Out of respect to someone who has recently been thru a related drama, I hope starting a new topic is OK.
Have a look at Beginners intro to SUV Rollovers . To get an idea of what happens.
Or go to This place and have a look around .
Whatever! Unless something breaks, It's drivers and tyres (tires) that cause the upsidedownness of 4WD's!
Neil

OMG that first link was a dangerous, slanderous pile of steaming junk!

Eric,
Whats so bad about the first link? It actually made sense to me. I know
that it has been simplified, and may not model such things as coefficient
of friction, account for actual center of gravilty of each vehicle, but the physics
looks pretty sound. I agree that people need to realize that SUV's are more
prone to roll over by their very nature. People seem to think they are safer,
when in reality they would be saker in a regular car/van while saving lots
of money at the pump.

Lots of my neighbors and friends that have SUV's tell me they bought them
cause they look cool, and they dont want to be the typical parent in a mini-van.
They also never have been offroad, and have no idea on how their vehicle will
react in an emergency manuever. Also most of their SUV's dont even have 4X4
in them. WTF? Why have one in that case?

When I chose a primary car to transport my family I chose a van. Specifically
a Honda Odyssey. Great crash rating, good milage(24mpg), good power(210hp),
very comfortable, and somewhat stylish.

I also notice that most people (at least here in LA) drive their SUV's like maniacs.
Way to fast in residential areas(takes longer to stop a Suburban than a Camry),
tailgate you incessantly, and zip around the freeways like they are driving Ferraris.

Last observation: most speeding, cell phone talking, bad driving SUV people I have
had the pleasure to run accross or observe in my rear view mirror have been women,
that have their kids in the car with them <img border="0" title="" alt="[Mad]" src="images/icons/mad.gif" />
Not trying to women bash, just stating a personal observation.

</font><blockquote><font size="1" face="Verdana, Tahoma, Arial, Helv, Helvetica, Sans">quote:</font><hr /><font size="2" face="Verdana, Tahoma, Arial, Helv, Helvetica, Sans">Originally posted by Keven:
<strong>...most speeding, cell phone talking, bad driving SUV people I have had the pleasure to run accross or observe in my rear view mirror have been women, that have their kids in the car with them <img border="0" title="" alt="[Mad]" src="images/icons/mad.gif" />

Not trying to women bash, just stating a personal observation.</strong></font><hr /></blockquote><font size="2" face="Verdana, Tahoma, Arial, Helv, Helvetica, Sans">Yet they're anti-gun because guns are "dangerous" and they want to "protect the children". $h!theads... <img border="0" title="" alt="[Mad]" src="images/icons/mad.gif" /> <img border="0" alt="[Barf]" title="" src="graemlins/barf.gif" /> <img border="0" title="" alt="[Mad]" src="images/icons/mad.gif" /> <img border="0" alt="[Barf]" title="" src="graemlins/barf.gif" />

The thing I didn't like about that link is it seems to completely disgregard the existance of variables. Chaos. Reality.

"Using the specific dimensions of ANY vehicle, it is therefore VERY easy to quickly calculate at what speed it would roll over! No "expert" could possibly get away with testifying in court that he does not know!" - I completely disagree with this statement.

Dynamic roll, yaw rate of vehicle in curve, braking, accelerating, wind resistance, the driver crapping his pants (thus lowering his effective center of gravity), tire inflation pressure, tire brand and tread wear, age of tires (dry old rubber?) , passenger "rocking out" to music, road surface composition, humidity, that 50 pound subwoofer box in the back, driver input on steering wheel, brand and condition of shock absorbers, condition and composition of sway bar bushings, amount of play in wheel bearings....

eh, you get the point.


Math gives you a good starting point but no matter how many times you look at it on paper, "sh*t happens" .

People should count their blessings and get on with their lives.

note: if there is actual negligence... as in, cutting corners or deceiving buyers or whatever... sure, good, look for it and try to bring some good out of it by exposing the truth. But cars are engineered pretty safely these days. Safer than cars 60 years ago with regards to rollovers anyhow. Safer than taking a 1700's wagon train the same distance we drive cars these days.
An inevitable fact of life is that people die.

<small>[ February 21, 2003, 03:24 PM: Message edited by: Eric D ]</small>

It is a good study .... except for the 7200 lb side force. To get that from a 3200 lb vehicle you need a friction coeficant of greater than 2.

Not likely to get much past .8 so in a static (constant turn) condition the vehicle could not roll over since less than half of the calculated force could be generated.

