Why choose to steer

Urbanisation, traffic signs, lampposts and traffic islands: they all stand in the way when a truck and trailer combination enters the city. In addition to these obstacles, every truck must meet the legal requirements for the job. In order to deliver a load smoothly and safely into hard to access places, more and more trailers are being equipped with steering systems. Herewith an explanation why;

Non-steered trailer

If a semi-trailer is equipped with three fixed axles, it will turn using point ‘R’ as the pivot. When driving through a curve the vehicle combination will drive around point ‘P’. This is an intersection from the centerline of the rigid axle of the tractor and the centerline of the central axle of the semi-trailer. To move the semi-trailer in a forward motion, a force ‘Fv’ is required at each tire. However, while the tire is moving forward, the tractor pulls in direction ‘F’. It can be seen from this drawing that force ‘F’ is considerably larger than force ‘Fv’. The reason for this is that a friction force ‘Fw’ is introduced and therefore much more energy is needed to make a turn then when driving straight forward.

Steered trailer

If the third axle is steered so that its centre line also passes through point ‘P’, the
theoretical wheel base remains constant, and the wear on the tires of the two front axles
remains as if in a tandem configuration. The steered axle aligns itself with Point ‘P’ whereby friction is minimised. Alongside better maneuverability you will also profit from other benefits e.g.;

  • reduced tyre wear
  • less fuel consumption
  • less road surface damage
  • less transport movements