Unless you’ve had your head buried in the sand for the last 5 years, you would have heard, or seen of dual cab Utes with bent chassis. This has been happening to 4WD’s for years now, and is extremely common in dual cab Utes.
Why do dual cab Utes bend?
If you look at a dual cab side on, and then consider the weight distribution, its pretty easy to see why they bend. Even worse, have a look at some of the setups currently going around Australia today. Massive vans attached to the back of a 4WD with a big canopy on the back, full of gear and the suspension pretty much sitting on the bump stops.
Dual cab Utes are extremely likely to end up with a bent chassis because of the amount of weight located behind the rear differential. Many dual cab Utes only have about 300mm of space in front of the rear axle, with 1500mm sitting behind the axle.
The distance from the tow ball to the rear axle is also substantially longer than that of a wagon.
Dual cab Utes bend for one of 3 reasons. They are overloaded. The load is too far back. A hump, or dip, or wash out is hit causing the vehicle to change forces quickly, and at a high rate.
I’ve seen some dual cab ute camping setups like the above, but much larger that leave you shaking your head. They are a bent chassis in the making every day of the week, and yet they keep getting built, and bought.
What can you do about it?
The fact is, bending the chassis on a dual cab is 100% preventable. Of course, people will have accidents from time to time, and I have seen dual cabs bend even when mildly loaded with good weight distribution.
However, if you do the following, you’ll reduce your chances of a bent chassis to almost nothing.
Distribute the weight correctly
Just because you have a great big tray doesn’t mean you can load it up to the hilt. Manufacturers design dual cab Utes to be loaded evenly. That is, you can’t take the full payload in weight and chuck it in the tray.
You should have a decent portion of weight forward of the rear axle. This includes passengers, fuel, water, and anything heavy.
If it must be in the tray, put all heavy items over the top, or forward of the rear axle. We have a 45kg battery which sits about 150mm in front of the rear axle, and anything heavy is jammed as far forward as I can get it.
Ensure you are under GVM and axle loads
By law, exceeding your maximum vehicles weight (GVM) or axle loads, you are driving an illegal vehicle. This also means your insurance company doesn’t have to pay out any claims. If you have a dual cab ute that is fairly heavy, take it over a weigh bridge. I guarantee you’ll get a shock.
Not only do you need to be under the maximum GVM, but you need to be under what the manufacturer sets for axle weights. This means you can’t have too much weight on the front wheels, or too much on the rear wheels (or both!). If you are towing, make sure you check the weights with the trailer hooked up.
Some people take way too much gear, or put no thought into weight reduction. Steel canopies, steel trays, underbody toolboxes, under tray drawers, 4WD water tanks, big batteries, extra jerry cans and what ever else you might have is not going to help your situation. Do everything you can to reduce the weight in your dual cab’s tray!
If you are towing a trailer, you will need to be substantially under the GVM to be legal, as the townball weight of your trailer comes out of your payload, and the leverage adds a lot of weight to your rear axle weight.
Don’t tow anything with a ridiculous tow ball weight
This is probably going to upset a few people, but a dual cab Ute is not the best or safest option when it comes to towing. This relates to the distance between the rear wheels and the tow hitch. A wagon will tow a big trailer substantially safer and more comfortably than a dual cab will.
That’s not to say you can’t tow with a dual cab Ute, but the sales pitch given by vehicle manufacturers that sell dual cab Utes is a total farce, and completely unsafe. Not only can the 3500kg tow rating only be done under extreme circumstances, towing a trailer that heavy with such a light vehicle is a recipe for disaster.
I would suggest that for most dual cab Utes, towing anything with a tow ball weight of more than 200kg is asking for trouble. This is especially the case with a loaded Ute. Again though, the way to tell if its OK is to weigh the rear axle weight when loaded up, and hooked to your trailer. If its over, you aren’t legal. Please know that the tow hitch types vary in their leverage applied, particularly if they are different lengths!
Drive more cautiously
There’s no doubt that 4WD tracks put more stress on your vehicle. Wash outs, pot holes, dips and ruts will all increase the chances of a bent chassis, especially if you hit them hard. The more cautiously you drive, the better off you will be in terms of looking after your 4WD and reducing repairs needed, and your chances of breaking a chassis are greatly reduced.
Buy a more suitable vehicle
Again, this will probably upset a few people. Sorry, but it is what it is; I’d rather be blunt than sugar coat it.
If you have a dual cab Ute with a heap of gear in it, and towing a trailer that is heavy with a big tow ball weight (250 – 350kg), you have the wrong vehicle for the job. You’ll see this when you go over a weighbridge, as you will be over GVM, GCM or axle ratings.
You can look into the world of GVM and GCM upgrades, which will give you some leeway, but at the end of the day you are asking far more from the vehicle than it was ever intended to do. Better you know about it and make an educated decision, like moving to a light truck than get involved in an accident and find out then, when its too late.
Do air bags make chassis bend?
Air bags are one of the more controversial topics you’ll discuss in the world of heavy 4WD’s. They are a fantastic option, when used sensibly and within the design parameters of your 4WD.
If you want a blanket statement, air bags will not increase the chances of your chassis bending as long as you are under the GVM, GCM and axle ratings.
Now, lets look a bit closer at the different spring types. If you have a vehicle with independent rear suspension, or coil spring suspension, then air bags apply their load in the same position as the coil does (just inside of the coil instead of the outside). Providing you stay under weight, you won’t have any issues.
Leaf springs on the other hand, make use of air bags in the centre of the spring itself, creating a third point where the chassis takes load. Some people will tell you this makes the chassis bend, but if you look at where the chassis bend, its no where near where the air bags sit.
Air bags on leaf springs are a fairly popular option, as its impossible to get a set of leaf springs that will ride comfortably when the vehicle is unloaded, but be able to take a fair chunk of weight when loaded.
For vehicles that see varying amounts of weight, air bags are a great option, but, don’t use them as an excuse to add more weight; use them to level your vehicle and stay within the manufacturers maximum weight in terms of GVM and axle ratings.