Driving without a roof and possibly also without bothersome roll bars should in this way be made possible. If it starts raining the roof generally offers protection at the push of a button. The safety aspect should not fall short and all the safety and comfort features of vehicles with a solid roof should also exist. In spite of these problems and also the high prices, convertibles are as popular, especially in Germany, as never before.
How it works
The designing of a cabriolet shows, how much the roof and the glued windows contribute to the stability. The strengthening in the car body increases the weight by approx. 100 - 200 kg. Nonetheless, a convertible car body is not as quiet or stable, even when the roof is closed, as a car with a solid roof. For this reason, many convertibles need, in addition, a vibration absorber. These are made up of one or two heavy weights which are mounted on supporting insulators and reduce vibrations in the car body by producing counter-vibrations. One can imagine how considerable the expenses are to the manufacturer when building a convertible.
The fuel consumption of a convertible can only be reduced by driving at a slower speed. Technically, it is not at all suitable for economical driving. Apart from the higher weight the drag coefficient and sometimes also the cross-sectional area are greater. Should anyone wish to translate engine power into effective propulsion, they should not chose a convertible. As far as safety is concerned, it also does not cut a good figure. Except for an A-pillar which is not joined to the roof at the back and a reinforced door-sill the convertible has much less to offer against side impact than a closed coupe. If no roll bar exists, the B and C pillar are missing completely. At least, the manufacturers have done something for the protection in the event of overturning. If there is no roll bar, its absence is compensated for by bars integrated into the headrests or in the event of an accident, very fast reacting snap-up protection bars. The frame around the windscreen is also strengthened. Folding, solid roofs which substitute for the hardtop were previously just used in winter.
Other disadvantages of the convertible have also been reduced. For example, the trunk capacity can be increased, at least when the roof is closed because the roof tub made from solid sheet-metal has been omitted. Nevertheless, in four-seater convertibles there is less space for passengers using the rear seats. With two-seaters, called roadsters, the seating capacity is already limited.The electric or hydro-electric triggering of the roof is especially spectacular. For safety reasons this is possible only when the vehicle is stationary or moving very slowly. Besides, not all convertibles are automatically centrally bolted down, either in the middle or by means of two locking clamps on the left and right above the windscreen. If a solid cover exists for the opened roof, at least, in this respect, everything in the rear has been taken care of. If not, then the protective covering (tarpaulin) must still be pulled over the folded roof. With some small series vehicles this can be a time-consuming affair. If, however, no sharp edged parts protrude, driving without a tarpaulin is also allowed. However, without a tarpaulin the interior lining can pick up a lot of dust.
A roof needs care, and does not, as a rule, last as long as the vehicle itself. The longer it remains in an open state, the more pronounced are the folds which will tear after some time. Moisture can also produce unpleasant discolouring. With synthetic rear windows special care is necessary when folding. Also the roof must always be kept clean because dirt particles can grind fine grooves into the synthetic rear window when folded. At least with a synthetic roof one can still run the car through a car-wash, with a material roof this is, as a rule, not permitted. Even more care is necessary in this case, e.g., brushing the impurities away with clear water. Only when the material is completely dry, can the impregnation be undertaken. Best of all, one should buy a roadster that has a short and generally very simple roof. A Spider is even better, it has, generally no roof at all!. Indeed, one must take into consideration, that when it rains, e.g., one has to stop on the shoulder of the highway, and in a traffic jam, open an enormous umbrella, which is not allowed anyhow. 09/08