Everything you need to know about 4x4 suspension.

We were invited down to Superior Engineering the other day to see the workshop. As the OE Ranger was copping a serious suspension upgrade, we took the chance to explain a few things we’ve picked up and some helpful information to anyone who might be curious. If you’re new to the 4x4 space or want a refresher on what everything means, then you’ve come to the right place.

GVM Upgrade?

First off we have to discuss GVM’s or Gross Vehicle Mass, which is the weight that marks the upper limits of what your vehicle can handle while still being able to perform safely on the road. This GVM is specific to each vehicle, with different vehicles being able to handle amounts of weight. This is a very important fact to consider when loading your vehicle with accessories such as bull bars, long-range fuel tanks, winches, and everything in-between. The only way to upgrade your GVM is to go to a professional to upgrade suspension components or sometimes even chassis reinforcement or brake upgrades. This ensures the vehicle will still operate safely while increasing its GVM.

What is IFS & IRS?

Now actually getting into the different types of suspension, the most common type used in most modern cars are IFS, independent front suspension, and IRS, independent rear suspension. Previous to this, solid axle suspension had been used for many years in vehicles such as your Y61 Patrols or 80 series Land cruisers but these have been fazed out due to the number of benefits IS offers such as better on-road handling and less unsprung weight.

Leaf Springs and Coil Springs?

In the rear of your vehicle there are two different types of suspension used- Leaf springs, which are most common in the rear end of Utes, allowing them to carry more load and Coil springs which are most common in the front end of most modern Utes, common in both the front and back of most modern wagons like the 200 series, Pajero, Isuzu MU-X etc.) and standard in the rear of NP300's which have a coil rear end with a multi-link suspension set up. Coil springs are a little less common than leaf springs due to their higher price, but they do give a smoother ride in most circumstances, making them a very popular choice among 4-wheel drivers.

What are Bushings in cars?

Bushings are found in all your moving arms and suspension pieces, allowing for play in your connections, and avoiding metal-to-metal contact. This prolongs the life of your equipment and makes the servicing of your suspension cheaper.

What are Remote Reservoirs?

The quickest bushings to wear out are usually found in your remote res. Remote res is short for the remote reservoir, a piece of equipment added to shock absorbers to allow for larger oil quantities in each shock. Originally used for suspension that was being worked consistently and at high speeds, it keeps the oil at a lower temperature which in turn allows for better overall performance and longevity. In modern-day applications, remote res shocks can have benefits for vehicles doing remote touring, especially when the shocks are being worked for long durations such as over corrugated roads.

What are Bump stops & Progressive Bump Stops?

Bump stops are used often in new suspension and are usually a solid rubber piece that stops the suspension from travelling past its desired range of motion, avoiding damage to the rest of the vehicle. Unfortunately, these Standard bump stops can often cause a harsh ride due with harder and sharper bumps when hitting them at speed. This can be helped by switching to progressive bump stops which replace the solid rubber piece for one with hollow potions, giving your suspension a progressive slow instead. This can then be taken to the next level with your hydraulic bump stops, which are often used in performance vehicles that are constantly hitting bumps at high speed.

What are Shackles on a leaf spring car?

Shackles refer to the connecting point between leaf suspension and your chassis.  There are a number of reasons that shackles are important to someone looking to optimise their suspension set-up, one of the most common reasons is to increase height without changing the leaf's themselves, allowing for more up travel in your suspension before reaching your bump stops.

What are Sway Bars?

Unless you’re a patrol or Landcruiser driver, sway bars are an important part of your vehicle, as they help stabilise your vehicle to avoid unwanted body roll, providing a more stable ride in the process. However, these can be a limiting factor when driving off-road which is why there are options such as less limiting sway bars, quick disconnects allowing for easy removal at the trail and connection after, or, in some cases, sway bars being removed entirely, but this is not ideal for driving on paved roads.

What is a Steering dampener?

Steering Dampeners protect your steering from forces being placed on the front of your vehicle that may cause loss of control. They eliminate any harsh bumps from hitting potholes or other small objects and also take a lot of strain off of other suspension and steering components, allowing for better longevity on components and bushings.

What is Castor & Camber?

Caster and camber go hand in hand with castor referring to the angle your wheel and in terms of suspension leaning forward and back and camber referring to the up and down angle. This can affect on-road handling and tire wear but is particularly troublesome with off-road applications. This mainly comes into play when we're talking big lifts such as 3 inches and over. Castor begins to play a factor, particularly with your solid front axle cares. As the diff moves through its range of motion the caster will move too far into a positive or negative position. In this case, castor correction plates and bushes can be installed to correct this and take some strain off your suspension and tires.

What are Airbags?

Airbags have become popular for several reasons. Airbags are often placed in the rear suspension of the vehicle either inside a coil or in between the leaf spring and the chassis. The main one of which being able to inflate the airbag to a high PSI to stiffen the suspension. This is helpful when carrying larger loads when loaded up for a trip or towing heavy loads. This then allows for lightweight leaf or coil springs to be run most of the time.

What are Extended Brake Lines?

Extended brake lines pretty much do what the name implies and are installed when a large lift is installed as the brake lines are now required to travel a larger distance practically when in a dropped range of motion.

This is just a brief overview of everything you need to know when thinking about doing suspension modifications to your 4WD. There are many different things to consider before tinkering around underneath a vehicle. Make sure you always install upgrades that are vehicle specific and never perform work on your own car unless you are 100% certain you know what you are doing. Consulting a professional is always a smart move, as road safety is the most important aspect of owning a vehicle.