corrigation on dirt roads

this is something i have always wondered as well, cos they are always the same size and space apart. hope you get an answer ill be watching this thread

Dr Karls Eplanation

He is working on it??

You may be interested to know that corrugations also occur on steel rails on a railway. They can either be short wave (about 2 - 40mm peak to peak) or long wave (several centimetres peak to peak)

The short wave type can be heard when travelling in the train as a roar. Railways actually spend a lot of effort grinding them out.

I believe they are related to suspension bounce. A small initial displacement will cause a small bump which gets deepened by each wheel passing and as the suspension bumps up and down the corrugations grow. Often an irregularity in the rail surface such as a weld will initiate the corrugations.

I believe that road corrugations form the same way. A small defect and then oscillations in vehicle suspension start them propagating.

Bruce

Bruce

I have often wondered what the effect of vehicles dragging a short length of heavy(ish) chain behind each wheel track would stop the ridges forming, or gradually smooth those already there.
(Some what along the lines of long dresses polishing the floor on the Royal Albert Hall.)

The Rangers in the Bungles "grade " the road by dragging half a dozen truck tyres behind their ute. Helps a bit by knocking off the top of the ridge but you'd have to do it 6 or 8 times to be effective. Cheers, Warrie

I heard lower tyre pressure can help aviod the corrugations happening on bush tracks,maybe it applies to dirt roads also?
The tyre with lower pressure doesnt spin so much

There really isn't any easy explanation on how corrugations form. Check outDr Karl's webpage for a good read

Yes,, corros can start on any dirt road..
There only has to be a dip in the road and then they start..
The tale of a certain speed to rise on top of the corros is crap,,,,,if i am in a hire car (britz etc,,,),, then maybe 80 is ok,,,,, but in my own car i dont care if i slow to 10kmh...
There isnt a corro on the planet that is a hassle to me,,, because at the right speed you cant even feel them....
Forget about tyre pressures and shockers etc,,, correct speed is the only answer...
We normally see corros when we are outback on holidays right??
Whats the rush?...
Normally there is one hero in the group that trys to keep everyones pace up..
15kmh an hour??? on a good days travel we have gone 100kms,,, thats far enough some days..
And that hero is normally asking us for spare nuts and bolts and cable ties at each nights camp... LOL...

As long as you take traffic conditions and visibility into consideration - travelling on the RHS of the road is normally always smoother. Sort of supports the wheel bounce theory as the corrugation angles are generally steeper on the side facing you.

I have found 80kph to be good on some corrugations. Other spots I have been down to 15kph - its all about driving according to the conditions and your experience.

Thanks fellas, Looks like it is a trial and error job on what speed to travel at.
Its funny that it is all across the road and not just the wheel tracks.

Just down the road outside the concrete plant and semi parking lot there are corrigations that have finally made themselves into the tar....wonder if trucks (and lg cars etc) can cause corrigations by gear changes and braking etc.....they also seem to be quite prevalent just before and after cattle grids too....!mmmmm????

Great question Damien. My own personal theory is that it has much more to do with traction than anything else.

A mate of mine who was a country shire engineer once pointed out to me that the worst corrugations in his shire where near road junctions where there was lots of acceleration and deceleration. This was especially pronounced near farm gates (ie where they accelerated or decelerated onto the shire road) and about 15 or 20 yrs ago when constant 4WDs like 80 series, Discos & Rangies became more prevalent as the vehicle of choice for the farmers using his roads you could pick who had them because the corrugations near their farm gate were great diminished to the point of being virtually non-existent.

Also, if you are in a long convoy of 4WD's all driving with 4WD engaged, the corrugations are more diminished at the end of the convoy than the start.

That's my experience and I often think Track Care or 4WD clubs & websites etc ought to actively encourage people to engage 4WD at the slightest provocation, ie when they are in anything other than very firm conditions that would damage their drivetrains if they drove in 4WD.

That's my two penneth worth!

Paul B Kalgoorlie WA