Its a good start at looking at how things work but it makes a very bad initial assumption.

Kevin C

<small>[ February 21, 2003, 04:17 PM: Message edited by: Kevin C ]</small>

Oh commoooon Remember what a study use t say about the GEN III roll over danger at even 35 MPH? I once had to do the same emergency maneuver at 75mph and it couldn't be safer and in absolutelly total control. GEN III is one safe SUV, I can take a curve at 75 MPH, the same that in my 88 I have to take at 45mph

Well, I was once a high school physics student, and I've also built roads. This assumption is the root of a fatal error is this goof's analysis: </font><blockquote><font size="1" face="Verdana, Tahoma, Arial, Helv, Helvetica, Sans">quote:</font><hr /><font size="2" face="Verdana, Tahoma, Arial, Helv, Helvetica, Sans">For this example, we will consider a vehicle turning in a circular course, to the right, approximately like circling clockwise in an intersection, with a circle radius of 20 feet. </font><hr /></blockquote><font size="2" face="Verdana, Tahoma, Arial, Helv, Helvetica, Sans">The almost universal standard for a residential, thoroughfare, or arterial intersection for the radius to BACK OF THE CURB is a radius of 25'. To turn with a radius of 20' means you're off the pavement on the inside of the curve with ALL FOUR WHEELS! To attempt a turn in a right angle corner at 25mph is total driver insanity, and you deserve to die. KevinC makes another salient point about the coefficient of friction. F1 cars get insanely high coefficients of friction by artifically increasing their downforce with aerodynamic aids like wings and specially shaped underbodies that push or suck the car to the pavement. In the late 60's, Jim Hall's Chapparals used a second engine to run a fan to suck the air from under the car, and contained that vacuum with ground rubbing skirts, to achieve the same effect. The dunce uses what looks like a sane speed of 25mph in his example, but as he says in his first paragraph (though clouded in disguise of other problems you "might" - translate as would - encounter as you entered the inevitable slide) an unintended off road expedition is in your future, probably followed very shortly by an instantaneous decelleration caused by a fixed object.

The suv would most likely understeer right thru the intersection, rotating slowly to the right, until the wheels encountered a curb or soft dirt and did in fact roll, all because of the initial driver error of too much speed for the corner.

I was in a hurry, pushing the FJ55 Cruiser (a VERY top heavy beast) down an unfamiliar road in the dark. I entered a corner at what appeared to me to be a high but doable speed, and the corner turned out to have an off camber (tilted to the outside) decreasing radius (gets tighter as you go around). The fronts broke loose first, and I came off the power and dabbed the brakes to transfer weight to the front to get some bite, and as the rears unloaded in that maneuver, they broke loose, and I slid 3/4's sideways around the corner, staying on the pavement all the way. My tires were properly inflated, so they kept thetread on the road instead of rolling it under and losing most of their bite or tearing off the bead and digging the rim into the asphalt.

I'm sorry, but all this is too reminiscent of the Audi "unintended acceleration" cases, where idiots mashed the gas instead of the brake, and claimed the car just "kept going faster no matter what I did".

I have said before and I say it again. If you roll your SUV, it's YOUR FAULT. You didn't keep your tires aired up, or you drove it too fast for conditions or the maneuver attempted, or you failed to properly anticipate the stupidity of those on the road with you, and didn't keep an escape route open. If that hurts your feelings, it's too damn bad. "To suffer ove the sensibilites of fools is to be a fool yourself." Maybe you'll quit driving and I'll have one less idiot to worry about.

Well put, fasteddy - and thanks for having the balls to disregard political correctness in favor of the truth. We need more of that.

Well put Fasteddy.

The 20' radius turn is probably not a very appropriate example, HOWEVER it may carry a bit of weight for the emergency evasive manoever (very quick steering input combined with heavy braking). The one weakness of the original article is that it did not take into account braking and the resultant transient weight distribution changes on the wheels/tires. This would tend to potentiate the effects he described. (who hasn't "fishtailed" on loose surfaces?)
There is actually an argument for turning into the direction of the slide with a dab of accelerator (ON LOOSE SURFACES ONLY) to regain control. Just ask any rally driver about "Heel and Toe" cornering and flicking the tail out prior to the corner.

Note: I do not endorse these rally techniqes on public roads. Speed should never be a factor in recreational 4x4ing.

<small>[ February 24, 2003, 06:21 AM: Message edited by: GaryInOz ]</small>