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Unread 04-25-2012, 03:11 PM   #1
reelnole
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new jeep unlimited

I am thinking about buying a new wrangler unlimited with the pentastar engine. However I tow a 4500 pound boat. I have a liberty now and it tows fine. If the unlimited has more power and a longer wheelbase than my liberty why is the tow rating only 3500 pounds. Nobody at the dealership can tell me.

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Unread 04-25-2012, 05:14 PM   #2
WXman
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Well, I'll tell you why. It's because if Jeep rated the Wrangler for what it's actually capable of towing, it would be poor business. Each model in the Jeep lineup has to have unique selling points. If the Wrangler and the Grand Cherokee had the same tow ratings and the same physical size, it would hurt sales. As it is, they can market the Wrangler as the offroad model, the GC as the luxury and heavy towing model, and the Liberty as the compact and capable model.

Truth is, the Wrangler mechanically is the best towing vehicle in the entire Jeep lineup. Ladder frame, solid axles, Pentastar engine, deeper gearing options, etc... it should have the highest towing capacity available in a Jeep but you'll never see them label it as such.
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Unread 04-25-2012, 06:32 PM   #3
awinski
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good answer
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Unread 04-25-2012, 07:22 PM   #4
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Quote:
Originally Posted by WXman View Post
Well, I'll tell you why. It's because if Jeep rated the Wrangler for what it's actually capable of towing, it would be poor business. Each model in the Jeep lineup has to have unique selling points. If the Wrangler and the Grand Cherokee had the same tow ratings and the same physical size, it would hurt sales. As it is, they can market the Wrangler as the offroad model, the GC as the luxury and heavy towing model, and the Liberty as the compact and capable model.

Truth is, the Wrangler mechanically is the best towing vehicle in the entire Jeep lineup. Ladder frame, solid axles, Pentastar engine, deeper gearing options, etc... it should have the highest towing capacity available in a Jeep but you'll never see them label it as such.
Quote:
Originally Posted by awinski View Post
good answer
Bad answer and probably the stupidest thing I have ever heard. Why kill sales of one line when having TWO lines would DOUBLE sales as BOTH lines see equal interest and pull from other brands? That would be like McDonalds killing all but one hamburger, one cheeseburger, one chicken sandwich and one fish sandwich. Ford has been kicking everyones rear in Truck sales (not just bragging - the F series has sold more units than anyone else throughout history) simply because every member of the F and E family has a HIGHER rating than the average counterpart in the competing brands.

The SAE's Surface Vehicle Recommended Practice J2807 spells out in precise terms a procedure for determining two important ratings: the maximum permissible gross combination weight (GCWR) for a tow vehicle and its trailer and the maximum permissible trailer weight rating (TWR).

There are five engineering characteristics that strongly influence any tow vehicle's performance and rating under SAE J2807:
The engine's power and torque characteristics.
The powertrain's cooling capacity.
The durability of the powertrain and chassis.
Handling characteristics during cornering and braking maneuvers. (direct result of suspension design).
The structural characteristics of the vehicle's hitch attachment area.

SAE J2807 spells it out nicely. Probably the biggest thing holding the wrangler back is the dual 4 link, opposing track bar, live axle design. Although best for crawling rocks the low roll center (ground level) coupled with the high center of gravity (about 26" above ground front axle line and 18 above rear axle line) makes a HUGE roll moment - and a momentum line that is sharply lower in the rear!. This would make a heavier trailer way more likely to tumble that tow rig when hard on brakes and hard in an evasive maneuver. The Grand has non parallel control arms (roll center probably about 5" above ground) and lower CG (about 20" above ground) thus a shorter roll moment AT BOTH ENDS and the liberty is just below that (even a pickup with 4 link live rear and cntrl arm front has a MUCH lower roll moment line - although leafs (roll center about even with axle line) rear and ctrl front - (especially Fords twin I Beams with a roll center that moves upward with added weight) is ideally the best as then the moment line angles down in the front!).

To simplify - roll center is the mechanical axis upon which body roll occurs and is dictated by suspension design and geometry - center of gravity is the application to the lever created by the distance between the two points (the moment). The longer the distance - the longer the leverage (moment) the more the vehicle wants (roll momentum) to body roll (lean) in cornering. (the roll moment front combined with roll moment rear creates the roll moment line) The higher the roll moment line the lower the towing capacity per SAE (all things else being equal) - PERIOD. Roll is noticed as when you turn right the car leans left - the weight passing over the roll center! (if an indy car could tow it would be awesome - their centerline of gravity is below the roll center - so rather than the weight passing OVER the roll center and the car rolling opposite the steer - it passes UNDER so the car rolls INTO steer - banks left when turning left and banks right when turning right - but with weight and suspension travel that design would get very scary once you are seeing more than just the fraction of an inch negative roll momentum they see)

Sales, marketing and brand or model favoritism are nowhere in SAE J2807 - the engineering standard that sets what rating is given any vehicle - it is simple math and calculations followed by testing at the proving ground!
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Unread 04-25-2012, 07:46 PM   #5
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Quote:
Originally Posted by jwmbishop
Smack down of the year
I want to see an F1 car towing something. Anyone got the connections to make that happen?
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Unread 04-25-2012, 08:31 PM   #6
awinski
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i was simply agreeing that the solid axels stronger motor and gearing would seem to give it a better tow rating. truth is some one has to test it out before anyone can give a true answer. anyone got 30k to waste on this experiment?
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Unread 04-25-2012, 08:39 PM   #7
WXman
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My answer was not only a good answer, it was the TRUE answer.

