One of the many important driving techniques that we teach on our courses is how to avoid rolling a 4WD.  Ladder rail chassis 4Wd’s are limited in their handling capabilities due to their high centre of gravity.  They are very easy to roll over.  A very short explanation of the skills involved in reducing the chance of a rollover is – Swerve Once, Don’t Swerve Twice – and – BRAKE BRAKE BRAKE

In this now famous Youtube clip we can see the old and new model Toyota Hilux driving through the Moose (or Elk) Test at about 60kph.  While there are many opinions about the handling abilities of the Hilux, everyone should understand that this is normal behaviour from a ladder rail chassis 4WD vehicle.  The high centre of gravity caused by the chassis sitting high over the suspension makes for very unstable handling.  Driving through the Moose Test the weight of the car is sent to the right, increasing inertia to the right, as the driver swerves left (driving on the right side of the road in Europe).  The driver then swerves right – maybe to stay on the road or avoid an oncoming vehicle – and the weight of the vehicle is transferred to the left and accelerates past vertical with a lot of inertia.  The result is that on the second swerve there is more lateral force and therefore an increased chance of the vehicle rolling over.

While some criticism can be leveled at Toyota for the poor handling of the Hilux, other manufacturers are not off the hook.  Have a look at the Nissan Navara and Mitsubishi Tritons front right wheel.  They both demonstrate the handling issues of high centre of gravity vehicles.  The Ford Ranger develops a slide on the third swerve and is saved from a potential rollover by the reduction in speed.

This all occurs at 60kph.  How would these vehicles handle at 80kph or more?



This post was prompted by an email that I receive a few days ago from a past student.  The email really does capture how easily a simple drive on country roads can turn into a potential tragedy.  I have spent many years as a police officer investigating crashes, including 4WD rollovers.  The scenarios are usually the same as what is described below.  This one had a happy ending.

“Hi Greg.  I thought you might like feedback, especially with regard to your previous line of work.  Even though we all like to think we can drive and know it all ~ and maybe it didn’t make that big of a difference in the end result (because I’m one of those great drivers ha ha) but I think your training played a certain role in this incident.

Bringing the family home from a holiday away in Streaky Bay the other week in a fully packed Pajero (misses ~ 3 x kids ~ luggage ~ she was a pretty heavy vehicle) we came across quite a lot of dead roos on the side of the road.  While the misses and I were talking I gave her the speech about only swerving once never twice and the mechanics of why that it is important.  We like to think we already know that, and the handling capabilities of our vehicles as well as our own skill levels in handling a vehicle.  Anyway it was interesting that after your course and me giving the speech to the misses it was only an hour later I was put to the ultimate test.  Traveling at 110km about an hour this side of Port Augusta some peanut pulled out of a side road, into the intersection and stopped dead in front of me in my lane!

The brain under pressure is an amazing thing.  I assessed my 3 different options, none which were that great.  I could have swerved right into oncoming traffic and hope he doesn’t go further forward, just T boned him, or head left and try and squeeze between his boot, a pole and the car behind him.  The last is the option I took and we made it safely around.  Now long story long, I think in the middle of that the thought crossed my mind that if I head left I’m all out of options as we can’t swerve twice, but we made it.  I do remember braking and not swerving twice being a part of my 200 different calculations whilst the anchors were fully deployed and the misses was screaming.

I just thought it would be worth it for you to know that not always the speeches are landing on deaf ears.  It probably bores the hell out of you giving the same speech each lesson but I reckon in this case that speech helped in reminding me and freshening up on skills and in the end probably helped towards saving a fair bit of carnage.  You can never be to good or too old to take a refresher or learn new things. However if anyone asks, it was my mad skills as a driver.  ha ha hah!”.

This chap had previously done several mine spec driving courses so he was actually very competent in a 4 wheel drive.  Reinforcing 4WD skills is just as important as learning them.

If we think the answer is a monocoque chassis 4WD vehicle then the answer is yes… and no.  There is still enough weight in a monocoque chassis vehicle to cause it to roll over.  This is partly due to manufacturers building monocoque 4WD vehicles with heavy ladder type sub-frames.  The idea being to keep weight down, and improve handling and comfort over rough roads.  The Jeep Grand Cherokee is a good example of these hybrid chassis vehicles.  In my opinion there is nothing wrong with the Jeep Grand Cherokee.  It is very good in difficult off road conditions and behaves like any other high centre of gravity 4WD vehicle.

So the message is hopefully clear when driving ALL vehicles.  SLOW DOWN…AVOID SWERVING DRAMATICALLY…SWERVE ONCE…BRAKE BRAKE BRAKE.  Stay safe out there.