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  #49  
Old 07-20-2012, 11:37 PM
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Re: Jeep Grand Cherokee Moose Test -- Full Story

What sunvisor has that ? My Laredo just has a airbag warning.

Also if I were going to autocross, I'd have the tires at their max 51 psi inflation, not the recommended 33. On my Sunbird when I started running 50 psi in front, I started having to avoid inside pylons.

Is a simple fomula: the tires have a max load at a certain psi. Mine are 2205 lbs at 51 psi. In a very hard corner I figure all of the load is on the outside tires (have been known to carry front tires over speed bumps on an apex). My V-6 Laredo weighs around 4400 lbs distributed (see the specs) about 50/50 so 2200 on each end. Ideal pressure then is 51 psi X 2200 lbs/2205 rating = 50.8 psi.

Let's just say if in Moose country and there was the possibility of needing evasive action, I'd bump up the stock tire pressures a tad.

ps I have been known to break wheels (usually the right front) in an autocross but never had a flat tire. Real racing now...
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  #50  
Old 07-21-2012, 08:27 AM
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Re: Jeep Grand Cherokee Moose Test -- Full Story

Im pretty sure these test are designed to find what kind of trouble an incompetent driver can get into and then hurt others. They are designed to set up the vehicle the worst it can handle but also within the manufacture's specification... and then do dumb things.
Something like this video:




My wife does not know tire psi from slip angle or the price of bread. But she does know which grocery store happens to have the best value...
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  #51  
Old 07-21-2012, 08:48 AM
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Re: Jeep Grand Cherokee Moose Test -- Full Story

That 4runner is a 10-15 year old vehicle, before the prevalence of stability control systems. There is no reason a 2011/2012 vehicle should act this way. This is something Chrysler should have fixed rather than trying to slam the magazine that did the testing. A similar problem was discovered with the Lexus GX460 by CR and Lexus stopped sales and fixed the problem. Yes ordinary people do not do this with vehicles on a regular basis, but the one day when you need the car to handle under stress it can be a life or death difference.
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  #52  
Old 07-21-2012, 09:45 AM
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Re: Jeep Grand Cherokee Moose Test -- Full Story

Obviously I'm no expert but I don't see a electronic fix for this problem. It seems the air suspension acts like a childs bouncey house and literally rebounds or trampolines the Jeep off it's wheels. Wheelbase, weight, ride height, center of gravity, etc also play their role. How do you fix that? The Jeep guys tried to fix it by getting the car to max payload trying to keep the car down. Maybe sandbags? Will decrease your MPG but keep you planted on the road

It is possible Jeep screwed up the stability control parameters and they simply don't work. Heck, my TPMS fuse blew and still was registering normal pressures on the wheels.

I would like to see a 2012 ML 350 with air suspension and see how it does. To me, that would be very interesting since the cars share quite a few things.
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  #53  
Old 07-21-2012, 09:56 AM
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Re: Jeep Grand Cherokee Moose Test -- Full Story

Quote:
Originally Posted by mpatel1080 View Post
That 4runner is a 10-15 year old vehicle, before the prevalence of stability control systems. There is no reason a 2011/2012 vehicle should act this way. This is something Chrysler should have fixed rather than trying to slam the magazine that did the testing. A similar problem was discovered with the Lexus GX460 by CR and Lexus stopped sales and fixed the problem. Yes ordinary people do not do this with vehicles on a regular basis, but the one day when you need the car to handle under stress it can be a life or death difference.
The "problem" CR found was that the GX460 had a sportier ESP tune. One that would allow you to enjoy its V8 a little bit. It only could have presented a problem if you were a moron and enjoyed it sideways into a curb, which then maybe would have flipped it.

The "fix" was to make the ESP much more obtrusive and make it no longer any fun.

Truthfully, about the only things that would affect the performance in this test would be:
1) When the ESP program comes in, make the steering input matter less so the guy can't overcompensate
2) When the ESP comes in, just full force brakes to stop the vehicle (potentially with option 1 as well)
3) Adjust the dampeners, such that they dissipate the angular force faster

I'd like to see an ML550 do the test as well.

It was my understanding that Jeep tried ot fix it by taking weigh OUT. The Swedes overloaded it, then Jeep was like "nuh uhn", removed weight, then it started popping tires. Which isn't surprising, the stock tires are Goodyears and not so great. Heck, the GYs aren't even XL rated sidewalls.

I'd like to see the same test done on the Jeep with a decent set of tires. Or more importantly to me, with Nitto Terra Grappler ATs.
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  #54  
Old 07-21-2012, 10:45 AM
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Re: Jeep Grand Cherokee Moose Test -- Full Story

Careful what you ask for. With the elecrohydraulic steering it would be possible to limit the steering rate to avoid the harmonic (what caused the bouncing).

I am curious whether a GC without the QL would act the same way.

BTW a 265x60x20 seems to have a load rating of 2100 kbs, 100 lbs less than the Laredos 17s and 200 lb less than the Limited's 18's.

Tire pressure gets a little confusing. According to TireRack a "standard load" tire is measured at 36 psi (my Goodyears are stamped "Standard Load"). The doorjambs are marked "33 psi".

Goodyear gives an idea of load rating vs psi on page 7. In simpler terms the load rating drops about 2.5% for every psi underinflated.

Finally the 4X4 Hemi is not 50/50 like my Laredo and weighs closer to 5400 lbs so the load on the front tires is more like 2900 lbs than 2200.

So a 20" tire rated at 2100 lbs and say 3 psi underinflated (what does the door jamb sticker for the 20" option say about inflation pressures please ?) with both cornering forces, and forward weight transfer, and loading from the harmonic (bounce) all on the front tire which is turned and you see that the forces on that front tire are A Lot.

