31" Tires

[Oyaji]

The Compass and Liberty KJ had 17" and 18" factory 5 x 4.5" wheels for certain years. No idea on the BS though.

 

 

Good info though, had never heard of the 18" offering. Knowing what they came on narrows down the search - thank you. Still need to find the backset and the width - if anyone here can contribute, sing out!

 

18" wheels with 31" tire diameter would give a 6.5" sidewall - plenty to prevent wheel damage, and would cut down on "tuck" during cornering (admittedly not a strong point of a truck, but you never know when you might be forced into drastic maneuvers). Some of you might think I am too mindful of safety... seen this? ;)

 

[mvusse]

It's a Jeep. With the higher ground clearance to go off road comes a higher center of gravity. I would as soon buy a Grand Cherokee to do a slalom in a parking lot as I would a C30 to go to a hunting shack 5 miles off road.

 

We can test the C30 off road against a Grand Cherokee, Trailblazer, Mercedes G class, Range Rover and others and claim the C30 is utterly useless, and warn people not to buy one if they want to be able to go where they want.

[Oyaji]

It's a Jeep. With the higher ground clearance to go off road comes a higher center of gravity. I would as soon buy a Grand Cherokee to do a slalom in a parking lot as I would a C30 to go to a hunting shack 5 miles off road.

 

We can test the C30 off road against a Grand Cherokee, Trailblazer, Mercedes G class, Range Rover and others and claim the C30 is utterly useless, and warn people not to buy one if they want to be able to go where they want.

 

 

Didn't even realize it was a Jeep. Example was not a "slalom", but just a simple avoidance maneuver, and only at 43 mph at that. Safety applies to vehicle type regardless of make and model.

 

There are some pretty simple things that can be done to improve vehicle dynamics - among them tire and rim choice and inflation pressure.

 

Would you prefer a Ford example?

[Eagle]

 

The Compass and Liberty KJ had 17" and 18" factory 5 x 4.5" wheels for certain years. No idea on the BS though.

 

 

Good info though, had never heard of the 18" offering. Knowing what they came on narrows down the search - thank you. Still need to find the backset and the width - if anyone here can contribute, sing out!

 

18" wheels with 31" tire diameter would give a 6.5" sidewall - plenty to prevent wheel damage, and would cut down on "tuck" during cornering (admittedly not a strong point of a truck, but you never know when you might be forced into drastic maneuvers). Some of you might think I am too mindful of safety... seen this? ;)

 

 

I hadn't seen that one, but I do remember the original Liberty failed one magazine's slalom test in spectacular fashion by rolling over. That led Jeep to cancel the Up Country version of the Liberty until they could re-engineer the shocks and spring rates.

 

That said -- a Jeep isn't a sports car. I am concerned about safety, but I have no illusions that any of my XJs or MJs will ever be the equal of my race-prepped Javelins or AMXs on a road course. I will comment that I once put the 2000 XJ Classic into a full lateral power slide at 60 MPH when some idiot cut my off on a highway. IMO the problem now is that Jeep has a newer generation of engineers, whose priority seems to be to make the vehicles "look like Jeeps but ride like limousines." Something has to give when you try to combine mutually exclusive goals, and it seems that Jeep's compromise has been to give up safety and handling.

[Oyaji]

I do remember the original Liberty failed one magazine's slalom test in spectacular fashion by rolling over. That led Jeep to cancel the Up Country version of the Liberty until they could re-engineer the shocks and spring rates.

 

That said -- a Jeep isn't a sports car. I am concerned about safety, but I have no illusions that any of my XJs or MJs will ever be the equal of my race-prepped Javelins or AMXs on a road course. I will comment that I once put the 2000 XJ Classic into a full lateral power slide at 60 MPH when some idiot cut my off on a highway. IMO the problem now is that Jeep has a newer generation of engineers, whose priority seems to be to make the vehicles "look like Jeeps but ride like limousines." Something has to give when you try to combine mutually exclusive goals, and it seems that Jeep's compromise has been to give up safety and handling.