Now you can go bury your nose back in your engineering book.

Why do you think Ford really killed the Ranger? Why did Jeep kill the Commander? There is this concept known as "canabalizing your brand". You cannot have multiple vehicles in your lineup that do the same things. It leads to poor sales.

This is why my father always told me there is a difference between "book sense" and "common sense". Unfortunately I have to work with engineers every day of my life.
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Unread 04-25-2012, 09:05 PM   #8
73azbronco
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I think both fo you are right, Jeep decides NOT to comply with segments of that standard SO they can manage their inventory and stop competing against itself. Why sell one JK which can tow 10,000lbs when you can sell that owner a JK AND a Dodge Ram?
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Unread 04-26-2012, 01:16 AM   #9
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WXman .....your answer may be right or not. I truly don't know. I will make one observation you seem to have a chip on your shoulder that you know everything and are the complete authority on Jeeps.

You repeatedly jumped on my posts about the wheels that were on Jeep, from Jeep at delivery, telling me that I was wrong and when I gave you the part number and size from the build sheet your final response was "Hmm.. that's odd. Did you get a special order set of wheels or something"

I originally was accepting you as a knowledgeable guy, and looking to you for valuable input regarding tires that I could fit on my jeep, but it seems more and more like you just want to an obnoxious online know it all .... like your comment above "Now you can go bury your nose back in your engineering book"

If you are really that talented and knowledgeable it will shine thru without snide remarks. If you constantly are announcing that you are right and others are odd or should go stick their head in a book ...i'm certain I will not be the only person ignoring your posts.

I am here a little bit for the friendship ( at my age I have all the friends I really need ) but I am here mostly for the knowledge that is available here. There is no need for me to reinvent the wheel when so many people, probably including you, have done or know how to do whatever I want to do with my new jeep. so in 2 words ...lighten up !
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Unread 04-26-2012, 01:21 AM   #10
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Quote:
Originally Posted by djm
so in 2 words ...lighten up !
I would've chosen two different words, but I wholeheartedly agree with what djm has expressed.
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Unread 04-26-2012, 06:35 AM   #11
WXman
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Look, it's like this... Chrysler's undisputed champ in the towing department is the Ram 2500/3500. Guess which Jeep is most similar to the Ram? You guessed it...the Wrangler. The solid axles, the gearing ratios, the design of the multi-link suspension, etc.. the Wrangler underpinnings look like a miniature version of the Ram pickups. In fact, the Ram got it's suspension design from Jeep to begin with.

You can try to rationalize it with SAE garbage all day long, but the facts are the facts. By the way.. Toyota is the ONLY company currently using the SAE towing standards to rate it's trucks. So throwing the guidelines out there is a moot point on a Jeep forum.

So, to review class.. what we've learned today is that the Jeep Wrangler Unlimited should have the highest towing capacity in the entire Jeep lineup. BUT.. it doesn't, because it would be a poor business case to have a Wrangler that can do EVERYTHING and a Grand Cherokee and Liberty that can only do certain parts of everything.

It's unfortunate, because if you put your 4,500 lb. boat behind a JK it'll tow like a dream but will violate laws and regulations.

The end.
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Unread 04-26-2012, 06:57 AM   #12
LIJeepJC
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Quote:
Originally Posted by WXman
Well, I'll tell you why. It's because if Jeep rated the Wrangler for what it's actually capable of towing, it would be poor business. Each model in the Jeep lineup has to have unique selling points. If the Wrangler and the Grand Cherokee had the same tow ratings and the same physical size, it would hurt sales. As it is, they can market the Wrangler as the offroad model, the GC as the luxury and heavy towing model, and the Liberty as the compact and capable model.

Truth is, the Wrangler mechanically is the best towing vehicle in the entire Jeep lineup. Ladder frame, solid axles, Pentastar engine, deeper gearing options, etc... it should have the highest towing capacity available in a Jeep but you'll never see them label it as such.
This really doesn't hold water considering the G C and the JK are two different vehicles that attract two VERY different buyers for the most part. So I think that to limit selling points is stupid. But hey, what do I know??
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Unread 04-26-2012, 06:59 AM   #13
LIJeepJC
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Quote:
Originally Posted by WXman
My answer was not only a good answer, it was the TRUE answer.

Now you can go bury your nose back in your engineering book.

Why do you think Ford really killed the Ranger? Why did Jeep kill the Commander? There is this concept known as "canabalizing your brand". You cannot have multiple vehicles in your lineup that do the same things. It leads to poor sales.

This is why my father always told me there is a difference between "book sense" and "common sense". Unfortunately I have to work with engineers every day of my life.
Maybe because they weren't selling?
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Unread 04-26-2012, 07:04 AM   #14
paul84043
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Sorry reelnole, class isn't usually this rowdy.... They've been cooped up all winter...

I don't think I would personally try to tow a 4500 pound boat with the wrangler.
Without going into an engineering dissertation, common sense dictates that if you were to get into a tight spot and the trailer were to begin to wag the dog, I have a feeling that a 4500 pound tail would probably roll that dog over pretty fast.
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Unread 04-26-2012, 07:37 AM   #15
xkuzme1
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The European JKU with the same axels, engine, tranny, wheelbase, weight, can tow 7000. Europe has worse lawyers.
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