Convertible

A convertible, also known as a cabriolet, is a type of car designed to be driven with or without a fixed roof in place. Its defining feature is a roof structure that can be retracted, folded, or removed, allowing occupants to enjoy an open-air driving experience while retaining the option of weather protection when required. Convertibles occupy a distinctive place in automotive design, combining engineering complexity with aesthetic appeal and cultural symbolism associated with leisure, freedom, and motoring pleasure.
The design of a convertible presents unique structural challenges. Removing or reducing the fixed roof weakens the vehicle’s torsional rigidity, requiring substantial reinforcement of the chassis and body structure to maintain strength, safety, and handling characteristics. As a result, convertibles often involve additional engineering solutions compared with equivalent fixed-roof models.

Terminology and Nomenclature

A wide variety of terms are used to describe convertibles, reflecting regional preferences, historical usage, and marketing strategies. Common alternative names include cabrio, drop-top, drophead coupé, open-top, soft top, rag top, spider, and spyder. These terms are frequently used interchangeably, and consistent nomenclature is rare within the automotive industry.
The term cabriolet originates from the cabriolet carriage, a light, two-wheeled, horse-drawn vehicle with a folding top designed for two passengers. Over time, the word was adopted into automotive terminology to describe roofless or semi-roofed motor cars. In the United Kingdom, a two-door convertible was historically known as a drophead coupé, while a four-door open car was often referred to as a tourer.

Design and Structural Characteristics

The majority of convertibles use a folding roof framework, with the roof itself constructed from cloth or other flexible materials. This allows the roof to collapse into a compact space when lowered. Alternative designs include retractable hardtops, made from metal or rigid plastic, and detachable hardtops, which are manually removed and typically stored in the boot.
A significant drawback of convertibles is their reduced torsional stiffness due to the absence of a permanent roof structure. To counteract this, manufacturers reinforce the floorpan, door sills, windscreen frame, and rear bulkhead. These reinforcements increase weight and complexity but are essential for maintaining body rigidity, occupant safety, and acceptable noise and vibration levels.

Early History and Origins

Most early automobiles of the late nineteenth century were open-air vehicles with no roof or sides, closely resembling horse-drawn carriages. As engine power increased towards the end of the century, folding textile or leather roofs began to appear, inspired by carriage designs such as the Victoria and Landau.
Early roofed body styles included:

• Phaeton: a lightweight, open car with a temporary roof.
• Brougham or coupé de ville: featuring an enclosed passenger compartment with an exposed driver’s seat.
• Landaulet: combining a fixed roof over the driver with a folding roof over the passenger area.

Cheaper vehicles such as runabouts, roadsters, and touring cars often remained open or were fitted with basic folding tops and detachable side curtains.

Decline and Luxury Association

During the 1920s, advances in mass-produced steel bodies made fully enclosed cars more affordable. As a result, open cars gradually disappeared from the mainstream market. By the mid-1930s, convertibles were largely confined to the luxury segment, where style and exclusivity justified their higher cost.
A notable technological development occurred in 1939 when Plymouth introduced the first mechanically operated convertible roof, powered by vacuum cylinders. This marked a shift towards greater convenience and automation in convertible design.

Post-War Expansion and Popularity

Following the Second World War, demand for convertibles increased significantly, particularly in the United States. American soldiers returning from Europe had been exposed to small British sports cars such as the MG T-Type and Triumph Roadster, which were not widely available in the US during the war years. These vehicles helped popularise open-top motoring.
In 1948, Hudson incorporated convertible designs into mass-market unibody construction, further broadening their appeal. During the 1950s and 1960s, US manufacturers offered an extensive range of convertibles, from compact and affordable models such as the Rambler American and Studebaker Lark to luxury vehicles like the Packard Caribbean, Oldsmobile 98, and Chrysler Imperial. For many model lines, a convertible body style was offered alongside saloon and coupé versions.

Decline in the United States Market

Convertible sales in the United States peaked around 1965 and then declined sharply over the following decade. Several factors contributed to this downturn:

• The growing popularity of air conditioning, which reduced the appeal of open-air driving.
• The introduction of sunroofs and T-tops as partial alternatives.
• Noise, water leaks, and maintenance issues associated with fabric roofs.
• Higher motorway speeds, increasing wind noise and discomfort.
• Stricter vehicle safety regulations, which were more difficult and costly to meet with open-body designs.

By the mid-1970s, convertibles accounted for only a small percentage of total vehicle sales. Major US manufacturers progressively withdrew them from their line-ups, with Cadillac producing the last large-scale American convertible, the Eldorado, in 1976.

Revival and Modern Era

After 1976, factory-built convertibles sold in the United States were largely imports or specialist conversions. Coachbuilders produced limited-run models, including targa-top versions and dealer-available conversions. The American Sunroof Company played a significant role in this period, converting standard models into full convertibles and influencing manufacturers to reintroduce open-top designs.
During the 1980s, convertibles returned gradually to mainstream production. Chrysler introduced K-platform convertibles such as the LeBaron, Ford revived the Mustang convertible in 1983, and American Motors released a convertible version of the Renault Alliance. A major milestone came in 1989 with the launch of the Mazda MX-5, which became the best-selling convertible of all time and demonstrated sustained global demand for lightweight open sports cars.

Roof Types and Mechanisms

Convertible roofs can be broadly classified into textile and hardtop designs.
Textile (Soft Top) RoofsSoft tops are made from flexible materials supported by an articulated folding frame. Early versions used tightly woven cotton canvas, while later developments incorporated rubberised fabrics, vinyl, and polyvinyl chloride (PVC). Modern soft tops often include multiple layers, such as sound-deadening insulation and an interior lining to conceal the frame.
The folded roof and its mechanism are collectively referred to as the stack. Designs with a lower stack height produce a cleaner silhouette when the roof is down and may allow for rear seating, as seen in some mid-twentieth-century models.
Detachable HardtopsDetachable hardtops are rigid roofs made from metal or plastic that can be manually removed. They offer improved weatherproofing, sound insulation, and durability compared with soft tops. Popular from the 1950s onwards, they were often sold as optional extras and could include features such as heated rear windows.
Examples include early Ford Thunderbirds, Mercedes-Benz SL models, Chevrolet Corvettes, and various sports cars. Improvements in soft-top technology have reduced the prevalence of detachable hardtops, partly because they require separate storage space when not in use.