Back to overview
Intelligent Fastening Systems

Intelligent roof rail assembly: Solutions by WITOL

Intelligent fastening systems with stress-free mounting are crucial in the area of roof rails. They ensure that deformation of the car roof or loss of tightness are avoided. In addition, WITOLs also take into account the use of optical elements such as a very narrow roof railing. WITOL offers several systems for individual use.

The most important in a nutshell:

  • Meanwhile, the roof rails not only provide a practical mounting option, but also complete the design of a car. Both aspects are taken into account when using WITOLs.
  • Fast and stress-free assembly is made possible by WITOL’s individual tolerance compensation elements. Different WITOLs can be used for this purpose.
  • The WITOLs are designed as either a one-stage or two-stage system – depending on individual customer requirements.
  • The choice of system may depend on various factors (for example, design, width of the roof rails, mounting strategy).

Roof rails as an eye-catcher and functional element

Roof rails are a popular method of attaching sports equipment or other bulky loads to cars. In addition to the fastening, one criterion in particular is now increasingly decisive for the roof railing: the design. The railing can be individually adapted to the vehicle design and enhance it. From a practical point of view, it allows convenient transport of loads that turn out too big for the trunk.

The challenge here is that car roofs must not be deformed under any circumstances, not even by an attached roof railing. In addition, the roofs must be 100 percent leak-proof – this factor must not be influenced by a roof railing. In addition, extremely strong forces act on the railing and its screw connections in tight curves or during emergency braking. The roof structure must be attached to the railing in such a way that no additional safety risks arise for all road users in these hazardous situations.

Fastening solutions from WITOL

The fastening solutions from WITOL address this problem. They enable tight and at the same time stress-free fastening of the roof railing – both on car roofs with roof duct and on laser-welded models. The railing is firmly and securely connected to the supporting structure of the car body via several screw points.

There are two different systems for mounting the WITOLe:

The one-step system

With this system, the compensation of tolerances between the supporting structure inside the vehicle and the outer roof skin takes place automatically. Several WITOLe are inserted into the roof skin. A screw activates the automatic tolerance compensation and connects the respective components via the WITOLe. The WITOL compensates for the tolerances and ensures the tightness of the entire connection.

The two-step system

This system can be compared in its function to a precise envelope, which closes the gap between the supporting structure and the outer roof skin. The tolerances are compensated manually in this system: In the first step, the WITOL is placed in the vehicle and activated by an assembly tool. In the second step, the railing is installed using a conventional screw connection. A screw connection by means of stud bolts can also be used for this purpose, for example.

Both systems have their advantages and can be individually adapted to the requirements of the assembly. Which system can be used depends on various factors. Single-stage systems have a higher space requirement and can therefore be used with wider railing systems without any problems. A delicate railing, on the other hand, requires a space-saving two-stage system. Likewise, the two-stage system must be selected if a stud bolt is to be used for the screw connection. Furthermore, cycle times and assembly sequence can be decisive for the use of one of the two systems. The goal of each system is to fit seamlessly into our customers’ production.


WITOL as a practical and reliable solution

High demands on fastening solutions for a roof railing also result from the relevant safety aspects. In addition, the design of the roof rails plays a decisive role for the overall appearance of the vehicle. WITOL’s tolerance compensation systems were developed specifically for these needs. Due to the efficient and tension-free fastening of the roof rails with WITOL, all aspects are taken into account.