Driving Tips for RVs on Corrugated Roads | Safety First
Is there any way to ease the discomfort? Ease, yes. Completely solved? No, but that's one of the challenges of enjoying the beauty and experiences of some of Australia’s most remote areas. Here are some tips for RV owners, particularly dedicated caravanners, looking to seek out adventures on a corrugated road or two (or more)!
What are corrugations, and what causes corrugations on dirt roads?
Corrugations refer to ridges and grooves on roads that your vehicles’ wheels roll up and down over as you drive. They can be likened to the corrugated metal material used for roofing on many homes in Australia. Corrugated steel has a distinct, symmetrical wave pattern like you’d see on a well-used, unsealed road.
Corrugations are usually caused by vehicles. When a wheel goes over a small, natural undulation, it changes the amount of weight on it before it resumes normal distribution. The next wheel follows and does the same thing, each time creating a very small change in the higher and lower sections. Eventually, this forms a pattern of ridges and grooves, which increases with more traffic and becomes a noticeable corrugation.
In terms of what causes corrugated roads, well-known Australian scientist Dr Karl Kruszelnicki cites geophysicist Keith B. Mather’s theory of corrugations. According to Dr Mather, you can never make a road perfectly smooth as there will always be tiny bumps. Wheels bounce in a little hop after hitting one of these tiny bumps. When the wheel comes down and hits the dirt, it sprays dirt both forwards and sideways off the road, leaving behind a little crater, which then becomes the valley of a corrugation. As the wheel comes up out of the valley, it jumps into the air again, and so the valley-and-mountain pattern repeats itself.
The formation of corrugations is a two-stage process - first the corrugations establish a stable pattern, and then spread along the road. Mather saw that the first few corrugations to appear on a "smooth" road were relatively shallow, and very close to each other. But as the corrugations got deeper, they gradually moved away from each other until their height and distance apart had settled into a stable pattern. Once this stable pattern of corrugations was set up, the entire pattern of corrugation would migrate down the road in the direction of travel of the wheel.
But why do all corrugations look similar if cars are all different? That’s because most vehicles travel around the same speed (if you follow the speed limit). So, a bump on the road that makes one car's wheels bounce will also make another car’s wheels bounce. These bouncing wheels will all tend to land at the same point. And that's how the corrugations form. Fascinating, right?
Are corrugations just on dirt roads?
No — they are evident on gravel roads, soft sandy tracks, and other terrains, including bitumen and concrete roads — usually after a break in the road’s surface. They can vary considerably in distance and height, with smaller ones giving your vehicle a minor shake. Bigger ones can easily reach over 20 centimetres in height, making you feel each pretty clearly!
Vehicles today do an amazing job of soaking up the bumps and imperfections of roads, but just because you don’t feel it inside your vehicle doesn’t mean your vehicle won’t. Corrugations make your vehicle work extremely hard and must be addressed to minimise damage. Two valuable elements you can address to minimise damage caused by corrugated roads are your caravan’s tyre pressure and suspension.
Caravan tyre pressure on corrugated roads
Lowering your vehicle’s tyre pressure can help ease some of the discomfort and damage. The degree to which this is done will depend on your vehicle, the caravan you are towing, the road’s conditions, etc., but lowering the pressure to around the 20 to 25 PSI mark is a good start. Having your tyres at a lower pressure helps your vehicle’s suspension cope with the corrugations, and your tyres remain part of the suspension process.
You should also adjust your caravan’s tyre pressure.Typically, the PSI will be similar on your vehicle and your caravan, but a lot depends on the roads, your load, and the speed limit. As a guide, tyre pressure should be dropped by around 40 to 50 per cent. For caravans, the tyre pressure should typically be around 42 PSI, depending on the load in your van and your specific RV, so, again, 20 to 25 PSI is a good start. In all instances, it’s recommended you consult your warranty and service handbook for both vehicles.
