LAZY LOADING: How packing your ute (badly) can be disastrous
It’s very tempting to throw everything in the back of your ute without a care. But here’s why loading your ute the wrong way can lead to disastrous consequences out there on the road, and how you can load up safely…
Loading up your ute and hammering off into the sunrise can feel purposeful and liberating as you launch into another day of work, rest or play.
But in a dual cab ute where the rear wheels are essentially right at the front of the load space, at the back of the cabin, lazy loading can have devastating consequences in the wrong circumstances.
In this report we’re going to look at how lazy loading happens, why it’s a calamity waiting in the wings with a possible encore from the Grim Reaper, and we’ll look at real solutions to avoid it in the future.
Let’s start by defining the phenomenon of ‘lazy loading’. Imagine you’ve got a big pile of stuff (payload) to get into your ute for whatever scenario. It might be holiday packing for the family to head away for Easter long weekend, it could be a small mountain of building supplies for the jobsite, or it could be some kind of simple, but heavy and awkward hauling assignment like a pallet of pelletised chook poo.
Lazy loading is, essentially, throwing all the lightest things as far up the tray as possible, because they’re the easiest items to manoeuvre, and then putting the heaviest items at the rear-most section of the tray, because they’re the hardest to move and that’s the shortest distance you have to send them.
This is basic Newtonian laws of motion stuff that applies to heavy towing too. It takes significantly more effort to move the 10 bags of concrete for that fencing job, than it is to get two big rolls of Agi pipe, up the front of the tray. But does this effort-based loading system have any repercussions? Well, potentially, yeah.
The key design issue with utes, in relation to how it carries payload, is where the rear axle is located relative to the tray. They're not in the middle of the load space, they're right up the front. In fact, they abut the passenger cabin.
The effect this has is it extends the leverage that load applies on the vehicle. This is a torque being applied to the vehicle that, if the axle were located further rearward, would have less effect on the overall behaviour of the vehicle when carrying a payload. The payload is just a euphemism for work.
The work is gravity pulling the pallet of chook poo down onto the vehicle. The rear axle is essentially a fulcrum upon which the leaver is rotating the vehicle through. That's how this works and if you look at all the popular utes, Hilux, Ranger, Triton, BT-50, they’re all doing this.
The wheels are right up against the back of the load space, or at least they’re very close. In fact, they’re much closer to the rear of the passenger compartment than they are toward the rear of the tray.
Where you put the load in the back of a ute really matters. It directly affects the vehicle’s behaviour just like any trailer you hitch up to it will influence the ute. If you hang a big bullbar off the front, that too influences the vehicle. The reason these things affect the vehicle is because of the location of the wheels. They’re not positioned right out on the four corners of the vehicle. They’re positioned to make the passenger cell as dynamically stable as possible.
It is much safer to have as much load as possible in between those four contact patches, which is typically the passengers and this is why it’s classified as a passenger vehicle technically, and not an actual commercial vehicle which has different design parameters. Look at any big Kenworth and how the weight of its load is positioned - in front of the rear wheels.
Look at the location of those wheelsets on both the prime mover and the ‘dog’ trailer
If you need to tow AND carry heavy loads every day, buy a truck >>
If you can imagine in an inertial sense, when you're going around a corner, the various masses inside the vehicle move with the vehicle, constantly. That’s because they have inertia.
That’s the five people, the engine, anything you put in the tray that’s quite heavy like bags of concrete or timber sleepers, - it all has to go in between the back wheels (in the case of the tray) and everything else is in the middle of those four contact points - so that mass is managed. This means it can't act like a pendulum in the way that a tray-borne mass hanging outside of the rear wheels can.
So the way you load your vehicle is going to be pivotal to its stability in a corner.
You can see above how the heaviest load (the orange block) at the rear-most section of the tray is going to have a more profound leverage effect on the vehicle’s behaviour than the lightest load (the blue block). In fact, the blue block is helping to counter the orange block’s effects, but not by much.
The problem here is that as you hit undulations in the road, there is an amplification of the loads transmitted by the orange block. This is caused by inertia. The mass pushed down on the fulcrum and wants to lift the front of the vehicle into the air, effectively. While the wheels may never come off the deck, the symptom you might feel is lightness of the steering at just the wrong moment, such as an off-camber corner with a mild undulation right in the middle.
