Wind deflector principle


Absolute windlessness in an open roadster or convertible is not possible - while driving. A mild breeze is quite pleasant in the summer, but a draught on the neck and joints can be stressful in the long term. The only thing that can help is a wind deflector as a preventive measure and to start or extend the open-top driving season earlier.The effect of a wind deflector is not the same for all vehicles, depending on their design. The shape and length of the vehicle, the position of the windshield, the size of the side windows and the shape of the exterior mirrors all cause the wind to flow and swirl around the body of the vehicle in very different ways. With some vehicles a wind deflector therefore brings almost no wind, with others noticeably less. A wind deflector helps protect the head, neck, kidneys and joints from strong drafts.

Basically, the tighter the wind deflector is fitted behind the seat, the more effective (+ it is. The side windows must be closed. The wind deflector must not be positioned too high (approx. headrest height, depending on the seat setting), otherwise it will catch the airflow from the front and the opposite effect will occur. As speed increases, the airstream descends at an ever shorter distance from the windshield frame and also enters the vehicle from the side, at the end of the side windows. For the best effect, therefore, the wind deflector is mounted so that it sits directly behind the seats, at headrest height and in the area of the side windows (Fig.).

The material the wind deflector is made of is largely irrelevant, as even a fine-mesh net deflects the airflow almost as well as a glass or acrylic pane; the difference lies primarily in its appearance.

Various vehicle concepts and wind deflector designs are shown below in terms of their mode of operation:


The wind deflector is attached to the body, interior trim, roll bar, head restraints or seats. It is important that the lower edge of the wind deflector is tightly sealed to the body or the trunk partition - if necessary with a cloth, cushion or tarpaulin, so that the air vortices deflected downwards by the wind deflector cannot flow forward between and next to the seats.


The wind deflector is attached to the interior trim on the right and left - usually in sockets provided at the factory - to the head restraints or seats. The airflow diverted downwards by the wind deflector is sealed off from the vehicle interior by a mesh-covered frame, panel or tarpaulin.

Fig. 1 shows a wind deflector with a plate or frame, usually connected by an articulated joint. The plate or frame sits horizontally, is detachably anchored at four points on the interior trim and directs the air vortices directly out of the vehicle. The rear seats are firmly covered. The steep position of the windshield causes the airflow to break off early.

Fig. 2 shows a wind deflector with a tarpaulin stretched downwards directly behind the seats, thus leaving the rear seats free. The wind deflector and tarpaulin thus form a partition between the front and rear seats. The tarpaulin can optionally be stretched over the rear seats as shown in Fig. 1, and only one seat can be covered by a zipper. In this example, the windshield is pulled far back, and the air vortices are created further back, depending on the speed.

Fig. 3 shows a vehicle with a spoiler on the upper edge of the windshield. In addition, a rear seat wind deflector is mounted between the rear head restraints. By raising the windshield with a retractable spoiler, the airflow is guided upward, thus falling only after a greater distance and being diverted by the rear seat wind deflector.

The examples shown may vary, depending on vehicle concept and speed. Depending on the interior length, height and position of the windshield, a rear-seat wind deflector, even without a spoiler on the windshield frame, is usually sufficient for the rear and front seats at city to highway speeds. As speed increases, the air vortices intensify and the airflow drops earlier, so that the front wind deflector becomes essential for good wind protection.


Classic cars have much steeper windshields and side windows, so that the airflow drops very early. In this respect, a wind deflector should be installed close behind the driver's seat and relatively low. Since classic cars are not prepared for wind deflector installation, it is preferable to use clamps that do not alter or damage the vehicle in its original condition.

© auco auto-comfort GmbH 09/2016 - Reprint only with permission of the author