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4WD Suspension Selection Guide – Avoiding Problems

4WD Suspension Selection

 

4WD suspension selection is very important.

When I upgraded the suspension as part of my 4WD build it was the single biggest change I had made to the car, with the entire driving experience changing instantly for the better.

But there are ways you can ruin your car with poorly selected suspension, specifically the springs.

In this post I want to touch on 4WD suspension selection in general, focusing on the standard 2 inch lift for dual cab utes with leaf springs at the rear and IFS (independent front suspension) at the front.

This is meant as a general guide to point out some potential issues that can go wrong with poor 4WD suspension selection and my experience installing new suspension from Outback Armour.

This is not meant to be an in-depth guide to massive lifts for competition trucks, but for those with standard cars looking for the little bit of extra lift and driving performance while staying road legal.

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Why upgrade the suspension?

 

The main reason to upgrade your suspension is because you have added permanent weight to the car through accessories such as: bull bars, spotlights, water tanks, long range fuel tanks, canopies etc.

A ute is made to take a heavy load at the rear, this is why they mostly have leaf springs (Navaras don’t for example), the tub at the back is meant for carrying heavy loads and often the utes will actually perform better on the road with 100-300kg on the back.

This weight is sometimes not as simple as material that gets put in and taken out, it is often permanent in the form of accessories, which can easily add up to 500+ kilograms on some vehicles when loaded for a trip.

So the three things we want to rectify with all this extra weight are:

 

Performance

The way the car behaves on and off the road is the major issue here. As I added weight to my car it sat very low, it wallowed around corners with lots of roll, it was slow to accelerate and braking performance was not very good as the car did not sit firm.

After changing to correctly weighted springs front and rear, with much better shocks, the change was phenomenal on the road. Off the road it is even better as the tyres spend more time in contact with the road, which means it rides more safely and confidently.

 

Ride height

This is linked to the performance of the car when offroad. A lot of people change the suspension for that extra lift regardless of if they have extra weight or not on the car.

What this does is improve the approach, ramp-over and departure angles of the car when off-roading.

It can also give you better vision to see the path ahead as you sit taller on the track.

Raising the suspension will lift most of the car, but it will not change the height of your diffs for example which are unsprung components of the car, but it will still get most of the car higher to reduce chances of bellying out in sand or ruts.

 

Reliability

The added benefit from all of this is that with the larger shock absorbers that come with after market suspension setups allow more oil to be held in the shock, which means it handles heat better.

These new shocks will perform much better in rough conditions, keeping the tyres on the road, staying cooler and being able to handle more unsprung weights reliably, such as larger than normal tyres.

What suspension to buy?

 

I can’t really help here as there are multiple brands on offer with a similar range of products. Without having tried them all I can’t comment on their quality.

All I can say is that I went for Outback Armour Adjustable Bypass suspension (Outback Equipment link).

I will go into more detail about the part numbers and prices further down the post, but the reason I chose them was based on word of mouth from people who install suspension and say that they never get warranty call backs for them.

I also knew two people who had it on their cars who couldn’t complain, although the price I paid was a lot higher than they paid because they have become very popular now thanks to their reputation.

 

Front Suspension

 

In this section I’ll be discussing the 4WD suspension selection for an IFS vehicle, suspension is a complicated subject and an endless rabbit hole so I don’t have time to cover every minor detail.

The principle of selecting the right suspension based on weight remains the same for IFS or solid axle, but the issues of getting it wrong can differ.

IFS 4WD suspension selection process

 

There are a few different things to consider when buying suspension when it comes to the style of shock absorber you want to get, but before you get to that you will need to select the correctly weighted springs.

After that you will need to decide what style of shock absorber suits your needs, but I can’t help you there, however I will explain what I bought and why.

Choosing the correct springs

 

For this step you need to decide what the final weight of your car will be. This is obviously easier if everything is already installed, otherwise write out what you plan on getting installed.

