The open air experience of a convertible certainly is sensational. Feeling wind, light and sun heat generates a unique driving feeling, hardly to be compared with any other driving pleasure. Driving around in an open convertible may be fabulous, these fun models are quite impractical when the weather does not co-operate. If you opt for a bit more light and air in a normal car, there are other solutions.
Traditional, though old-fashioned – the steel sliding sunroof
Until recently the sliding roof was a standard optional extra in many cars, which could be ordered at purchase of a new car. A steel sliding roof consists of a punched out part of the roof panel, equipped with a mechanism. The steel sliding sunroof is discreetly pulled back under the other roof part with an electrical or manual hoist, giving the driver a whiff of the convertible experience.
Unfortunately the steel sliding sunroof has several disadvantages. Firstly, the mechanism: many constructions suffer from jamming parts, breaking off, developing play or sustaining another defect. The mechanism is hidden under the ceiling cover, making repair complicated. Furthermore, spare parts are difficult to obtain, even for more recent car models. Steel sliding sunroofs are not as susceptible to damage as electric folding roofs, although when they jam, it can become expensive.
Sliding roofs are prone to leak. Hardly any construction is an exception. Fitting in a clean gasket between sliding element and the rest of the roof panel is a rather cumbersome installation. When the rubbers become brittle or start to shrink, the tightness is the first thing to be compromised. Water drips on the driver when it rains or when visiting the car wash – not really a pleasant feeling. Although this repair is not as complicated as defective mechanism, it is still a nuisance.
Ultimately, wind noises used to be a constant companion of sliding roofs. Several solutions were developed such as attaching draught stops in front of the openings. Although thesed were effective, they did not look attractive. Furthermore, they caused an increase of air resistance and therefore of fuel consumption as well.
The 80ies and 90ies saw a trend of retrofit sliding roofs, for which a hole had to be cut in the roof. There was an option for a pop-up roof or an installed sliding roof on the car. These solutions were tolerable at best and caused a decrease in value of the car, rather than an increase.
Off through aerodynamics
Nowadays, the sliding roof is becoming increasingly problematic due to the complicated bodywork shapes. The roof element requires insertion between ceiling and roof panel, which demands a flat roof.
The strongly curved roofs of many modern cars make the installation of a sliding roof almost impossible. Insofar it is still available, a compromise applies. In the Hyundai IX20 the sliding element slides over the top of the roof, thus protruding in the wind stream during driving and compromising the aerodynamics. Furthermore these solutions are bound to generate wind noise. The final end of the sliding roof is therefore in sight.
Mostly extinct: Targa top and T-bar
Unfortunately, the practical sunroof versions “targa top” and “T-bar” have become almost extinct. Both solutions almost succeeded in merging convertible and coupé. The targa top allowed for removing the middle section of the roof. Pioneer and main supplier of this solution was Porsche with the 911. From the 70ies until the 90ies the Baur company equipped the contemporary BMW 3 models with targa tops.
It had the advantage for the driver of obtaining a convertible experience, although the car was considered a closed sedan, providing a financial advantage with respect to tax and insurance obligations. With their look, Baur convertibles could never compete with the real BMW convertibles. Targa tops have all but vanished today.
The T-bar (T-top in America) was rarely found on European cars. Mainly US-American coupés gained fame with this equipment feature. Firebird, Camaro, Corvette or GTO with their T-bar were considered closed coupés. The almost fully removable roof made these cars as good as convertible.
Technically, the T-bar differs from the targa top due to the remaining rigid bar in the middle, dividing the roof into two separate halves, which were removable. This had its advantages for the sturdiness of the bodywork. The roof is not interrupted, making structural fortification of the underbody unnecessary. Nevertheless, the T-bar has also practically vanished from the market. This is somewhat unfortunate. A specific advantage of the two small roof halves of the T-bar was the fact that they were easily stowed away.
As an alternative for the loophole: the panoramic roof
In the 1950ies the panoramic windscreen was a standard equipment feature for cars. It was recognisable by the A-pillar. Instead of a straight, full-length support, the A-pillar was curved like an S or C-shaped component. The fitting windscreen provided an excellent all-round view. Particularly the driver’s vision was free from interrupting supports.
This solution had a serious disadvantage: it weakened the bodywork extremely, especially in the roof area. In case of an accident even the large American road cruisers collapsed like cardboard, and many paid with their lives for this comfort.
After about 20 years, car construction has made a turn. Instead of thin and brittle A-B and C-pillars and huge glass surfaces, contemporary cars have the opposite: thick, sturdy supports and windows becoming smaller and smaller, turning cars into fortresses.
The effect has its price. Cars were never as safe as they are now – and the all-round view was never worse. Technologically this is compensated for with rear-view cameras, parking sensors and Parktronics, although no one is really happy with the dark capsules of today’s car interiors.
The new trend is once more “panoramic roof“, with a large glass panel replacing the front part of the roof panel, in fact enlarging the windscreen. Contrary to the cars from the 50ies, the windscreen is simply extending onto the front roof. Although this does nothing to improve the view for the driver with respect to other traffic participants, it generates a more comfortable driving experience as once more, plenty of sunlight can enter the car.
Not all advantages
In standard cars, the panoramic roof is a rigid element, which can not be opened. Passengers experience the light shower of the convertible without the fresh air if the panoramic roof if it is not equipped with a sliding roof – with its own earlier mentioned disadvantages.
Real convertibles with folding roofs generally are equipped with panoramic roofs. Renault was a pioneer in this field. Meanwhile, other manufacturers followed and offered it as an additional feature.
Technically glass pop-up roofs are not inferior to their metal counterparts. The hard glass is a lot less impervious to slight impacts such as hail, tree branches or small grit than the thin bodywork metal.
When closed, panoramic roofs amplify the terrible greenhouse effect in the car. Ordering a car with a panoramic roof without air conditioning can be regarded as useless. When parked, cars with panoramic roofs are extremely dangerous for everything and everybody remaining in the car. Children and animals suffer after only a short period of time. Therefore, handling a car with a panoramic roof requires sensible practice.
Hardly solvable conflict
Light and air versus safety and driving comfort – the balancing act between driving pleasure and practicality must go into the next round for the sunroof. In a technical sense, the conflict between the dreary coupés and the exciting convertibles can hardly be solved. Many of the intermediary solutions and compromises bring more problems than advantages.
At a certain point a solution could be a flexible screen installed on the ceiling. This would provide a convertible experience for the passengers without compromising the sturdiness and safety of the bodywork. Never say never. The car industry has come up with a lot crazier things…
Foto: Babich Alexander, vpilkauskas, pingphuket, Khimchenko Klim, koya979, SofiaV, Mihalex, ARENA Creative, Olinchuk, Bobkov Evgeniy / shutterstock.com