Challenges belt pretensioners |
Thursday, March 31st 2016
Read our Technology Update online

Find us at:      

Challenges belt pretensioners

Technology update March 2016

Car manufacturers are continually designing and producing cars that are safer and more economical, which means the potential dangers and challenges for emergency workers are also constantly evolving. The extension of the seat belt system with the lap belt pretensioner is a good example of this.

You can read more about this topic in this technology update!


The belt pretensioner is designed to keep the body of the occupant in place by reducing the backlash between the belt and the body. This prevents the occupant from sliding under their belt, called 'submarining', and thereby not being properly positioned to be protected by the airbag.

There are two different systems for tightening the belt: mechanical and the pyrotechnic belt pretensioner. In the first system the belt is tensioned by means of a prestressed spring. In the second system this is done by a pyrotechnic charge, which is also used to activate an airbag. Almost all belt pretensioners have been pyrotechnic since 2001.

In addition to the different activation systems, the belt pretensioners are divided in three different types:

  • Belt inertia reel pretensioner
  • Belt buckle pretensioner
  • Lap belt pretensioner


1. Belt inertia reel pretensioner:


2. Belt buckle pretensioner:

3. Lap belt pretensioner:

The inertia reel pretensioner belt and/or belt buckle pretensioner have been used for a long time, sometimes in combination with each other. In recent years we have seen a shift to a combination of inertia reel pretensioner belt and lap belt pretensioner.

The location of the inertia reel belt pretensioner and the lap belt pretensioner is much the same in most vehicles. It is almost always at the bottom of the B-pillar, inside of the seat. This is obviously an advantage for the emergency worker. They will be less likely to be faced with any surprises. 


However, it is different for lap belt pretensioners.. These are available in several versions and can be found in different locations:

  • Mounted on the seat
  • Mounted on the bodywork
  • Mounted on the B pillar
  • Mounted on the door

The following shows how the location of the belt pretensioner in the CRS corresponds to the type of belt pretensioner.


Mounted on the seat:
The location of the belt pretensioner on the seat is illustrated in the Crash Recovery System by the fact that the location of the lap belt pretensioner is also attached to the seat. If the seat is removed, the belt pretensioner will also go.

Jaguar - XE-Series - 4dr sedan - 2015-2016

Mounted on the bodywork:
The lap belt pretensioner here can be accessed by removing the side and seats. The lap belt pretensioner remains visible, which means it is attached to the bodywork. The Crash Recovery System also makes a distinction regarding the direction of the cylinder. The following illustration shows the cylinder of the lap belt pretensioner from the front.

Renault - Kadjar - 5dr SUV - 2015-2016

An example where the cylinder is pointing to the rear:

Hyundai - Tucson - 5dr SUV - 2015-2016

Mounted on the B pillar:
In this example, the lap belt pretensioner together with the belt inertia reel pretensioner are mounted on the B pillar. When tightening the lap belt pretensioner the belt is drawn upwards in the B pillar. In the Crash Recovery System the lap belt pretensioner, like the belt inertia reel, will also be removed together with the B pillar and door when removing the side.

Audi - Q7 - 5dr SUV - 2015-2016

Mounted on the door:
In some vehicles, mainly pick-up models, the rear doors and B-pillar are joined together. These doors are hinged at the rear. These kinds of doors are also called suicide doors. After opening these doors you have full access to the entire side of the interior. With the removal of the side in the Crash Recovery System, the lap belt pretensioner mounted in the door will also be removed. This also gives a good indication of the location and type of belt pretensioner.

Chevrolet - Colorado - 4dr pickup - Extended Cab - 2014-2016


Moditech naturally tries to display the lap belt pretensioner in the Crash Recovery System. An example of a new variation on the seat belt pretensioner can be seen below with the new Ford Mustang that was added to the CRS database in November last year.

Ford - Mustang - 2dr coupe - 2015-2016


Do not forget to download your database update!

Questions? You can reach us at