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The Science Behind Superflex Arms

PATENT NO. 2008202797
PATENT NO. 2010100451
PATENT NO. 2011904187

by Superior Engineering

Michael Hayes reveals and explains the science behind Superflex arms.

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 centre 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 centred under the vehicle from lateral forces.

As torque increases on the front axle, the reaction forces try to pull down on the frame.
Figure 1. As torque increases on the front axle, the reaction forces try to pull down on the frame.
  • 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.

SuperFlex Arms

PATENT NO. 2008202797
PATENT NO. 2010100451
PATENT NO. 2011904187

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 transmission of complimentary torque back into the chassis to reduce the sway that link (3, 4 or 5) 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 adaptor 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 on (07) 5433 1411.

Superior Engineering Super Flex Arm Features

Super Flex Arm Features and Benefits
We use only use standard Nissan bushes We use only use standard Nissan bushes, allowing purchase of bushes anywhere. The plates are zinc coated The plates are zinc coated hard wearing, rust resistant coating.
New high tensile 8.8 Grade bolts New high tensile 8.8 Grade bolts supplied with all Superior arms, Both passenger and drivers side. Authentic Superior Engineering Logo Authentic Superior Engineering Logo CNC machined into the side of the arms, so you know you have purchased a genuine product
All Superior arms are made from 32mm 350 Grade steel plate All Superior arms are made from 32mm bissalloy 80 / 700 grade steel plate for strength and laser cut for precision. Arms are a hard silver powder coat All Superior's arms are a hard silver powder coat, to resist damage to the finish.
Arm blanks are CNC machined for repeatable accuracy Arm blanks are CNC machined for repeatable accuracy. Threaded end is cut on a CNC lathe The threaded end is cut on a CNC lathe to ensure a perfect fit every time.
Super flex plates are laser cut from 10mm steel Superiors Super flex plates are laser cut from 10mm steel, and feature the laser etched Superior Engineering Logo. All weld are carried out by certified welders All weld are carried out by certified welders to the highest standard.

Nissan Logo

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Toyota Logo

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Landrover Logo

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Nissan Patrol GU

STD Height
2" Lift
3" Lift
4" Lift
5" Lift
6" Lift

Nissan Patrol GQ

STD Height
2" Lift
3" Lift
4" Lift
5" Lift
6" Lift

Toyota Landcruiser 80/105 Series

STD Height
2" Lift
3" Lift
4" Lift
5" Lift
6" Lift

Toyota Landcruiser 76/78/79 Series

STD Height
2" Lift
3" Lift
4" Lift
5" Lift
6" Lift

Landrover Discovery 1 & Defender

STD to 2"



Superior Engineering has now added a new product to our Super Flex Arms!! The single passenger side Super Flex Arm that is for use with our Drop Boxes. We all know that you can't beat the driving quality of Superior Drop Boxes and who doesn't want more flex out of a 4wd providing it still retains the same on road handling. This is where Superior Engineering came up with the great new idea to combine Drop Boxes and Super Flex Arms together to create the best of both worlds.

The GU wagon pictured here is using 350 lbs rear coils and 315 lbs front coils, it tows a car trailer with the Team DGR Nissan to competitions as well as being an every day driven vehicle. As you can see it certainly does not lack flex in the front end considering how thick the coils are, remember that the front bullbar is alloy, and it is only a petrol engine without a second battery. If you already are lucky enough to be one of many thousands of 4wders with Superior Drop Boxes than why not take you 4wd to the next level!


Below are some helpful forum links that discuss these "Superflex Flex Arms"








Watch a Video on Superflex Radius Arms

Benefits of Superior Engineering SUPERFLEX Drop Radius Arms

  • Manufactured from bissalloy 80 / 700 grade steel
  • High Tensile 20MNV6 Bush Eyes
  • Massive 32mm main Beam thickness for maximum strength
  • Rubber Bushes pre-fitted into arms
  • Laser cut to precise measurement and caster location
  • Authentic Superior Engineering Logo machined into side of Arms
  • (Factory Sway bar will fit to allow safe on road handling)
  • The Brackets to fit the sway bar and extensions are supplied at no extra cost
  • They are manufactured to suit various lifts
  • Sand blasted with rust prevention applied
  • Powder Coated for maximum durability and finish
  • 350 grade steel will not crack unlike Cast Radius Arms
  • Adapter plates and bolts have a SA5 Zinc coating for rust prevention
  • Allows vehicle to track correctly on road due to correct caster
  • Maximum Clearance between the Tie Rod and the Radius Arms
  • Factory bushes fit the SUPERFLEX ARMS, We don't use special sizes Bushes
  • Superior Engineering's Super flex arms are a Patented Design
  • Patent No's. 2008202797, 2010100451, 2011904187
  • 100% money back Guarantee if you don't get more flex than your original or aftermarket Radius Arms!

Development Test Document

Superior Engineering Superflex Arms - Suit Toyota Landcruiser

Test criteria: Stock 80 series w/ HD 3" lift open diffs, sway bars and OME shocks.

Test regime: Performed on a 30 deree ramp with front shocks removed to allow comparative measurements across the front shock mounting surfaces.

Tests performed:

  1. Swaybars attached F&R, STD radius arm configuration
  2. Front swaybar disconnected, rear swaybar connected, STD radius arm configuration
  3. Front swaybar disconnected, rear swaybar connected, STD radius arm configuration with front bolt removed on Passenger side (to simulate 3link/X-link max flex)
  4. Front swaybar disconnected, rear swaybar connected, New SuperiorEngeering Superflex radius arm installed.
  5. RTI calculation - (configuration as per #4) 30 degree ramp driven forward and reverse directions.
TEST 1 543 640 97 3" STD + SWAYBARS F&R
TEST 2 505 660 155 3" STD + SWAYBAR REAR

Note: OME shocks to suit specified lift = 710mm ext, 480mm comp, 230mm travel.

TEST 5 - RTI as calculated, 2850mm wheelbase. (config #4) Superflex arm fitted, rear swaybar connected.

Distance travelled FORWARD - 1795mm = 909 RTI @ 20degree (622 RTI @ 30degree)

Distance travelled REVERSE - 1690mm

Supplementary Testing:

A further set of tests were performed in which to acquire data for the optimisation &/or replacement of shocks and springs to create 'a full package'. The testing involved removing front and rear shocks so as not to pollute the data and allow access to measure the available travel of both front and rear suspensions, this also allows us to measure the useful travel of the vehicle setup as a whole.



RTI - (distance as measured on 30 degree ramp)

Forward - 1830mm = 940 RTI @ 20degree (642 RTI @ 30degree)

Reverse - 2065mm


Overall flex direct comparisons (test#2 - test#4) show a huge improvement in front end flex, with useable travel increasing from 155mm to 235mm+ as measured at the shock position. This amount of flex (230mm+) is equal to or greater than the maximum shock travel as offered by most OE manufacturers. Test #5 was performed as an indicator of overall component integration, and the maximum constraints of standard suspension components. Continued testing and development is recommended to attain the better commercially available shock and spring alternatives.

So for the first time a good bolt-in solution is offered that can finally use ALL of the available shock travel in most 'long-travel' lift kits!

Contact Superior Engineering

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