05-Aug-2012 13:39:55
- Atzporsche
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05-Aug-2012 13:58:22
- REALZEUS
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05-Aug-2012 17:47:06
- REALZEUS
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Re: Jeep Grand Cherokee - Moose test
Atzporsche:
We're talking about general off-road use by some bloke in the mountains not going on a Dakar with a stock setup.
I have been to places with my Landie that an ML wouldn't dream of. Yes, it is slow and cumbersome on the paved road, but those solid axles and them 3 diffs with a 3.7:1 low gear ratio, coupled with 25 cm minimum ground clearance below the ladder type chassis make it unbeatable off the tarmacadam really! 
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Re: Jeep Grand Cherokee - Moose test
fritz:
GM Austin:
Atzporsche:
How did they manage such a shitty behavior.. the chassis is from Mercedes and their car has no such issues.
The design objective is different. As I said previously, a good off-road suspension is a horrible on-road performer. Jeep advertises that all their vehicles are Rubicon tested, or something like that. Meaning their vehicles can navigate the Rubicon Trail, or any other similarly rugged terrain. High ground clearance is one thing that is required, which will give the vehicle a higher center of gravity (not desireable for on-road). The next thing is wheel articulation. In order to maintain contact with the ground when the ground is very uneven the wheels need the freedom to move very independently from one another from left to right so that you can maintain traction. If you are climbing a hill and the left wheel has to go over a large rock, you don't want the right wheel to come off the ground because of that. You want the right wheel to maintain contact with the ground so you don't lose traction and the vehicle slide backward. This means the anti-roll bar needs to be smaller in diameter than what would normally be recommended for good on-road performance. The off-road desireable feature of the left and right wheels having good independent verticle movement is exactly counterproductive to good on-road performance, as we see in the video. Severe body lean when cornering is a fact of life for the off-road tuned suspension. Correcting the bad on-road manners will compromise the off-road ability. Jeeps and Land Rovers are both good off-road performers and both suffer from serious body lean when cornering at speed. If they take a model and alter it for good performance on the pavement (a Range Rover model comes to mind), one of the things they will do is increase the roll-bar diameter, reducing body lean when cornering, but also reducing the left/right independent whell movement and compromising the off-road ability.
The argument that a car cannot handle the Rubicon Trail and fast highway driving with equal competence is naturally valid. Too many concessions have to be made to real off-roading characteristics for a car like the Grand Cherokee to have sharp sports car handling. "Rubicon Tested" may sound good in the ads, but its not really what about 95% of the car's buyers should really be looking for considering the use they will put it to.
I just think after watching that video that, to my non-expert eyes:
a) the ragged transitions in attitude of the vehicle in the slalom stretches suggested that not enough work had been put into fine-tuning the ESP system to allow the transitions to be smooth and more controllable, at least in the hands of experienced drivers like these test drivers, and
b) a better choice of wheels (widths?), tyres and recommended pressures would reduce the risk of the side walls being pinched between rim and asphalt causing immediate blow-outs with possibly disastrous consequences, as happened to 6 of the 7 cars tested in this case.
These two measures would add a little to the development budget and probably to the production cost of the vehicle, but would not necessarily detract from its ability to negotiate the Rubicon Trail.--
fritz
Absolutely agree. There are many tools available to mitigate the on-road dangers of the off-road tuned suspension. ESP or some similar electronic stability program should be able to prevent most disasters. In the case of the Jeep I think most of the problem is sloppy engineering. As you note, simple things like different tire or wheel selection might prevent the tire blowouts in the near rollover situation.
07-Aug-2012 15:22:39
- Atzporsche
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Re: Jeep Grand Cherokee - Moose test
The Jeep is certainly victim of shitty inhouse engineering.. Funny when it came out, it went to see it at the dealer and thought wow finally a good American car based on a proper MB chassis. I thought this thing will rock both on the road as well as off-road. Seems they really went cheap on the development and the result is a pretty bad handling car.. 
08-Aug-2012 16:28:07
- Joost
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09-Aug-2012 02:23:44
- skazzy
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Re: Jeep Grand Cherokee - Moose test
Atzporsche:
How did they manage such a shitty behavior.. the chassis is from Mercedes and their car has no such issues.
While the 2 may share the ML chassis, the suspension setup is very different. The Jeep uses a primitive live axle while the MB uses a far more complex system which can adjust power being sent to each wheel.
Re: Jeep Grand Cherokee - Moose test
Porker:
Terrifying results imo.
http://www.youtube.com/watch?feature=player_embedded&v=zaYFLb8WMGM
According to german Auto, Motor und Sport, the video is...crap. They didn't respect the official "moose test" criteria, the car was overloaded. AMS tried to re-create this disastrous moose test but the Jeep Grand Cherokee didn't show any particular issues (they tested the Jeep Grand Cherokee before the Swedish test and even then, no issues). AMS used the official moose test criteria which requires a specific track (friction) and test track width.
Just saying...
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