The science behind Superflex arms-Superior Engineering

If you own a coil sprung Patrol or Landcruiser, you probably understand the versatility of the radius arm suspension platform and just how well they can handle most offroad conditions, they are one of the most popular OE link suspensions systems used in large solid axle 4wd’s.

This suspension uses two lower arms that attach from the frame down to the axle. This arm at the axle attaches itself both above and below the axle’s center line or in the case of a patrol/cruiser front and back. These attachment points keep the axle from twisting under the vehicle. In addition to these two links a panhard rod is also used. It attaches from the driver side frame down to the passenger side axle again using misalignment joints and or bushings. Its duty is to keep the axle centered under the vehicle from lateral forces.

  • Traits: Due to the use of a panhard bar a lower roll center is typical of this type of suspension when used in the front. Oversteer is also a common trait among lifted vehicles. The Instant Centre is located by the placing of the lower links at the frame; therefore radius arm suspensions typically have very high AS (Anti-Squat) numbers and are non-adjustable.
  • Advantage: Provides a very good pinion angle throughout its range of travel. Relatively easy to design/build and doesn’t have the complexity of the other systems.
  • Disadvantage: Steering suffers, in that the links don’t allow rotation of the axle in relation to the frame as the suspension cycles up and down, which cause caster changes. Wheel articulation is also limited due to link or bush binding, a problem that is inherent with this system. One wheel pushes up and the other drops, which cause the links to twist the housing along its axis, much like a torsion bar. Options to upgrade flex or handling are limited by OE link placement making it inherently difficult to fine-tune torsional characteristics (flex) or Anti-Squat / Anti dive.

As you can see from the photo, as torque increases on the front axle, the reaction forces try to pull down on the frame at the radius arm mount and try to compress the front coil springs. Now when all this happens somewhat quickly, instead of the frame being pull down towards the axle, the axle is lifted up towards the frame and loses traction with the ground. When traction decreases, torque also decreases and the axle falls back down and once again traction is restored and torque increases. This becomes a vicious cycle and causes the wheel to just bounce up and down and gains you little to no forward progress.

When it comes to improving offroad ability, there are a few key design objectives. Firstly, Drive-ability (handling/comfort & control) followed by – Stability, Ground Pressure AND Power Transfer.

The newly designed Superior Engineering – SuperFlex Arms are a blend of two different styles of arm, each complimenting the angles of deflection required for controlled flex. The key is to change the planes of deflection to allow full movement and resist the terrible binding and tearing of bushes that occurs. Another feature is the transmition of complimentary torque back into the chassis to reduce the sway that link (3,4or5) or pivoting/wristed radius arm setups produce. The ability to maintain excellent driveability is the key to success in the superflex radius arm system. The changes in bush type designation and orientation on the superflex arm allows dramatically increased controlled deformation. The adapter plate allows a change in bush position which provides a larger range of allowable flex before binding, whilst still providing adequate ‘feel’ back into the chassis. Typically as radius arms flex they subject the bushes to a converging load which tends to tear the bonding and cause premature failure, with the superflex arm, the bushes are mounted in a different plane (vertical) which has a much greater range of motion and therefore allows the suspension bushes to pivot with reduced restriction and less side loading, increasing component life. The arms themselves are also designed with accurate caster correction built into the design, alleviating any loads on the bushes, further increasing suspension life and aiding in correct steering geometry.

The Superior Engineering – SuperFlex Arms are all designed around a complete bolt-on setup and are available to suit suspension or lift sizes from 0” to 6”+. They are designed to maximise front suspension travel and are optimised to work with most long travel shocks and springs. The Arms comes ‘ready to fit’ with full OE style rubber bushes pressed in, Superflex-adapter plates as well as all the required bolts and fitting instructions and are currently available to suit a range of vehicles including Nissan Patrol –GQ & GU, Toyota LandCruiser 80/105, LandRover (wide bush) – Range Rover Classic, Defender, Discovery 1.

Another breakthrough in design is the Superior Engineering Hybrid Radius arms which are designed to combine the benefits of the Famous – Superflex Arm technology and the improved high-speed handling of a drop box style mounting. This allows the arms, the ability to soak up the bumps and keep the wheels planted without sacrificing maximum articulation that the Superflex arms can provide. With a keen eye on performance, Superior engineering has developed a drop box mounting for GU and GQ Patrols that is nearly 20% lower profile than any other on the market. This specially designed mount allows the Radius arms (standard or superflex) to be substantially longer than a factory arm which further aids articulation and handling. The rear arm bushing has also been upgraded to a radial type bush rather than the failure prone pin type mount.

All Superior Engineering Radius arms are Australian made and manufactured from premium Australian 350 grade steel then CNC machined for precise caster location. Even the logo is CNC machined to ensure you are getting a true quality component. All fabricated items are sand blasted and powder coated for maximum durability and the highest quality finish.

The ‘Superior Engineering Hybrid Radius arm’ kit comes ‘ready to fit’ with direct bolt-in drop boxes, full OE style rubber bushes pressed in and also all the required bolts and fitting instructions.

To suit lifts from 3” to 6” the Superior Engineering Hybrid Radius arms are available suit to GU and GQ Patrols in both Standard or Superflex arm configurations.

For more information call Superior Engineering

(07)5433 1411



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