has opted to retain soft-top technology, this time for its latest 6 Series convertible. The company said the main reason for using a vinyl roof and hydraulic cylinders is the considerable weight and design advantage the soft-top offers. It also meant the convertible retained BMW's famous 50/50 weight distribution.