The importance of 4WD Suspension
4WD Suspension plays a major role in how your four wheel drive handles, how capable it is and how comfortable you are; taking the time to find a suspension kit that suits your vehicle is vital. A lot of people spend big dollars on kits only to find they are uncomfortable and don’t do what they want them to. By spending a bit of time reading this you can make a better educated decision!
What does Suspension do?
Suspension is designed to absorb bumps, keep wheels on the ground and improve handling. When you hit a bump, the suspension absorbs it, rather than passing it through the car to where you sit. Suspension that is set up incorrectly (or that is worn out) severely limits your ability to control a vehicle and it is much more uncomfortable!
It is also designed to keep your four wheel drive body level (whilst the chassis and differentials move in and out of the bumps).
Components of 4WD Suspension
Most Suspension kits are made up of shock absorbers, springs and linkages, although there are a myriad of different set up’s for different purposes.
Contrary to belief, shock absorbers do not stop the bumps. They are there to stop the spring from bouncing up and down (to absorb the shock). If you get a soft spring and make it move in and out, it will keep moving for a long time.
However, if you attach a shock absorber it will stop almost immediately. When you are driving a modern car you will notice that a bump causes your car to go up and down usually once, but no more. This is because the shock absorbers stop the continual bouncing. Shock absorbers are extremely important!
The springs in your 4×4 Suspension take the weight that you are carrying, and are designed to take the impact of uneven roads. Without shock absorbers your vehicle would bounce up and down all the way down the road.
Types of 4WD Suspension
There are a number of different types of 4×4 Suspension. However, it is always split into two categories – solid axle and independent suspension. The more common types of 4×4 Suspension within these two categories are coil springs, leaf springs, coil overs, multi link and the list goes on!
Solid axle suspension
Solid axle suspension refers to the suspension on either side of a differential being connected together. When one wheel goes down, the other is forced up. When you hit a bump on the left side, you will feel it on the right side. The general consensus is for serious four wheel driving and for fitting large lift kits and bigger tyres solid axles are better. They have a much better range of flex and they tend to be stronger.
Independent Suspension is known as IFS or IRS (Independent front suspension and Independent rear suspension). The obvious difference is that the suspension on a differential is not connected together. The left side can go up or down without anything happening to the right side (and vice versa!).
The limitations though, are that you can’t lift it more than 2 inch very easily, the flex is often very limited and they tend not to be as strong. However, they do offer better clearance, and are much more comfortable on road. It is a compromise either way.
Solid axle or Independent Suspension – what is better?
The more modern four wheel drives today are favoring independent suspension, which seems to limit the modifications that can be done and the places you can take the four wheel drive. Don’t get me wrong, independent suspension is your best option for comfort providing you aren’t intending on running much larger tyres or a lift kit beyond 2”.
If you intend on running large tyres, a bigger lift kit and you want flex, solid axles are the way to go. The only independent suspension that really works on a four wheel drive is found on a Hummer – but they have a very unique set up!
How long does it last?
Suspension should be checked regularly. The time it takes to wear a set of suspension out very much depends on the driving you are doing. Driving on heavy corrugations regularly will wear your suspension out much faster than if you never leave the black top. Springs are usually obvious when they are worn, but shock absorbers may not be so much. It pays to get your suspension checked regularly, to ensure it is still safe and performing correctly. Some things can easily be changed – rubber bushes for example. You will hear the springs start to squeak when these wear out!
Fitting 4×4 Lift Kits
If you are really into four wheel driving, there is a good chance that you have looked into lifting your vehicle. 4×4 Lift Kits are a great way to get more clearance, better flex and a more reliable and capable suspension system.
However, please ensure you do plenty of research before adding one, as there may be more to it than you realize. Check the legalities – if you add a lift that is too big then you void your insurance. Suspension lifts greater than 2” often require different sway bars, panhard rods, steering dampeners and extended lines (brake lines, breathers, etc).
Important factors of suspension
4×4 Suspension has a wide range of factors that need to be considered. By making sure you think about each and every one of them, you will get the best results. Remember though, that suspension is often a compromise, one way or another. I’ve made a quick list below:
Weight carrying ability
The amount of weight that you carry in your four wheel drive needs to be seriously considered. A lot of people recommend getting everything that is heavy fitted to your four wheel drive before you do any suspension modifications (such as bull bars, rear bars, tyre carriers, dual fuel tanks that are full of fuel, roof racks, fridges and other heavy items inside the vehicle, water storage etc).
If you carry a lot of weight in your four wheel drive, you need suspension that is going to sit level and handle the weight correctly. Unfortunately though, when you remove that weight, your vehicle won’t be as comfortable to drive around. There really isn’t much that you can do to avoid this, unless you get Air Bags – see further below.