For me, I was able to wait until it was all installed and I came up with the following weights because I weighed everything as I built the car.

 

Given the above weight total of ~140kg I knew that I needed to go with a spring to suit.

But I recommend never going over sprung!

Using Outback Armour as an example I had 3 choices of springs which were:

  1. Trail = 50mm approx lift (unladen).
  2. Expedition = 50mm approx lift (@ 50-100kg load).
  3. Expedition HD = 50mm approx lift (@ 100-150kg load).

Looking at these numbers, if you calculated 100-110kg load at the front, my recommendation would be to under-spring the car and go for the Expedition kit here.

There are a few reasons I suggest this, I personally even considered going for the Expedition kit even though I was at 140kgs or thereabouts.

However when I looked deeper into it I noticed that the only difference between the two was the way that Outback Armour sent it to you via the adjustable threaded seat that you see below. 

 

This adjustment allows you to change the height of the ride (marginally, not endlessly) to rectify any issues with ride height, so I decided to go for the Expedition HD instead knowing I could always lower the ride height if needed later.

Issues with not choosing the right springs

 

If you get the wrong springs and over-spring the vehicle it will lift more than its advertised amount. This is something to be mindful of if you’re buying springs early but haven’t yet installed your bull bar and winch for example.

There are a number of issues that arise when we over lift the vehicle ranging from reliability issues, performance issues, cost increases and even legal issues.

The 2 inch lift is generally considered the ideal lift for most people who are using the 4WD on anything but very tough tracks. It is therefore my recommendation for over 90% of people in the 4WD suspension selection process to stop at 2 inches.

CV angles

 

The CV joint on IFS vehicles is meant to operate at a mostly straight angle, but see below how this angle changed before and after lifting the car by switching between the two photos.

 

This is a major reliability issue, if you go off-road and experience wheel lift at the front you’re quite likely to break the CV joint which is not a fun fix track side.

This also introduces a lot of cost to try and counteract this issue from arising.

A diff drop kit will cost anywhere from $400-600 and can affect bash plate fitting, resulting in more costs.

 

Wheel alignments

 

If you over-spring the car you will not be able to get a wheel alignment done properly as the range of adjustment in your upper control arm will run out.

This is another extra cost that can be anywhere from $700-900!

The correctly rated springs will give you just the right amount of lift so that you can still get a proper wheel alignment without needing to go buy adjustable UCAs, which is why it’s important to select the correct springs for your weight.

Without a proper alignment you will chew through your tyres much faster resulting in even more costs.

Performance & legality

 

If the car is over-sprung it will not ride well, it will be stiff and sitting higher than normal which is not always good when off-road as it moves the centre of gravity higher.

On the legal side, this depends on state laws on how much higher your car can go from factory. This is a combination of ride height changes from tyres and suspension.

So 4WD suspension selection can affect you in a lot of ways, including whether the car is insured properly. An insurance company could argue the suspension made the car behave poorly and was not legal at the time of an incident for example.

Choosing your shock absorbers

 

Once you have got the weights down, it is time to choose the shock absorbers. This is really up to personal preference and this is where you need to consider what style of driving you do.

Do you drive remotely on corrugated roads? Maybe get remote reservoir shocks.

Do you have changing loads? Consider adjustable bypass shocks.

Do you want to set and forget? Get the upgraded shock size without the extra features.

As there are so many variables here I won’t go into too much detail but I will briefly touch on what I purchased and why.

Why I bought an adjustable bypass assembled kit

 

I bought the adjustable bypass kit for one major reason.

It wasn’t that much more expensive and it gave me flexibility to change the ride for the next 100,000kms+ without needing to take apart the front strut assembly again.

It was just easier for me in the long run, but in saying that 80% of people who buy these adjustable bypass shocks never adjust them from centre anyway, so most could probably go with the standard offering.