Constantly monitoring tyre pressure is vital, and trial and error is a must — don’t be afraid to stop and tweak tyre pressures along the way. Heat is not a tyre's friend, and heat buildup in a tyre is typically caused by compression rather than friction. Stopping regularly can also allow your tyres to cool, allowing you to do a quick safety check. Changing a few PSI can often make a big difference to your vehicle’s ride.
Always check your tyre pressures in the morning before travelling, particularly if you’ve adjusted pressures on hot tyres the day before. Readings, when a tyre is hot, can give you an incorrect pressure reading on your tyre gauge as the properties of the air in your tyres change due to heat. The key is to run pressures that suit the track you are on. And remember to re-inflate back to highway pressure when you hit the blacktop!
Caravan speed on corrugated roads
You also need to work out your ideal speed. Slowing down often helps minimise the effect of corrugated roads on your vehicle and caravan. Most experts recommend a speed of 60–80 km/h. In many vehicles, the sweet spot will be around 60km/h. This is because driving excessively quickly puts a lot of pressure on a vehicle’s shock absorbers. While you may feel like you are floating over the corrugations, don’t be surprised if your shocks fade or worse, particularly on a rough dirt track or road.
Caravan suspension on corrugated roads
A vehicle’s suspension can go through a million daily cycles on corrugated roads. The first thing to consider is whether the tyres on your caravan are up to the load rating. Original Equipment (OE) tyres and rims are specific to your van, but you should check that the tyres fitted have a suitable load rating when you’re travelling on corrugated roads. If not, they may be able to be swapped for a better, tougher tyre and rim set.
As you traverse the corrugated tracks, the pressure in your tyres will increase. That excess pressure exerts force onto the shock absorber, and the shock is now dealing with a tyre that is essentially hard and not absorbing any of the energy coming from the road surface. All the inertia from the corrugation goes through the tyre, into the wheel, into the axle, and straight through to the shock absorber. Caravans being dragged over corrugations have a much harder time than the tow vehicle, and this ‘dragging’ effect actually increases the impact of the corrugations on your van's suspension system. The solution? Adjust your speed as per our guidelines above.
Our last tip is to get your vehicle and your caravan’s wheels aligned. It will save on fuel efficiency, vehicle wear and tear, and overall performance. The preference is to have your caravan loaded in terms of how it’s going to be used for the majority of its life. If it’s going to be heavily laden for constant touring, then ensure it’s fully laden when the alignment takes place. This will allow for maximum tyre life on the caravan and less stress on the tow tug, often avoiding excessive fuel consumption caused by the van fighting the tow vehicle.
How to drive on corrugated roads
There is an old bushman’s myth about driving on corrugated roads — “lower the tyre pressure and high speed are the cure to the vibration of the corrugations”. Not these days! We’ve covered tyre pressure, suspension and speed above, but there are several other factors to consider.
Pick your line
Corrugations are worst when we brake or accelerate, for example, at the crest of hills and at the entry and exit of corners. Outback roads often run through vast open expanses where visibility extends for miles, and on-coming traffic can be seen well in advance. While you are obliged to follow relevant road rules, it is not always necessary to 'stick to the left' if it means you have to drive on the worst sections of the road. Pick the smoothest line and anticipate badly corrugated sections by the changes in the road. By anticipating the changing conditions, you will slow down naturally where required, without braking, and create a smoother ride.
Cattle grids
Some outback cattle grids are pretty rough, and if they are hit at high speed, they can buckle rims or put out your wheel alignment. Try to travel at a speed that will allow you to slow down for them.
Pack it tight
It is difficult to describe how much rattling and moving will occur inside a caravan’s drawers, cupboards, and wardrobes of a caravan! Ensure every glass, can, bottle, plate, and breakable item is wrapped and secured! For expert advice on how to manage your caravan’s tyre pressure and suspension and on a corrugated road, contact your local dealership today.
For expert advice on how to manage your caravan’s tyre pressure and suspension and on a corrugated road, contact your local dealership today.