Rollovers - what causes them?

Submitted: Friday, Jan 13, 2006 at 15:18
ThreadID: 29661 Views:1990 Replies:12 FollowUps:16
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4WDs always get a bad rap as being prone to rollover due to their higher centre of gravity, but under what circumstances do 4WDs actually roll while driving on a relatively flat road? Often see pictures of vehicles which have rolled on a straight stretch – what causes this? Driver fatigue, tyre failure, swerving to avoid livestock, or something else?
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Reply By: Member - Davoe (Widgiemooltha) - Friday, Jan 13, 2006 at 15:50

Friday, Jan 13, 2006 at 15:50
I have been in a 2wd that rolled. it was a result of a front tyre blowing out. I was in the back of the panelvan and it looked like someone had just reefed the wheel to the left. Vehicle slid sideways and flat tyre dug into the bank sending us over and over and over - longest 3 seconds of my life bouncing around with tool boxes, spare tyres, esky, guns etc etc like on spin cycle
AnswerID: 148333

Follow Up By: howie - Friday, Jan 13, 2006 at 20:21

Friday, Jan 13, 2006 at 20:21
yep, blow-out on the front tyre did mine,with the same result. ( GU + camper)
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Follow Up By: rickwagupatrol - Friday, Jan 13, 2006 at 23:50

Friday, Jan 13, 2006 at 23:50
When it comes to a blown front wheel, the problem usually occurs the second the driver hits the foot brake. doing this causes the blown wheel to hit the bitumen quicker and harder, thus usually flipping the vehicle. And this applies to any vehicle on the road, no matter how big or small it is.

The best way to survive a front tyre blow-out is to leave it in gear, put both feet on the floor, get a real good grip on the steering wheel and either let it shed the speed by itself, or get the front passenger to use the handbrake,,,,,one click at a time.
For those with a camper and one of those brake controllers that allow you to use just the camper brakes, hit that instead of the handbrake and let the camper pull you up.
I have survived more blown steer tyres in trucks than i care to remember and always remember the words of my instructor.....NEVER touch the foot brake if a front tyre blows.

rick.
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Follow Up By: howie - Saturday, Jan 14, 2006 at 00:41

Saturday, Jan 14, 2006 at 00:41
sorry rik , but when you have only got 3 tyres left and the front left rim is digging into a dirt road, you have not got much choice in the direction of the vehicle.
i never touch the brakes in a "skid" situation , but theory is good, most people do not posses the skills to avert off and on road skids. i honed my skills driving on snow and ice ,but you can't stop the direction of a vehicle in some conditions.
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Follow Up By: Member - Davoe (Widgiemooltha) - Saturday, Jan 14, 2006 at 08:51

Saturday, Jan 14, 2006 at 08:51
Yep sorry riik but sitting in the back i had a real good look at what happened - one minute we are going along - next the steering wheel was just wrenched hard left - Maybe if you were expecting it you could hang on but we were sideways off the bitumen before any human could get anywhere near the brake
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Reply By: geocacher (djcache) - Friday, Jan 13, 2006 at 15:56

Friday, Jan 13, 2006 at 15:56
In my experience they result from the attempt at recovery from an unplanned deviation.

Through fatigue, looking down to change a CD or similar, spilt drink, phone use, dodge something on road etc. the driver swerves to recover. If they've ended up in the oncoming lane the accident is usually a head on or a glancing blow if there is one at all. Often it only results in a near miss.

The most common cause of the rollover is where the driver ends up in the gravel on the verge and is partially sideways as a result of a violent attempt to correct their path. As soon as they get grip or shortly afterwards the vehicle tips over. Often they manage to hold it until they get to the gravel on the opposite side but a subsequent correction there ends up in the same problem.

It's not a problem isolated to fourwheel drives. The same happens to people movers and vans, and even often to family sedans & wagons.

I've been to lots of em.

Dave
AnswerID: 148334

Follow Up By: Scubaroo - Friday, Jan 13, 2006 at 16:01

Friday, Jan 13, 2006 at 16:01
Yeah, did the old "720" thanks to both left wheels in the gravel while on my P plates many years ago in a Datsun Stanza doing about 80kmh. Still can't convince my old man that I wasn't swerving to try and hit the poor old rabbit I apparently cleaned up in the process (he found it when he drove down to inspect the site). Luckily that only resulted in buggered wheel bearings (and a small brown stain), and I ended up down the embankment on the side of the road WITHOUT gum trees, so no panel damage!