 

Once again I reiterate that the first video was not a slalom, but rather a simple avoidance maneuver. Additionally, 2 other vehicles from similar class(VW Touareg and Volvo XC90) easily managed to pass the same test the Jeep failed - and the Grand Cherokee has not only front and rear independent suspension but also active stability control.

 

I do take your point about Jeeps not being sports cars, and I completely agree. Vehicles with beam axles are far worse than the Grand Cherokee tested - but if it failed with IFS and IRS plus stability control, what sort of chances would an old Jeep have? Compound that with lift and ask yourself that again...

 

I disagree that the trend is toward giving up "safety and handling" - quite the contrary I think. The manufacturers had a good run of getting away with just short of outright murder for years, but ever since the Ford Explorer debacle (liability for which - in my opinion -  they successfully but unjustly were able to pin on Firestone tires) there has been pressure to develop safer high-profile vehicles. Active suspension stability control, independent suspensions, and lowered profile have all been part of the move toward safety over the past 10+ years.

 

I don't want to sell short the appeal of beam axle suspension for off-road capability; in fact I am a proponent of keeping road certification for such vehicles no matter how extreme. But it is incumbent upon the drivers of such vehicles to exercise due care to operate them in a safe manner. For myself, I prefer to be able to keep up with average traffic, and so I seek all the edge I can reasonably muster in making my vehicles as roadworthy as possible while expanding somewhat the off-road capabilities I am able to enhance.

 

I will remark that most of the level of safe operation capability that a given vehicle has is derived directly from its operator. I know a little of your background and so I can comment that many (most?) drivers in the emergency avoidance anecdote you related would not have fared so well as you did. Here is an anecdote of my own... A company I used to work for paid to have key personnel attend a 4-day Bondurant racing course so as to improve their driving capabilities on the test track (thus enhancing not only the safety of the personnel but also of the hand-built multi-million-dollar prototypes they drove!). At the end of the 4-day course just before "graduation", Bob Bondurant loaded a 12-passenger Ford Econoline van full of his driving course students and challenged them one at a time to pass him in his heavily-loaded van on a road course while the student drove a competition open-wheel race car. To my knowledge, no one ever beat that challenge. That illustrates what used to be a maxim of car design: "any properly-designed vehicle will always slide before overturning." Some SUVs of the 1980s/1990s pushed (some would say violated) that.

 

Here is another anecdote: Christina Hefner, publisher of Playboy Magazine (and daughter of Hugh Hefner, founder) once remarked that "there are 2 things every red-blooded American male thinks he can do better than any other - and 1 of them is drive."   :rotf:

 

Anyway, the upshot is that no matter how good I may think I am, I am always looking for an edge to do better. My experience has made me more a stickler for safety than most folks, but as those folks who have built cars from the ground up know very well, there is more than one measure of performance.

[Eagle]

Oyaji, I speak (okay, I write) not as a professional engineer (which I am not, although my education leading up to a master's degree in architecture necessarily included structural and mechanical engineering) but as an automotive enthusiast who has built and raced his own SCCA-legal pony car (1968 Javelin) and driven old military Jeeps, Cherokees, and Comanches both on- and off-road. I agree with you 110 percent about safety, which is why the first question I ask here when someone wants to lift their MJ is "Why?" The goal, IMHO (an opinion shared with any number of off-road experts) is to lift the vehicle as LITTLE as possible to enable it to go where you want to go. Any lift beyond the minimum necessary is wasting money, and making the vehicle less safe.

 

That said, the bean counters at Jeep have decreed that they want to appeal to a wider spectrum of buyers. That means buyers who would not previously buy a Jeep because ... well, because it rides like a Jeep. It's not just a question of switching to independent suspension on all four corners. It's also things like spring rates, shock absorber valving, suspension geometry, steering ... a plethora of interrelated factors that all affect ride comfort, stability, maneuverability, and safety. The first Liberty was Jeep's first (modern) independent suspension vehicle, and it tipped over in a slalom course that previous, solid axle Cherokees had passed. That tells me something.