Finally, I can see pylons set up that way at an autocross but for a moose I have to question if that sharp a turn back is necesary. Are we to assume an oncoming Semi ? Can see the sharp initial turn if a moose or tree jump out in front of you, then a correction to stay on the road, but why would someone make that sharp turn back afterwards. To me that is the piece that is unlikely.

So I agree the test does demonstrate stability and could see it in an autocross (though few clubs have that many pylons) but the final section is just not real world IMNSHO.
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  #55  
Old 07-21-2012, 10:59 AM
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Re: Jeep Grand Cherokee Moose Test -- Full Story

Quote:
Originally Posted by mpatel1080 View Post
That 4runner is a 10-15 year old vehicle, before the prevalence of stability control systems. There is no reason a 2011/2012 vehicle should act this way. This is something Chrysler should have fixed rather than trying to slam the magazine that did the testing. A similar problem was discovered with the Lexus GX460 by CR and Lexus stopped sales and fixed the problem. Yes ordinary people do not do this with vehicles on a regular basis, but the one day when you need the car to handle under stress it can be a life or death difference.
So you are saying manufactures should take the driving away from the operator and go to full robotic and automatic control... perhaps dumb it down so a 6 year old is safe in the operator's seat... certainly safe, but what fun would that be? It takes a skillful driver to place the vehicle in that test situation, a skill 99% of us don't have even if we had the reaction time. Those of us with the skill know better...

PS, Youtube is full of roll overs, some pretty funny. There is also a video where they drove a focus at 120mph into a wall just to see how safe it was. It failed! Imagine that. Perhaps Ford should limit the speed of those things to like 40mph, now that would save a lot more lives than ESP in a moose test. Lets fix the problems that really effect us, not the .01 % outlanders

Oh wait, politically its probably best to attack/offend only .01% of the voters. Just saying there is a fuzzy line here, plenty of places Jeep could be spending their time beside this self-serving sensationalism stuff. Take it as a data point and move on. Something to be learned here. The moose test is about as extreme as hitting a wall at 120mph, oh maybe exaggerated, perhaps 80 mph. Vehicles are capable of reaching those speed you know. If you don't think manufactures should fix the 120mph problem, then how can you demand a fix for the moose test? Swerving into a lane with oncoming traffic is about as dumb as traveling 120mph on a public road, in my opinion.
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  #56  
Old 07-21-2012, 12:40 PM
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Re: Jeep Grand Cherokee Moose Test -- Full Story

Quote:
Originally Posted by FAUEE View Post
It was my understanding that Jeep tried ot fix it by taking weigh OUT. The Swedes overloaded it, then Jeep was like "nuh uhn", removed weight, then it started popping tires. Which isn't surprising, the stock tires are Goodyears and not so great. Heck, the GYs aren't even XL rated sidewalls.
These might be Continental tires, not Goodyears. I believe the export models get Kumhos and/or Continentals instead. A good test, would be to equip the same vehicle with different tires on the 20" wheels and see if it behaved similarly.
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  #57  
Old 07-21-2012, 05:36 PM
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Re: Jeep Grand Cherokee Moose Test -- Full Story

Guys you need to understand the testing parameters that the tester used.
They went off the JEEP maximum weight loads and tyre pressures, they did not make up their own figures, there were OFFICIAL figures that Jeep supplied to approve the Jeep in the EU.

Apparently it was revealed after, that Jeep under quoted the weight by 158kg. This means that the test was done according to the specs given by Jeep, but in reality it was overweight by 158kg. This is why Jeep took out weight for the 2nd test, where the tyres just blew out.

As for the ESP, it is a serious worry the way the car acts in this test. ESP does not require the driver to activate the brakes, for the ESP to brake the wheels. This is the big advantage of ESP over ABS. ESP is designed to keep the car pointing in the direction the drive needs it to, regardless of the conditions. This allows a driver to steer around a potential crash, rather than just skid into it. The system also has rollover mitigation that is designed to stop the car from getting into a potential rollover profile.

This test reveals that the ESP cannot cope with the conditions that it has been presented with. If you search "Moose Test" on Youtube, you will find several examples of cars that have failed this test. Ironically most do not have ESP fitted. The JGC behaves very much like a car without ESP. It is possible that the extra weight overwhelms the ESP and it just does not react.

There is no point in criticising the test or trying to discredit the scenrio, the fact remains that this test has shown a serious safety issue with this car in a plausable test at a relitave low speed.

This is totally unacceptable for a 2011+ vehicle with all the safety stars and features that has been claimed by Jeep. Regardless of the weight, tyres fitted, testing scenario or any other excused, it is UNACCEPTABLE.

You can either accept the results and demand Jeep address this, or you can keep living in denial and just live back in your alternat reality.

Jeep need to put out either an official statement and what they plan to do to fix it, or provide some proof that there were serious flaws in the test and show us why we should believe them.
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  #58  
Old 07-21-2012, 05:52 PM
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Re: Jeep Grand Cherokee Moose Test -- Full Story

Are there a few Mooses about on the Sydney Harbour Bridge at this time of the year?
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  #59  
Old 07-21-2012, 05:53 PM
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Re: Jeep Grand Cherokee Moose Test -- Full Story

Or just not have underinflated/undersidewalled tires. Personally am happy with 17s on 8" rims and a Heap that weighs 1/2 ton less. Would be interesting to see how a 2WD V6 Laredo does in the same situation. Of course I don't think they sell those in Sweden.

ps one of the most valuable lessons I learned for SCCA racing was "slow hands". Perhaps we should be teaching that.
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Old 07-21-2012, 05:59 PM
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The Jeep hardly comes close to rolling over. Watching other videos of failures those cars get up high on two wheels or flip. I'll tell you what. Once someone rolls their Jeep then I'll listen.


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