Makes sense that a similar situation would roll a taller (or faster) vehicle.
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Follow Up By: porl - Friday, Jan 13, 2006 at 16:13

Friday, Jan 13, 2006 at 16:13
and, tragically, happens a lot i've notice to tractors too.
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Reply By: Member - Phil G (SA) - Friday, Jan 13, 2006 at 16:20

Friday, Jan 13, 2006 at 16:20
Easily done on greasy muddy roads.

I know of one instance with a well set up standard vehicle with 4wd engaged, travelling at a cautious 40kph on a wet greasy outback track, hit the edge of a wombat hole, and the vehicle slid sideways, lost traction, and a rear tyre popped off a rim and it slowly went over on its side.

Another instance where a driver sliding on Sliver City Highway in the wet did something similar.

Cheers
Phil
AnswerID: 148337

Reply By: Member - Alan H (QLD) - Friday, Jan 13, 2006 at 16:28

Friday, Jan 13, 2006 at 16:28
Had a mate roll over while stationary.

He pulled up on the side of the road to help another driver with a flat. The edge was wet and gave way under the vehicle and it slowly fell over while the vehicle was staionary. No one was in it as they were out fixing the other vehicle's flat.

He is very cautious where he pulls up now. (It happened up Darwin way in the wet)
AnswerID: 148339

Reply By: Shaker - Friday, Jan 13, 2006 at 16:49

Friday, Jan 13, 2006 at 16:49
How about due to excessive lifts & "temporarily" disconnected sway bars??
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Follow Up By: cokeaddict - Friday, Jan 13, 2006 at 17:10

Friday, Jan 13, 2006 at 17:10
dont be silly shaker...no one does that mate
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Follow Up By: gramps - Friday, Jan 13, 2006 at 17:43

Friday, Jan 13, 2006 at 17:43
ooohh don't start that one again Shaker :)))))
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Follow Up By: Shaker - Saturday, Jan 14, 2006 at 14:22

Saturday, Jan 14, 2006 at 14:22
Unfortunately, sometimes the truth hurts!
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Reply By: Beemer - Friday, Jan 13, 2006 at 19:56

Friday, Jan 13, 2006 at 19:56
G'day Guys,

Word should be Crash instead of Accident, most tend to happen on straight roads due to a combination of things such as lack of concentration. This might lead to sudden over correction or too much speed. So many other factors, poor inflation, poor suspenstion. The list goes on, How many out their have driven along and suddenly found themselves crossing the centre line and then correct themselves. Lots of factors but most is probably a combination.
On another note, how many of you have cargo barriers or secure your stuff in the vehicle. I have attended hundreds of accidents and it is of concern how many thing inside your car can contribute to injuires even at low speed.

Jake
AnswerID: 148397

Follow Up By: Footloose - Friday, Jan 13, 2006 at 22:16

Friday, Jan 13, 2006 at 22:16
I've never suffered a serious accident or rollover touch wood (grabs his head :). However I wouldn't own a 4wd without a cargo barrier. No way. They take up space and are inconvenient, but can save your life.
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Follow Up By: Member - Brian (Gold Coast) - Saturday, Jan 14, 2006 at 08:43

Saturday, Jan 14, 2006 at 08:43
"They take up space and are inconvenient, but can save your life. "

YES!!!!!!
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Reply By: Kiwi Kia - Friday, Jan 13, 2006 at 20:19

Friday, Jan 13, 2006 at 20:19
Several reasons or a combination.

High centre of gravity combined with a sudden swerve

High centre of gravity combined with a swerve + low tyre pressure

Etc. etc. etc.
AnswerID: 148411

Reply By: glenno(qld) - Friday, Jan 13, 2006 at 22:03

Friday, Jan 13, 2006 at 22:03
Troopy + backpackers
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Reply By: Member - Paul P (Bris) - Saturday, Jan 14, 2006 at 00:24

Saturday, Jan 14, 2006 at 00:24
Greetings

Basically for a vehicle to roll it needs to "trip". This usually occurs when a tyre deflates (more so with a front deflation) and the rim is able to dig into the surface in combination with a small lateral movement, causing the vehicle to "trip" (roll).

Front tyre deflation usually results in a tyre and rim separation combined with a wobbling of the wheel with the deflated tyre causing a turning action digging in the rim and causing the vehicle to "trip" (roll over)..

Firm grip on the steering wheel, stay away from the brakes, do not turn in the direction of the deflated tyre and no sudden deceleration. Adding power can enhance stability.

All of this is of course difficult to do when that front tyre suddenly deflates. Mostly the vehicle rolls.

Seatbelts, air bags and stronger modern vehicle structures make this type of accident more survivable providing, no solid objects are hit and the initial speed is not to high.