Adjustable bypass basically means you can adjust the ride to be stiffer for more control, or to roll more for added comfort.

On the front of the car it is not as essential as the load does not vary like the rear of the car does with fuel, water, storage etc. However it is a nice feature to have for differing driving conditions.

The reason I went for an assembled kit is because it was easier and I didn’t want to reuse my existing upper strut mounts, nor compress the springs to get them on.

It saves time on install and I know that the strut mounts are brand new as well now.

The adjustable bypass was also the only offering by Outback Armour that included the threaded adjustable spring seat which I wanted to have in case I needed to lower the ride height to avoid the issues mentioned above. 

 

Rear Suspension

 

In this section I’ll be discussing the 4WD suspension selection for a leaf sprung vehicle, which is the most common type of suspension across the ute market.

Leaf springs are often used as they’re capable of taking a very large amount of load with relative ease.

Because these cars are utes, they are made to take a variable amount of load in the back, but you can get them to drive much better by upgrading the leaf pack to suit the permanent or planned majority load amount.

Leaf spring 4WD suspension selection process

 

This is exactly the same as the process for the front but with a few different issues that arise from getting it wrong. We start with the spring and all of our expected weights.

Choosing the correct springs

 

With the rear of the car the weights can change a lot more than the front. If you have spend the majority of your time at full load (water, luggage, diesel, canopy, groceries) and less time around town, you may want to select for this majority weight.

For me, I just weighed the permanent stuff and selected for that, which gave me the following results.

Using Outback Armour as an example I had 4 choices of  leaf springs which were:

  1. Trail = 40mm approx lift (unladen).
  2. Expedition = 40mm approx lift (@ 150kg load).
  3. Expedition HD = 40mm approx lift (@ 300kg load).
  4. Expedition XHD = 40mm approx lift (@ 500kg load).

Given the above weight total of ~357kg I was sitting in between two popular spring rates, that of the constant 300kg leaf and the 500kg leaf pack.

Although when I added water, a long range fuel tank, luggage, food etc I would be closer to or over the 500kg limit, I decided to install the constant 300kg leaf springs instead.

The reason for this was because I would be spending more time at 350kg than I would over 500kg and I wanted the car to drive better during those times.

The car will be fine to take on more load, that’s what leaf springs are for, but I wanted the best ride as possible as well as to avoid the issues that arise from poor 4WD suspension selection at the rear.

Issues with not choosing the right springs

 

If you get the wrong springs and over-spring the vehicle it will lift more than its advertised amount. This is something to be mindful of if you’re buying springs early but haven’t yet installed a canopy or water tank yet for example.

The manufacturer’s will try and give you a maximum lift at the rear without upsetting the driveline balance.

For the model of car that I have (but also with others) driveline vibrations can occur from having the car lifted too much and not correcting the centre bearing angles.

The other thing that can occur is the shock absorber will exceed its recommended CWG (centre wheel to guard) measurement.

Centre bearing angles

 

In a two piece tail shaft there is a centre bearing, this angle should be dead straight and when it isn’t there can be vibrations through the car at certain speeds.

See the comparison images below from pre-lift, post-lift without spacers and post-lift with spacers installed.

 

This can be very difficult to fix if the springs are too much, even with a spacer kit.

Outback armour include a spacer kit for the Mazda BT-50 / Ford Ranger suspension kits as it is a common problem on these cars, luckily mine was good after the spacer kit was installed.

 

Performance & legality

 

As with the front suspension, if the spring is poorly married to the weight in the car it will be stiff and ride poorly, excessive lift could also result in the car being technically illegal.

Choosing your shock absorbers

 

Once you have got the weights down, it is time to choose the shock absorbers. This is really up to personal preference and this is where you need to consider what style of driving you do.

Do you drive remotely on corrugated roads? Maybe get remote reservoir shocks.

Do you have changing loads? Consider adjustable bypass shocks.

Do you tow? Might want to look into airbags to assist on the rear.

