Driving corrugated dirt roads

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Perth, Western Australia
Hi Guys

I have just come back from a trip up to kalbarri and shark bay in WA. First of all for those of you that have never been up that way i totally recommend it the place is amazing.
One of the trips I did was out to the gorges in the Kalbarri National Park to get there was 26kms of corrigated dirt road. To be completely honest I really couldnt remember about driving on these types of roads whether you drive fast or slow or any other technique to it. I wouldnt mind hearing what others do to tackle these types of roads?
Cheers.
 
It depends on the road, we have a lot of corrugated roads around here and some you can reach a certain speed and you skim over most of the holes, others it really doesn't matter what speed you are at it's just rough as guts. Each road needs to be judged on it's own merits there is really no one size fits all driving technique because no two corrugated roads are alike.

In many cases we are lucky because our corrugated roads are not heavily trafficked so we can pick the side of the road that suits us bit there always one hole, or one section you don't expect.
 
Pfffft 26ks. Go and do the Canning Stock Route, 1800ks of them, by the end you'll be an expert.

As Krafty said you drive to suit the conditions. The WA desert tracks tend to have saw tooth shaped bumps so driving one direction is bad the other way is down right unbearable.
 
After 14 days of this you wish to never see another dirt road in your life.

DSC_0553.jpg


Top speed of 15kph for 4 straight hours on this particular stretch near Kunawarritji
 
Drove the Birdsville and oodnadatta tracks middle of last year, plenty of corrugated roads on that trek. We found the magic sseed(s) to be either below 60km/hr, or above 80km/hr - needless to say we hooked along at a pleasant 90-100km/hr.

We also found that, conditions permitting (having EXCELLENT visibility), driving on the opposite side of the road greatly reduced the severity of the corrugations.
 
The thing to watch on corrugated roads is your shocks. Thin-shaft shocks that have poor heat dissipation rates will fail as the valves pass their heat tolerance and fail, or the things warp (which is a disaster out there).

At high speeds your cabin might feel like it's all going smooth but your wheels, springs and shocks are working at a frantic pace and unless they're designed for that sort of treatment (standard shocks are not) you will risk the destruction of the shocks. This also applies to the trailer you may be hauling.

In Australia's outback there are some HORRID roads. We went on the Ernest Giles Rd - it's 99km of dusty corrugations with some extremely soft sandy spots (you need to hit those at about 60km/h in 4HI to sail through them) but the corrugations really let their presence be known. At a comfortable pace (10-15km/h) and riding the verges where the corrugations were less pronounced, it takes a lot of time - and you use a LOT of fuel - on those roads.

I also suggest refraining from exiting the vehicles too much. What you can't see in this photo is the number of smooth 'S'-shaped undulations that crossed the road.

3741.jpg
 
Old T, I understand what you're saying about the shocks. But what about the torsion bars?
And why would you use so much fuel?
 
IFS in the D40, no torsion bars - but torsion bars and springs ought to be fine, it's just metal bending and because they're designed to bend, you don't have to worry too much about them (relatively speaking, compared to shocks). Better springs are a good idea, especially if you're going to load the vehicle up.

Fuel is easy. If you're doing 2,000rpm in second gear you're doing around what, about 25-30km/h? In top gear (D40) you're doing 100km/h for those RPM. Watching the rail pressure in mine (and the fuel flow rate), there's very little difference in flow/consumption rates despite the difference in speed, which means that over one hour, you'll get 100km behind you for your 10 litres of fuel, and I'll only get 30km. That means that I'll use 3 times the fuel to cover the same distance.
 
Oh, I understand what you're saying. However... There is that certain equilibrium point, or sweet spot, where fuel economy is great with big k's. For eg, I can sit on 70 for a whole tank and get 750k's out of it, but if I were to sit on 100k I couldn't get much more than 600k out of the tank. There's a certain speed you can sit on where you gain in k's and economy. Remember the engine has to strain less to maintain that speed, so you use less too. But obviously with extra work the engine has to do from the corrugation then that could make up for all that easy work.

I thought torsion bars would have a bit of strain on them still? And if the back end has no weight I couldn't see the shocks loosing out all too soon either.
 
Oh there's a sweet spot alright, and in a turbo diesel engine it is right at the point where the turbo starts to come up to full song. In the D40 it's in the 1800-2000rpm region. In the D22 it's a little higher. It's basically the point where (look at a dyno chart) your power rises up fast - just before it starts to level off.

Up to THAT point, you're putting in a little more fuel and getting a lot of power for it. Beyond that point, any more fuel that you put in is only giving you a marginal increase.

