Rattle and roll!

Rattle and roll!

So we also aim to look at some defensive driving, an area where many accidents occur is on gravel roads. Speed and the resultant “loss of control”are a lethal combination. As are the sandy verges on the sides of gravel roads. We recently travelled to Kenhardt from Sutherland on a long beautiful gravel, admit was not treacherous but care needed to be exercised as there were some corrugations and a good deal of thick sand. We did notice a brand new car that had rolled en route and could only surmise that it was a problem with speed, especially seeing that the car had rolled on a bend.

So let’s look at the washboard effect of corrugations, they are generally more prominent on gravel roads where traffic is busier. The softer surface is the main cause of the problem.

Vehicles riding over undulating surfaces will detect a degree of softness and may have to brake to slow down. This reduces weight on the wheels which then compress later. Here we begin to create a tiny crest and dip. The next wheel follows and the problem is exacerbated. Subsequent traffic worsens the problem and corrugations form given time and traffic.

The tiny crests and dip go through each other until you have a corrugated section of the road.

Grading the road is a short-term fix as it softens the top surface and makes it easier for corrugations to form again.

Tar would be a solution but budgets do not allow that as many of these roads are small arterial routes! So you won’t see corrugations on tar roads but you may find undulating surfaces especially where there is intensive truck traffic. Here you will also have to be careful as it does cause a degree of “bounce” at high speeds.

So you will be unlikely to find corrugations on your typical 4×4 trail as they are low-speed routes.

Wheelspin on sandy routes may cause ruts but won’t form corrugations, the same applies for muddy sections. Very hard routes will also stay the same even if you brake hard.

However, be careful on uphill corners where drivers brake hard and then accelerate as ruts may be formed.

In the long run, it’s a combination of the softer gravel road, your speed and the number of vehicles that traverse the terrain.

  • Corrugations are unavoidable given that these roads support trucks, tractors and numerous other vehicles.
  • Strangely because they “bounce” lighter vehicles cause more corrugations.

So you will get more wheel spin on a two-wheel drive vehicle and need to compensate, four-wheel drive vehicles are more accommodating.

Speed is important as if you are driving too fast loss of control is a consequence.

Braking is also a problem as it could lead to loss of control especially if your speed is a bit high.

Be comfortable and gauge your speed, corrugations can be scary but if you are at a comfortable speed all should be well. For long stretches of gravel, it is worth dropping tyre pressures to add comfort to the ride ( maybe 10 % of OEM recommended pressure ).

It is worth relaxing and enjoying the trip – remember you still have a destination and end destination. And secure loose items they may jump around. Enjoy the ride!

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