The sequence of events here starts to play into James Reason’s Swiss cheese model for risk >>. The more risk factors you put into play, the more likely all the holes will line up and disaster strikes.
As you start moving though other directions of movement, such as in yaw (above), you begin to also introduce roll.
That large mass in the tray is not just moving forward; it’s yawing, pitching and rotating, just like the vehicle…
There's this variable in engineering called rotational inertia and there's so much semantic promiscuity about it. Bamboozling terms like ‘mass moments of area’ and things like that, but what it's all really discussing is the same stuff. That is, the different shapes are harder to spin or easier to spin (more resistant or willing to spin as you exert more or less load).
When the ute is yawing, it’s technically spinning. Just not very much. But the fact it’s also got lots of inertia and kinetic energy, means its payload is also full of inertia.
Your ute's not a truck - it's a light duty vehicle - which means it is not as well equipped for resloving the inertial loads placed upon it as it rotates through corners. As it yaws, a truck is much better designed to be harder to spin further when it’s already yawing.
All of these things matter when it comes to stability. Let’s understand why…
ANGULAR MOTION: Why stability matters when carrying loads
At high school in science class the teachers generally try to stay on ‘planet linear’ when you talk about physics, because things that happen in a straight line are just so much easier to understand.
As soon as you start doing spinney stuff and you have to go to ‘angular world’, it becomes really confusing, very quickly. Even the name they tried to keep simple: why do they call it ‘angular’? Well, it's movement through an angle. This includes terms like angular speed, angular acceleration, angular velocity, rotational inertia - all of these things.
If you want to understand how engineers tune a vehicle to account for angular motion, check out Basic Suspension Dynamics: What is a roll moment? >> to learn the basics of vehicle kinematics (there’s another one of those brain-bending terms), or have a listen to the in-depth interview with suspension engineer Greame Gambold here >> to learn how they make modern cars behave.
Okay, so we have Sir Isaac Newton's three laws of motion, whereby arguably the hardest one is number two. It says, formally:
the time rate of change of momentum of a body acted upon by an external force is inversely proportional to the mass of the body and directly proportional to the applied force
Still there? Oh, good. So what the hell does that mean?
What it basically means is, if it is in motion, it’s quite easy to change your ute’s direction of travel with a little nudge >>. But it also means that the heavier the ute, the harder it will be - and therefore the more force required - to nudge it around.
Likewise, if the force is the same, it will resist acceleration (motion) the heavier that object is (the ute). So if your ute is quite heavy, it will resist the force applied to it on the stretch of road at the same speed with the same payload compared with if it’s a smaller, lighter ute with the same forces (velocity) applied to it. The heavier the ute, the more power it needs to move its lardy arse (like a V6 diesel with 180kW in Ranger’s case) compared with the 140kW 2.4 turbo-diesel in a Triton.
This is all well and good for linear motion. But what if we go angular?
Take this example above where two vehicles of different mass are in a controlled environments with the same inputs (the sled, the speeds, the positioning are all controlled). But what’s not controlled by the engineers is their relative mass to each other.
Notice how much higher the Great Wall ute comes off the ground, and begins to rotate much earlier and more profoundly than the much heavier Ranger? The flipside of this situation is that if you put both utes into a situation where they rotated at the same speed, the Ranger would be much harder to stop. Why? A 200kg greater mass.
Every one of Newton's laws (of motion) has an angular equivalent and this basically says that force, mass, acceleration - on angular world - they become torque, angular inertia (rotational inertia) and angular acceleration. So with angular movement it's just the same as linear movement, so far as you've got displacement, velocity and acceleration.
Displacement on planet linear is going from point A to point B. The thing that matter on angular world is shape really matters. Because not all masses spin the same way. Big compact masses spin differently to elongated masses that weigh exactly the same. You've experienced this picking up a bag of concrete versus a timber post both weighing about 20kg.