For a D40 on the road it equates to around 95km/h.

The whole suspension system still has strain on it on heavily corrugated roads, absolutely, but spring steel can handle it a lot better than a steel rod with valves moving through an oil bath. The oil, valves, rod and casing all heat up rapidly, sometimes to the point of seizing, bending or even breaking.

A seized shock will solidify the axle until it breaks - every bump will feel like a colonoscopy performed with a mallet. If the shock breaks, the car will wallow around on that wheel, as the spring has free rein to keep on bouncing.

As for an empty tub - the weight is all relative. The vehicle weight still sits on those wheels whether the vehicle is stopped or in motion. I went looking for some video of a ute on corrugated roads but I couldn't find anything. Maybe someone else will have some luck - or we will just have to get our video camera out! I have some footage of my Navara on the Ernest Giles Rd, but it was loaded and towing the caravan and being driven sedately so it isn't a good example to answer your specific question about unloaded weight.

Whether there's a load or not, the back end still works - just go to the local supermarket and watch an unloaded ute on a speed hump, I guess.
 
hi old tony what does your van weigh the ass of the nav seems to be down a bit or do you just have the canopy full of amber fluid if thats the case you need to spend more time in each stop over its no use carying all that beer if ya not going to drink it
 
Haha! It's actually saggy springs. Ironman LoadPlus Helper Springs don't last very long, my suspension has had it. Sax Suspension triple-action leafs are going to be the next upgrade, and I'm heavily leaning towards Bilstein shocks because they're rebuildable.

At that time, we had the 180kg of ball weight mounted on the weight distribution hitch, and the tub full of gear - fridge (full and working), 4 jerry cans with exactly 20L of diesel in each one, tools, generator, petrol and power cables etc. It certainly didn't help on the corrugated road!
 
Haha! It's actually saggy springs. Ironman LoadPlus Helper Springs don't last very long, my suspension has had it. Sax Suspension triple-action leafs are going to be the next upgrade, and I'm heavily leaning towards Bilstein shocks because they're rebuildable.

At that time, we had the 180kg of ball weight mounted on the weight distribution hitch, and the tub full of gear - fridge (full and working), 4 jerry cans with exactly 20L of diesel in each one, tools, generator, petrol and power cables etc. It certainly didn't help on the corrugated road!

still tony thats a fair load ! For a d40 that is, but seriously you kouldnt have fit much more in . I was thinking about a set of those iron man load assist springs or still tossing up on air bags but mine currently has standard springs with extra standard leaf added thanks to sparra has realy stiffened the back up and also lifted by thickness of leaf doesnt flex at all with my camper on so all good
 
For what it is worth!

I have driven the vast majority of these tracks over the years, I have found that good tyre choice and correct suspension set-up with tyre pressures around between 26 and 28psi and travelling at speed between 60 and 80ks works for me. This suits dry conditions.

Regards,

RLI
:rambo:
 
Dont under estimate tire pessure. Mine seems to work nice round 20 to 25psi mark. Anything north of 30 and your wastin your time.

Larger profile tires seem to help as well. Have had a few comments on how well mine rides with 33's instead of 31's.
 
Knowledge from living on the Great Central road

Hey Guy's,

Alot of great advice. I have lived in the Desert for around 5 years now the last two and a half years on the great central road. (240km west of Uluru).

As mentioned previously shocks are critical. I get to drive a lot of cars with alot of shocks. The best i have found so far is Koni.

The one thing you can adjust to make your ride more comfortable and look after your car is your speed. I always thought the faster you went the smoother it was until i actually measured the vibrations inside the car. turns out the extra speed does very little for the ride.

Tyre pressure is the next variable you can control. When i measured the effect of tyre pressure on vibration in the car i found the lower the pressure the better the ride. (please know you cant run 18psi at 90km).

If your interested to know more and see the graphs from my experiments head over to Your Trip Right.

http://www.yourtripright.com/driving-corrugated-roads.html

I hope this helps some people, any questions about this or questions about a trip your planing to the area feel free drop me a line.

Brett
 
Dropping some air out of the tires helps. Ive done most of Len Beadells outback track and know that sitting over 80km/hr if possible is the best speed as you float over them. My rig is far from stock but the remote res's on the fox coilovers handled the corrugations of the connie sue highway much better than when I did the Gunbarrell with the tuff doug foam cells.

While it may as well be out of most peoples budgets to modify their nav to the extent I have. I believe having the correctly rated leaf springs tot he load you are carrying and a set of decent remote res shocks is the key
 

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