Corrugations in your 4WD; what to do about them

A substantial amount of Australia is connected by gravel roads. If you’ve done much gravel driving you would have heard of corrugations. They can be absolutely terrible both from a comfort and potential damage perspective.

What are corrugations?

Corrugations refer to the lumps that develop on tracks over time. They are called corrugations because they form a similar shape to corrugated iron, like what you’d see on tin roofs.

They can vary from just a few cm tall to over 150mm and the distance between 150 and 300mm.

Basically, they shake the life out of anything going over them!

Corrugations and pressures
Corrugations on the way to the Bungle Bungles

Where are corrugations found?

Just about every gravel track will have corrugations on it within Australia. When they are graded they are smooth, but it doesn’t take long to develop corrugations.

You can also find corrugations on sandy tracks and along the beach.

Most often, corrugations are worst exiting a corner, or going up a slight incline. People have a habit of accelerating too quickly out of both situations, and the wheel spin and incorrect tyre pressures contribute to making nasty corrugations.

Israelite Bay corrugations
You’ll find corrugations on sandy tracks as well as gravel tracks

How to drive on corrugated roads

Corrugations are a part of the Australian 4WD network, and there are a number of things you can do to make the ride more comfortable, reduce the stress on your vehicle and limit the damage done to the roads.

In essence though, its all about balancing a number of factors together.

If you don’t take the time to do this, you’ll have a terrible ride and something is likely to break on your vehicle. Check out the ultimate guide to gravel driving for more information, but this will get you started:

Tyre pressures

The most important factor on corrugations is Tyre Pressures. Your suspension works extremely hard on corrugations, with shock absorbers easily hitting 100 degrees Celsius from the continual dampening on bad roads.

In order to reduce the stress put on your suspension (and the rest of the vehicle), you should be deflating air out of your 4WD’s tyres when you hit corrugations.

By letting air out, you allow the tyres to mould better to the shape of the corrugations, and they absorb some of the shock. However, be aware that on corrugated roads, the continual flexing of your tyres side wall creates a considerable amount of heat, and your tyre pressures will rise because of this.

On the Gibb River Road, we saw our 80 Series Land Cruiser tyre pressures on the rear easily go up 6 PSI from cold to hot.

How much air you take out depends on how bad the corrugations are, what speed you are travelling and how much your vehicle weighs.

The general rule to tyre pressure for corrugated roads is to remove about 30% of air from your cold pressures driving on road.

For example, if you normally drove at 45 PSI, you’d remove 30% of the air, taking it to around 30 PSI.

Airing down 4x4
Taking air out of our Land Cruiser tyres at the start of the Gibb River Road


Corrugations and speed is a bit of an interesting one to balance. The faster you go, the smoother the road feels as you just skip the tops of the corrugations. However, this also you contact the humps less and less, and your ability to safely turn and brake is dramatically reduced.

Balancing your speed and tyre pressure is imperative; you want to be going quick enough to avoid the harsh bouncing, but not so fast that you aren’t driving safely for the conditions.

There’s no set rule either, as corrugations vary so much. Sometimes you can get away with tyres at around 24 PSI cold, and sitting at about 70km/h in relatively bad corrugations, but it vastly depends on what is safe in any given situation. Don’t put your lives at risk; take it easy and arrive alive.

On the other hand, crawling over corrugations is also insanely painstaking and not great for your 4WD either.

Gravel road speeds
Pick a safe, comfortable speed to drive at

Engage 4WD

If you are driving on corrugated roads, you should have 4WD engaged. If your vehicle is all wheel drive anyway then that’s a great option. You are better to engage the centre diff lock if possible, and drive with all 4 wheels. This gives you much better grip for cornering.

4WD Dial
You want to be in 4WD high range on the dirt for lots of different reasons

Stay out of the dust

If you are following another vehicle, you should be back far enough that the dust isn’t covering your vehicle. This ensures you can see clearly in front, and can react should conditions change. It also ensures your engine doesn’t suck a gut full of dust into the air filter.

Reconn R2 in the dust
If you’re in the dust of a vehicle in front, you are way too close

Damage corrugations can do

When you think of 4WDing, perhaps gravel roads are not where you would expect a lot of carnage to happen. The truth is, corrugated gravel roads put a heap of pressure on everything on and in your vehicle, and do a lot of damage relative to your average 4WD days.

The endless shaking and bouncing around stresses everything from shock absorbers and bolts to tyres, wheel bearings and anything that can fatigue over time.

It’s great practice to have a look in your engine bay and under your vehicle after a days driving on rough roads, to look for fresh markings of something that’s come undone, or is working its way loose. Wobble things back and forth as you do your inspection to ensure everything is tight as it should be.

Cruisemaster Alignment
Check everything after doing corrugations as it can easily loosen nuts and bolts

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