ROTATIONAL INTERIA: Your heavy mass wants to continue going forward, AND RIGHT…
Every ute (and in fact every single thing in the observable universe) has got a centre of mass located vaguely in the geometric centre of the object. Now, in your ute, the rotational inertia is something you can calculate, but we won’t do that here, because: keep it simple.
Where this matters in your ute is if you increase the weight by, say 20 per cent, but you leave the shape the same, then you double the angular inertia (the rotational inertia). That’s why it’s harder to move a Ranger through an 80km/h corner than it is a BT-50 or Triton - it requires more energy to rotate it.
But if you change the dimensions by the same amount, you make a distinctly different change to the angular inertia of the ute. The rotational inertia of the new Triton will be better because even though the mass has increased, so too has its shape been increased in proportion.
For example, if you made a 2.3 tonne Ranger using the same geometric dimensions of the older, narrower, shorter (in length) L200 Triton, it would be significantly easier to nudge off the road towing, for example, a three-tonne trailer, in the identical circumstances (speed, corner etc) ie if the variables were all controlled.
Now that we’ve done the hard stuff, let’s solve the problem of lazy loading - scroll down for more…
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Put your brain into it
Doing a 15-30 second assessment of your load and deciding which are the heaviest objects and how they should be positioned in the ute is the first key step to avoiding this lazy loading phenomenon.
Now, let’s quickly address the human condition.
Depending on your level of fitness, we all have an energy quotient; a threshold of exhaustion before we need a rest. So, if you’re a bit out of shape, or worse, you should be dedicating your primary energy reserves for the heaviest objects first - because they’re the highest priority to get right. Deal with the biggest, hardest stuff first, then have a break if needs be, and go again on the lighter stuff.
By contrast, if you spend all of your energy reserves on all the light, easy stuff, then you’re going to be tired, unfocussed and ultimately unprepared to lift the big, heavy stuff sufficiently far enough into the tray. So you will succumb to lazy loading by lifting them into a position that is more ‘that’ll do’ and less ‘that’s the spot’.
You need to position the heaviest objects as far forward as possible, right up against the bulkhead between the tray and the cabin. Make sure it’s in the centre as can be reasonably expected.
FAIL: Biggest logs go in first, centralise them, and push each one as far forward as possible
Getting this right really matters. So in addition to prioritising the heaviest and bulkiest up front, you also need to make sure that the moderately heavy things are as close to the centreline of the vehicle.
Moderately heavy objects, if you’re camping, might be the tubs of water, the cast iron camp oven, gas bottles, oversize eski and particularly the tent depending on its size. Many family-size tents can weigh anywhere between 30-50kg, but it’s their length that makes the problematic in terms of loading. So you would prioritise keeping it low, in the centre and against the cabin.
Using this image of the new Triton as a guide, you can see that the further out from the centre your load becomes, the lighter it should be, where possible - obviously. And you can see that the further back, or the higher up, the worse things become for dynamic stability:
And you can see in this example below how the loading has been done somewhat lazily, although with some consideration for the heaviest items, that being the concrete sleepers are low (the keep the centre of gravity as low as possible), and they’re relatively evenly spread.
The steel supports are also centred, but the concrete bags and pebbles are standing out as an example of lazy loading. Admittedly, they’re at least down low in the tray, but they should be up against the cabin bulkhead, not out on the side of the tray.
For items that are all quite uniform in their shape and weight, you want to prioritise getting the majority of the load as far forward as possible. Between the wheelarches first and stacked the highest (green box, below), then aft of the wheelarch mouldings and kept to a minimal height below the walls of the tub (yellow box, below).
At the rearmost point (red box, below), where it’s tempting to put the most stuff as far out into the tub’s cavities as possible, this is in fact the worst possible place to put anything of substantial weight due to the pendulum effect it has on the vehicle. Its rotational inertia.
Ultimately, lazy loading is a condition of the human race. We take the easiest way out, we avoid over exertion and it generally becomes a bad habit we have to work hard to combat.
The best way to avoid a situation like this (below) is to better inform ourselves as to why this happens and implement a few simple, easy changes to not necessarily eliminate the risk - because that’s virtually impossible - but at the very least, better stack the deck in our favour.
Image: Teknikens Värld YouTube
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