As there are so many variables here I won’t go into too much detail but I will briefly touch on what I purchased and why.

Why I bought an adjustable bypass rear shock

 

With the rear suspension often having a changing load to account for I was always going to get an adjustable bypass style of suspension.

This gives me full control over the stiffness at the back as weight is added for specific trips and then being able to revert to the most comfort when on the road.

As I don’t tow I don’t see any need for airbag suspension, nor do I see the need for remote reservoir suspension. This to me was the right balance of adjustability without going overboard with he most expensive kits available.

4WD Suspension Install

 

I have the following video which goes into 4WD suspension selection as well as the install process. Obviously this is specific to my car and the suspension I installed, but there may be tips in there that help you do your suspension. 

Changes to ride height

 

It is important to note that the changes that you will see in your ride height will be more than is advertised.

This is because the advertised height changes are for that particular spring setup with an advertised weight compared to the factory ride height with no weight at all.

Because your car will either have weight (factory suspension already compressed) or won’t have the weight yet (aftermarket suspension then provides extra lift) the results will not be a 50mm or 40mm change.

This of course changes if you choose the spring for unladen setups, in which case you should see close to the advertised change in ride heights.

My front suspension measurements

 

I have had the following CWG measurements:

  • 546mm = pre-lift.
  • 612mm = post-lift.
  • 608mm = post-lift plus ~1,000kms driven.

So after settling a bit I saw a lift of 62mm, however take this with a grain of salt because I had already changes one side of the car before I remembered to measure it, so the lift from the compressed factory state would actually have been higher than this.

My rear suspension measurements

 

I have had the following CWG measurements:

  • 505mm = pre-lift.
  • 620mm = post-lift.
  • 614mm = post-lift plus ~1,000kms driven.

So after settling a bit I saw a lift of 109mm.

This just goes to show how far the factory suspension sits down when it has 350kg applied to it. This can be seen in this guidance chart from Outback Armour.

Bump stops

 

Do you need to change the bump stops? No.

However they are inexpensive, and if you’re going to have the car apart, as well as be adding weight to the car, then bump stops are a quick and easy install that can improve the ride.

How the bump stops from Outback Armour work is simple, they’re progressive. 

Being larger, they engage earlier and result in less of a thump when the limit is reached, giving the car greater control and the passengers greater comfort when maxing out the suspension through pot holes for example.

You can see how the after market bump stop has a longer rubber section, this is softer at the top and harder as it compresses so the shock and thump is reduced to the car.

The image is of the front bump stops but I also did the rear bump stops as well.

Weight increase

 

Adding after market suspension will add quite a bit of weight to the car. All of the parts are made from thicker materials and are larger in size as well.

I was surprised at how much weight was added in things like the rear shocks alone, with each rear shock being almost twice as heavy as the OEM shock.

I added the following weights to the car:

  • 1.21 kg – Leaf spring shackles.
  • 0.46 kg – Bump stops front and rear.
  • 3.41 kg – Per front assembly (6.82 total).
  • 5.08 kg – Per leaf spring (10.16 total).
  • 2.02 kg – Per rear shock (4.04 total).
  • 22.846 kg TOTAL WEIGHT ADDED.

I knew it would be heavier but for some reason that number surprised me.

Cost

 

Living in WA things are more expensive normally due to freight, but I was able to pick these up for $3,000 through Medicar (fitted myself) who included all the bump stops and shipping in the cost.

The advertised price for all those components is ~$3,200 but they have increased a lot the past few years due to their reputation and popularity.

Conclusion

 

That’s it for this post, just wanted to highlight the possible damages and issues that can occur from selecting the wrong weight for your 4WD suspension selection process and briefly touch on what I chose and why.

There are plenty of good brands besides Outback Armour out there and the install is not too hard with proper instruction and tools.

Check out the video for install hints and good luck with choosing a good suspension setup for your rig!

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