Fitting suspension that is going to carry the load that you want to safely is the most common problems in four wheel drives. If you get springs that are too stiff you will have a back breaking ride when it is empty. Seriously take the time to think about what weights you are carrying, and discuss this with your suspension shop.
Flex refers to the amount of travel your wheels have. This is extremely important for more serious four wheel driving, as it determines whether your wheel sits on the ground (and thus whether you have traction) or whether it is left hanging in the air. It also determines how much your vehicle tilts. 4WD’s with massive flex are able to drive through huge offset ruts without the body of the car tipping too much. If you have limited flex though, the body tends to move over the chassis, which can be dangerous.
The primary reason for suspension is to improve comfort. If you have driven in an older vehicle, you would know that suspension plays a massive role in keeping people comfortable. Do what you can to get a kit that is going to keep you comfortable. There is nothing worse than arriving at your destination with a back so saw that you can’t walk!
You want to get 4×4 Suspension that is going to last. One of the most common examples given is heavily corrugated gravel roads. Take a cheap shock absorber and an expensive, heavy duty one and compare them. Shock absorbers are designed to stop the springs moving up and down, and this causes a lot of friction inside the shock absorber. This in turn becomes heat. After driving along a road where your suspension takes a beating, get out and put your hand near the shock absorber. It will likely be very hot!
In the Australian bush, cheap shock absorbers will heat up very quickly when they are being worked hard, and they will literally fail due to excess heat. If you are doing heavy four wheel driving, you need heavy duty shock absorbers. You will know the difference when you compare the width of shock absorbers for the same vehicle.
As mentioned above, consider the terrain that you most often drive on. If you never take your four wheel drive off the road (I feel sorry for you!) then you probably won’t need to get heavy duty suspension. However, if you spend every day on gravel roads you are going to want some of the most heavy duty suspension available.
Improving your flex
People spend massive amounts of money improving the flex on their 4×4 Suspension. If you want to improve your flex, the first thing you need to do is determine what is limiting it. Many times the shock absorber is the first thing to limit your suspension, because the springs flex more than the shock. By getting longer shock absorbers, you may just find that you get much better flex.
However, this can create another problem. If you have coil springs, they can fall out when one wheel drops significantly as there is now nothing to limit the flex. Make sure you adjust your bump stops accordingly! Springs that are very stiff tend to flex much less, but if you need the weight carrying ability there isn’t much else you can do.
4WD Air Bag Suspension
One of the major problems with 4×4 Suspension is whatever kit you get, it isn’t going to do everything. You can’t get a kit that is comfortable with no load, but that doesn’t sag when you really load it up. Or can you? Suspension comes in a number of forms, and is usually set up based on the weight that you want to carry. The problem with suspension is that if you do fit soft springs you aren’t able to carry weight very easily.
Air Bags are a reasonably expensive (but well worth it in many cases) addition to your four wheel drive. They are literally little bags that can be inflated when you add weight to the vehicle. This ensures that your ride is still comfortable, as well as level. A saggy rear isn’t good for your vehicle, and it certainly doesn’t look good either! The alternative to air bag suspension is to fit larger springs in the rear than at the front, but this means your vehicle tilts forward when you have no weight in the back!
I’m going to put a note in here which I think people need to consider more; Dual cab utes in particular are very vulnerable to bent chassis when airbags are used. If you think about it, when you add an airbag to a vehicle with coil springs, the weight is still distributed over the 2 factory spring mounts. When you add air bags to a vehicle with leaf springs, you take the weight off the 4 load bearing points designed from the factory (where the spring attach to the chassis) and you take the weight in the middle of the springs, creating a pivot point on a location that was never intended to take weight. Google ute bent chassis, and you will be in for some scary photos. This happens considerably more than you might realise. Take care!
Buying the right 4×4 suspension
As you have probably gathered, there is a lot to consider when it comes to 4×4 Suspension. You don’t need to know it all, but it pays to have a rough idea. When you go to a suspension shop, you are relying on their expertise and you need to make sure they know what they are doing. If they don’t ask what sort of driving you do and what weight you are carrying regularly, walk away. A quality suspension shop will spend some time finding the perfect kit to suit you!
What brands are good?
Some of the more reputable brands for four wheel drive suspension are Kings, Fox, Old Man Emu (OME), Tough Dog, Rancho, Dobinsons, Monroe, Bilstein, Lovells and the list goes on. My suggestion would be to look on the 4WD Forums to find what other people have done with an identical vehicle to what you have. Certain vehicles will go very well with a set shock absorber and spring length, and you may as well make use of what other people have learned.
You are very welcome.
All the best
Thanks for the detailed explanation of suspension my son was curious about how they work. It was a very educational read
It’s good to know that suspension absorbs bumps and keeps the body level. I’m looking to upgrade my 4Runner’s suspension so I can take it off-roading this summer. Thanks for the tips and I’ll have to find a place where they can increase my suspension for my 4WD.