The higher the centre of gravity (CG) the easier this occurs. Hence 4WD's poor role over stats. Heavily ladden roof racks and overly high suspension lifts make this worse, causing big shifts in CG in an upwards direction.

Paul
AnswerID: 148465

Follow Up By: Member - Paul P (Bris) - Saturday, Jan 14, 2006 at 00:31

Saturday, Jan 14, 2006 at 00:31
Woops

"Firm grip on the steering wheel, stay away from the brakes, do not turn in the direction of the deflated tyre and no sudden deceleration. Adding power can enhance stability. "

Should be....

Firm grip on the steering wheel, stay away from the brakes, steer as straight as possible and no sudden deceleration. Adding power can enhance stability particularly at the point of initial instability. Decrease speed slowly.

Paul
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Follow Up By: geocacher (djcache) - Saturday, Jan 14, 2006 at 01:00

Saturday, Jan 14, 2006 at 01:00
Sorry Paul,

Blowouts or tyre deflations are a very seldom seen cause of rollovers. Granted they will cause what you describe but the I must have had a blow out excuse is one that seldom provides a plausable excuse.

This is possibly perpetuate by the number of vehicles that destroy tyres in crashes, thus providing an excuse after the incident - seems particularly prevalent in P platers.

The skid marks and the tracks in the grass or gravel often tell a far more accurate story about what happened in the seconds before the crash.

Most crashes occur as a result of driver error of some kind.

All of the international studies into crash cause & dynamics I've seen rate a failure of equipment as a cause in very low percentages (7% springs to mind but I've not got the stuff here now) of crashes.

Dave

Dave
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Follow Up By: Member - Paul P (Bris) - Saturday, Jan 14, 2006 at 01:24

Saturday, Jan 14, 2006 at 01:24
G'day Dave

Tyres do not have to deflate for a vehicle to 'trip" and roll. My comments use the deflated tyre as an example.

Vehicle defects, as you state, are a very low cause of accidents. "Human defects" are the top reason.

I flew into Brisbane today from Sydney. Watching the behaviour of my fellow humans ( motorists) as they set down and picked up passengers further re enforces the core issue of attitude to our motor vehicles. Until this is successfully changed I do not hold out much hope.

Regards

Paul
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Follow Up By: gramps - Saturday, Jan 14, 2006 at 07:44

Saturday, Jan 14, 2006 at 07:44
Paul,

Agree with you re attitude. The hardest of all contributing factors to rectify/change.
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Follow Up By: Shaker - Saturday, Jan 14, 2006 at 14:26

Saturday, Jan 14, 2006 at 14:26
Another way for a vehicle to "trip" is to increase the suspension travel, when it drops further than it is designed to do, the wheel tucks under & it will contribute to rollover.
Just ask anybody that has owned an early model Volkswagen Beetle!
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Reply By: Member - Phil G (SA) - Saturday, Jan 14, 2006 at 12:16

Saturday, Jan 14, 2006 at 12:16
Just another factor that contributes is when a load can move.

So with a large water or fuel tank, the fuel and water can slosh over to the downside, increasing the likelihood of rolling - naturally more likely the higher up it is.

And unsecured stuff on the roofrack can slide sideways having the same effect.

Cheers
phil
AnswerID: 148514

Reply By: Bob Y. - Qld - Saturday, Jan 14, 2006 at 15:49

Saturday, Jan 14, 2006 at 15:49
I'm surprised no one has mentioned wheel tracks, as a cause of roll-overs.

Dried wheel tracks, from previous wet weather events, have the potential to cause plenty of r'overs, if drivers suddenly drop a wheel into them. As mentioned above, the cause is probably blamed on tyre faults, after the event.

The addition of power steering, to modern 4wds, has probably saved a lot of people the hassles of a rollover.

Hooroo...
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Can't remember most of it.

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AnswerID: 148538

Reply By: ev700 - Sunday, Jan 15, 2006 at 23:43

Sunday, Jan 15, 2006 at 23:43
If you drive your softroader or 4WD like a car then you are very likely to have a rollover, especially if it is carrying more weight (incl passengers).

It is easy to oversteer in an apparently nimble softroader and it does not require a sudden tyre deflation to tip over. Most cars will weather over-correction or sudden direction change but specialist vehicles are not nade for that.

Quite apart frrom all of that, many the design requirements for off-road are contrary to those for stability and handling at speed.

Lesson: drive the fourby as a fourby - be more cautious of its limitations.

How long can car makers get away with linking speed to off-road vehicles? This is false advertising.
AnswerID: 148840

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