JMACX GVM and Coil Conversions

JMACX Off-Road Solutions

Is an Australian Manufacturing Business. Excelling in Engineered Solutions to build your ultimate vehicle. JMACX was originally founded by Jason McIntosh who was disappointed in his own 76 Series Wagon Landcruiser that had Leaf Suspension, after coming from a vehicle with all round coil springs he thought to himself why could the 70series not be the same. Being in the industry and a background in engineering Jason buried himself in the workshop and got into some serious Research and Development work.
From that Research and Development the worlds first ever bolt in coil conversion for a 70series  was created bringing ride comfort and more off-road capability to one of the most iconic vehicle platforms available, But Jason didn’t just stop there with a Full SSM Approval backing all of his coil conversion meant that not only are all of Jmacx products full approved with engineering for PRE and POST REGO Vehicles , but Jmacx could also bring you Australia’s largest GVM increases with the appropriate axle load ratings for the VDJ land cruiser range. Now today with hundreds of conversions done and millions of combined kms driven in some of the worlds harshest condition these kits have proven to go above and beyond and become the worlds number 1 coil conversion kit.
When it came to choosing and engineering a replacement rear suspension system for the 70 series Landcruiser there was a few different geometry’s to build off but only one was superior from all of them and this was the 5 link set-up.
The 5 link suspension system has been used by all Major vehicle companies for many years now for example 80/100/105 series landcruiser , Nissan NP300 and Patrol GQ/GU , Dodge Ram , meaning it has been tested and proven itself as a capable geometry set-up . The biggest advantage to the 5 link suspension set-up is its load carrying ability from the REAR PANHARD ( the 5th link ) this allows the rear differential to stay fixed and stabilised when cornering or with any side load on the vehicle , without this rear Panhard the differential would be able to move freely side to side from the chassis this would be suitable for light vehicles with low centre of gravity , rock crawling 4wd or a drag car that needs to only go in a straight line .
However when it comes to a heavy load carrying vehicle this would not be safe as it would not be able to support the side load on the suspension set-up hence where the 5 link came out on top. The 70 series is a load carrying vehicle with a high centre of gravity so the rear Panhard is a must to keep the suspension centred.

The 4 link Suspension system was another common geometry set-up that we looked at in the beginning however it had some major draw backs when it came to applying it on a 70 series land cruiser. Here is why Referencing straight from the
BOSCH Automotive Engineering Handbook Version 7 – 9 on what is needed”
‘’The basis of what is considered appropriate is based upon stability and other kinematic effects on the road handling of the vehicle.
4 link suspension system are acceptable in the correct circumstances and with the correct application of the engineering to ensure stability of the systems.The basic 4 link suspension system is designed for certain applications which are generally of high articulation applications ( Rock Crawling off-road vehicles , high monster truck types, performance cars , hotrods or very rigid suspension applications).
The following are the critical design aspects for 4 link systems.

  • Link lengths
  • Instant center (intersection point)
  • Anti-squat geometry percentage
  • Axle angle change
Note: Intersection Point is a very important aspect and provides the balance to the system.
With regards to running the 4 link setup on a 70 series land cruiser, it is not possible to run triangulated lower control arms as the diff centre is not centralised meaning you will have to use straight lower control arms this setup is far from ideal for a road going vehicle. The system should ideally be a double triangulated setup with both upper and lower control arms at opposing angels to ensure that the system can be centered at all times.
With a straight lower control arm, the axle housing is able to laterally traverse under heavy load cornering, or indeed towing (ie: will try and maintain its original track and then dynamically release to follow the vehicle and as such causes a significant amount of instability and can be catastrophic if coupled with a incorrectly loaded trailer ).
The images provided are considered an appropriate system with a double triangulated setup,

Looking for a GVM upgrade for your vehicle?
Landcruisers are not the only vehicles to spark our interest. Stay tuned to our social media for any upcoming product we may have for other vehicle makes as we are constantly developing products that are outside the box.