Posted on

2” and 3 1/2” king pins design and features

The king pin is a component of the coupling between the semi-trailer and the tractor unit.

Different designs make it possible to install king pins onto a trailer quite easily. JOST king pins satisfy the most stringent safety requirements. They are produced from high-quality, coated, forged blanks which are tested for the complete absence of cracks. Exchanging or converting our king pins is both quick and easy.

The king pins can be replaced or converted quickly and easily.

National regulations (in Germany §§19, 20, 21 of the “StVZO” Motor Vehicle Safety Standards) and JOST mounting and operating instructions must be observed for the installation, conversion and replacement of king pins.

For safety reasons, we recommend only using the screws once.

jost-king-pin-designsJOST king pin designs

Pins for retention plates with cone-shaped locating hole (flange).

Pins for dish-shaped retention plates (plate).
The pin is bolted to the retention plate and is easy to replace from underneath. 2” and 3 1/2” pins can be interchanged onsome types.

Pins without a retention plate. The pin is bolted to the top plate.

All the designs satisfy the requirements of the currently valid standards:

2” king pins (ø D = 2” ): dimensions as per Directive 94/20/EC – Class H50, DIN 74080 and ISO 337. 3 ½“ king pins (ø D = 3 ½“): dimensions as per DIN 74083, ISO 4086 and 94/20/EG.

The retention plate is welded to the skid plate. The relevant permitted load (D value) depends on the type of king pin and the skid plate thickness (A) in use and its bracing. Therefore, JOST installation instructions must be complied with. (Please also see our instructions for mounting and operation.)


The respective type designation is stamped into the pin and the retention plate. The type designation must match on both components. If several type designations are stamped into the retention plate, the pin may be changed for the typedesignation stamped into the retention plate. Example:switching from 2” to 3 1/2” pins. Legal regulations must be observed.

 d9f4a4c9e1 2b046d522a

Product overview

2” king pins for use with 2” fifth wheel couplings as per directive ECE R55-01 as well as DIN 74081 and ISO 3842.

3 ½“ king pins for use with 3 ½“ fifth wheel couplings as per directive ECE R55-01 as well as DIN 74084 and ISO 3842.

All king pins are suitable for use in self-steering axle systems.