Castor Correction – by Bushes, Plates, Drop Boxes or Trailing Arms or Drop Arms – for lifts 50mm or more. For lifts below 50mm (2”) it is advisable but not mandatory to add castor correction. Generally 4WD vehicles will have less Castor Angle than the equivalent year 2WD, and most 4WD’s will benefit with extra Castor above standard.
There are various arguments for and against the differing ways of achieving improved Castor Angles:
If the radius arm bushes are already worn (commonly the case), then replacing them with 2.5 to 3degree Off-set Bushes, makes perfect sense – assuming you have to do the bushes anyway.
Castor Plates result is approximately 5 degrees greater Castor, but do nothing to correct Steering Geometry problems.
Drop Boxes, Trailing or Drop Arms
Drop Boxes achieve the goal of greater castor but also have the advantage of putting the radius arms back to a more ‘normal’ geometry – ie horizontally pushing forward, rather than ‘angling down’. This improves stability. When the arms are at a steep angle it can feel a bit like you are driving on ‘stilts’.
For Patrol: the rear of the Trailing Arms have ‘T’ bushes where they mount into the chassis, the arms allow articulation by compression of the bush, if it is already under compression due to the ‘angling down’, there will be reduced movement of the arms, particularly droop.
Drop Boxes hang down below the chassis line and if you are sliding over rock ledges etc then this is a definite ‘hook-up’ point. New longer Radius Arms which result in an equivalent amount of Castor with good geometry.
So it depends on your budget and your use of the vehicle as to the best option to achieve greater Castor Angle.
For Nissan Patrol lifts over 50mm, the steering box will move ‘off-centre’ as the factory Drag Link (which goes from Steering Box on RH chassis to the LH front wheel) is non-adjustable.
So it is advisable to fit an HD Adjustable Drag link, to get the steering box back to centre. (especially the case when SRS airbags are fitted and removing the steering wheel is problematic).
Leaf Spring vehicles use Castor Plates to achieve replacement castor when required
For an in depth discussion about Castor Correction, read the 4×4 School article on Wheel Alignment.
For all enquiries to arrange a fitting, international freight costs or specific product information, please complete the form below or call 04999 85209