 

I also know that when Jeep introduced the then-new 1999 Grand Cherokee (the WJ), they had to recall the export suspension due to some problem. IIRC (which is open to question at this point), the fix involved changing both spring rates and suspension bushing durometer specs. Again, to me this is indicative that even 14 years ago Jeep was already trying to make Jeeps ride like ... unJeeps. Your reference to the Ford debacle was another example. The problem wasn't the Firestone tires -- the problem was that Ford wanted what was basically a truck to ride as soft as a car, so Ford specified an insanely low tire pressure (contrary to Firestone's advice), and then Ford blamed Firestone when the tires began to explode due to [entirely predictable] overheating.

 

I have no doubts that my wife's or my 2000 Cherokee would have no problem negotiating the evasive maneuver in the video you showed. The fact that a new Grand Cherokee failed so spectacularly simply confirms (for me, at least) my belief that Jeep is no longer building Jeeps.

[mvusse]

One thing top note about the Liberties, the things weight about 1000 pounds more than Cherokees.

[Oyaji]

mvusse, on 17 Nov 2013 - 16:37, said:

One thing top note about the Liberties, the things weight about 1000 pounds more than Cherokees.

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They're taller, too. Not only does that adversely affect vehicle dynamics, it bites into fuel economy by increasing the frontal area.

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You just hit a nerve about why I almost-but-not-quite ever got to liking the Liberty. :)

[Oyaji]

Oyaji, I speak (okay, I write) not as a professional engineer (which I am not, although my education leading up to a master's degree in architecture necessarily included structural and mechanical engineering) but as an automotive enthusiast who has built and raced his own SCCA-legal pony car (1968 Javelin) and driven old military Jeeps, Cherokees, and Comanches both on- and off-road. I agree with you 110 percent about safety, which is why the first question I ask here when someone wants to lift their MJ is "Why?" The goal, IMHO (an opinion shared with any number of off-road experts) is to lift the vehicle as LITTLE as possible to enable it to go where you want to go. Any lift beyond the minimum necessary is wasting money, and making the vehicle less safe.

 

That said, the bean counters at Jeep have decreed that they want to appeal to a wider spectrum of buyers. That means buyers who would not previously buy a Jeep because ... well, because it rides like a Jeep. It's not just a question of switching to independent suspension on all four corners. It's also things like spring rates, shock absorber valving, suspension geometry, steering ... a plethora of interrelated factors that all affect ride comfort, stability, maneuverability, and safety. The first Liberty was Jeep's first (modern) independent suspension vehicle, and it tipped over in a slalom course that previous, solid axle Cherokees had passed. That tells me something.

 

I also know that when Jeep introduced the then-new 1999 Grand Cherokee (the WJ), they had to recall the export suspension due to some problem. IIRC (which is open to question at this point), the fix involved changing both spring rates and suspension bushing durometer specs. Again, to me this is indicative that even 14 years ago Jeep was already trying to make Jeeps ride like ... unJeeps. Your reference to the Ford debacle was another example. The problem wasn't the Firestone tires -- the problem was that Ford wanted what was basically a truck to ride as soft as a car, so Ford specified an insanely low tire pressure (contrary to Firestone's advice), and then Ford blamed Firestone when the tires began to explode due to [entirely predictable] overheating.

 

I have no doubts that my wife's or my 2000 Cherokee would have no problem negotiating the evasive maneuver in the video you showed. The fact that a new Grand Cherokee failed so spectacularly simply confirms (for me, at least) my belief that Jeep is no longer building Jeeps.

'

Okay, I take your point about Jeeps. I was speaking more generally about the industry.

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Thanks for sharing some more of your background. You are quite right to zero in on spring and swaybar rates, shock valving, and even suspension bushing durometer, and to point out that there is more to vehicle dynamics than whether a suspension is beam axle or independent. (Surprised you did not mention unsprung weight though, nor the most important factor of all: position of the roll center in relation to the center of gravity. ;)) I didn't know that the Liberty was rollover prone from the factory, either - that speaks directly to the maxim I mentioned earlier, that "any properly-designed vehicle will slide before it rolls over." (I just remembered who said that - Dr. Thomas Gillespie, University of Michigan, in his SAE-published textbook, "Fundamentals Of Vehicle Dynamics". YouTube interview follows below.)

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Detroit lost their collective way along the line. Well, just look at them now - they are paying for it.

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