Toyota Prado

Hi Robin Miller. I am interested in info you have unearthed as to the stability of the Prado. It doesn't surprise me to hear that it not stack up against, say, the Patrol, espeially for lateral stability.
My point is that, yes, I own a 90 series Prado (GXL model, so a bit wider, perhaps, than the base model), and yes, it has a 2" lift, and, yes, it has an aluminium roof rack. So how 'bad' it my vehicle? I am NOT about to have a go at you, but keen to draw on your knowledge.
Any commets? thanks.

Hi TenPounder

On a day when our news broadcast have said the government is considering mandatory electronic stability be fitted to cars its sobering to review rollover stats in 4wds.

Rollover stability is a massive poorly reported issue in this field
and its a little disconcerting that no figures tilt table are pubished to my knowledge on the 120 series, espically by Toyota.
I think some 50% of deaths in american SUV's are now from rollovers.
Toyota have a figure of 45 degrees on the 100 series Cruiser and Nissan 48 degrees on the patrol , not near my library at the moment but I think its about 43 for your 90 series
from RACV tests (They no longer do tilt table tests).

I first got concerned, must be a decade ago at the launch when I test drove one at Angelsea proving grounds, which included a side slope test.
She's a high and narrow car but since then the track width has increased a bit from I think from 1505/1510 to 1575/1575 with the new model.

Its worth pointing out that while in the lower end of rollover performance they can be a good viable car for many if not pushed, and I admit I mostly drive in victoria with lots of big and steep muddy hills.

I'd look at keeping your front shocks in top order, stacking the weight down low and in front of the rear axle, and perhaps removing the lift and adding more underbody protection to compensate.

I note that rear wheel spacers are a hot selling item for the new troppy type cruisers , but I think if fitted to a Prado that the wheels would hit the guards, and this makes it hard to do anything fundamental to improve the car.

Thank you, Robin Miller for your comments. It is perhaps food for thought that I have made things worse in terms of static roll angles by adding stiffer (as well as longer) springs, but this may have improved the dynamic lateral stability (less lurch).
It is an issue for all of us that a bit of soft stuff on the downhill side (eg topping a dune in the Simpson and turning sharp right as one has to) could easily cause problems when there's a bit of weight on the roof rack.
Thanks again for your contribution to our understanding.

Robin [and others] you need to be careful quoting 45 degree and higher rollover figures. In many cases the manufacturers spec actually says 45%. This is 45% of 45 degree or 1 in 1.
When you consider a 45 degree angle you will see that very few vehicles could ever remain upright on this slope. To my knowledge the only vehicle that could remain upright on 45 degrees was a series 1 Landy. I say a pic once of the Rover factory test with a series 1 shorty soft top sitting on a steel plate. There is no way known any modern wagon would remain upright on a 45 degree slope.
Ken

Hi Ken

No problems , I'm well up on the engineering side of things in these matters.

It is 45 degrees not 45% and the 100 series landcruiser brochure I have in front of me here even has it in a little picture form in degrees.

The RACV tests used the seymour military faciliy and completely document the process.

Robin, simple physics says once the centre of gravity falls outside the object envelope it must fall. This is because the vertically acting component of the vehicle mass is greater than the horizontal component. If you look at an object on a 45 degree slope, take the simple case of a square box. Put a dot in the centre of the box representing the centre of gravity of the object, draw horizontal and vertical lines to the slope; you will find they are of equal length. Now put the dot a few mm above the centre of the object and see the difference in the length of the lines and where the vertical line meets the slope. It is outside the envelope of the object and longer then the horizontal line. The lines represent the forces acting in the vertical & horizontal planes, the force down is larger than the force horizontally so the object tips.
A Toyota brochure [or any other vehicle manufacturer's] is hardly a scientific or engineering document and I remain unconvinced that a 100 series would a) not slide off , or b) not tip on a genuine 45 degree slope.
Ken

Hi Ken

Your reply introduced a different point "Slipping".
Slipping sideways is not part of the tilt table test as this depends on the co-efficent of friction between the tyres and ground - on ice every car slips sideways at even a few degrees.

In actual fact almost every standard car like commodores and falcons exceeds 45 degrees its only the 4wds that don't generally make it and average out at 40-45.

The following link may convince you.
It shows tilt angles for vehicles modified for police work , yet even
with the extra gear the cruiser comes in at 42.2 degrees, and further reading of this Monash university report shows that Nissan Patrols are a lot better, and troppies as a disaster.

http://www.monash.edu.au/cemo/roadsafety/abstracts_and_papers/054/roadsafety%20conf%20police%20paper_revised.pdf


Unlike the square box you described which has an even density distribution a vehicles roll point is expressed by its Static Stability factor. (track width/ 2 * C of G).
These figures are required by law in USA and are publically available, and are almost all above 1.

Ian
Lokk at this. http://www.safarisnorkel.com/dtronic/dtronic.htm

They are available and fitted by ARB among others.