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Tougher Control Arms

by Superior Engineering

Michael Hayes explains why your 4X4 needs heavy-duty trailing arms.

Heavy-duty Upper and Lower Control Arms

Original factory control arms are normally made with light-duty off-road touring in mind and aren’t up to the task when it comes to real off-road use. In response to the need for heavy-duty upper and lower control arms, many companies now produce upgrades for most popular applications. The strength, durability and price of these heavy-duty arms can vary greatly, and some manufacturers can supply both fixed and adjustable options depending on the vehicle requirements.

The lower rear control arms that form part of the rear suspension are one of the most commonly abused and damaged components when driven off-road. They are generally the last thing that gets in the way when trying to climb ledges or rocks, and more often than not you are under a bit of power and most of the vehicle weight is on the one control arm. This situation worsens once you lift your vehicle: the once near flat lower arms are now are on an angle and are in a vulnerable position.

Under load or acceleration, the rear arms once damaged can bend uncontrollably as the forces they are subjected to from bouncing or trying to climb obstacles transfers a tremendous amount of load into the arm, much like standing on a Coke can - sure it can take your weight until it has a small dint and then it crumples! The same goes for aftermarket arms that are pre-bent - they must be dramatically stronger in design to account for the reduction in compressive strength.

The rear of a 4X4 with heavy-duty trailing arms
Figure 1 : Heavy-duty 4WD trailing arms in action

When the rear suspension is lifted, the axle will rotate forcing the differential pinion to point away from the transfer case in most cases. The result is the pinion angle of the rear differential and the flange on the transfer case are no longer parallel. This can introduce vibrations in the driveshaft. By installing modified length or adjustable rear control arms, you can rotate the pinion to the correct angle, reducing the chance of vibrations.

Lower rear control arms
Figure 2 : Lower rear control arms are generally the last thing that gets in the way when trying to climb ledges or rocks

Fixed-length lower arms are preferable when the ultimate in strength is required and are often used in conjunction with adjustable upper arms to correct pinion angle. Heavy duty adjustable lowers can be used to aid in centralising the wheel in the arch on lifted vehicles, although there is a reduction in strength over the fixed-type arm.

Vehicles such as Nissan Patrols with a long-range tank fitted may require a bent upper control arm to allow for clearance from the tank when articulating. Quality bent upper arms are available in both fixed and adjustable configurations and will be dramatically stronger than factory. Another feature to look for when selecting a quality set of control arms is to make sure they come with high-quality rubber bushes pressed into the arms ready for fitment.

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Contact Superior Engineering

Phone: (07) 5433 1411
499 Uhlmann Road
Burpengary Queensland 4505
ASK THE EXPERTS: 4X4 Accessories and Suspension Tech Talk With Superior Engineering

© Copyright Superior Engineering

Date Published: 2014-03-22

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