Ways to Increase the Jeep JK Payload

[Metcalf]

I talked with AEV at easter jeep about the J8 chassis.

They said the only frame difference was the junction in the frame and a few additional brackets for the military 'lift' bumpers.

From what I gathered the JK frame is made of a front and rear frame section that is joined in the middle with a straight section of frame 'tube' material. The 4-door basically just has a longer 'tube' of material to make the overall wheelbase junction. The points at which those assemblies are welded together have a small bracket or brace over them on the civy version. On the J8 version that bracket is a LOT more heavy duty.

The leaf springs where used for an easy solution for more load capacity AND because the leaf springs work better for sway control with a trailer. The J8 is rated to tow 7000lbs vs the normal JK which is like 3500lbs.

 

[Piet]

Best way to increase available payload?
Cut stuff out... remove extra stuff. Don't add unessesary stuff.

You cannot increase the official payload capacity of a vehicle.

1. You can make it handle better under load.
2. You can carry more stuff than officially stated and not get caught.
3. But you cannot increase the official payload capacity of a vehicle.

Want to carry more stuff? Remove extra wieght!

• Do you really need a 400 lb bumper?
• 50 lb tires?
• Competition trail cage?
• 12 radios?
• A water heater?... (I think you know where I am going...)

When I was into protouring... you end up in the place where you are weighing all the bolts you are using to reduce wieght.
I think as offroaders, we could benefit from this thinking, rather than putting in a bigger engine. (says a guilty party)

 

[Metcalf]

In Canada do you get inspected on max weight of a vehicle?

I do tend to agree that most people carry too much stuff, but I do like my big tires

 

[Dan Grec]

Best way to increase available payload?
Cut stuff out... remove extra stuff. Don't add unessesary stuff.

I agree with your sentiment 100%. I drove Alaska to Argentina with little more than 1 small tool box, 1 small box of spares and a bag of clothes.

However, my next journey will be significantly further and through countries that have less in the way of spares available.
I'll be doing absolutely everything I can to minimize stuff, but I have no doubt I'll be bumping up against the weight limit of the JK. (if not going over)

-Dan

 

[Metcalf]

I would LOVE to get my hands on the factory test data and results from the testing program for the development for the J8.

They basically took a JK and subjected it to extreme off-road abuse and found out what failed....then the fixed the problems and gave it a huge increase in expected life, payload, and towing capacity.

The rough number I heard thrown around was that the J8 would last 3X as long as a stock JK over the same test standard....

Anyone have an in at JGMS?

 

[lbarcher]

In Canada do you get inspected on max weight of a vehicle?

I do tend to agree that most people carry too much stuff, but I do like my big tires

In Alberta? Seems to me that we're the last place you'd get an inspection on a non commercial vehicle.
I see everything from stoopid big lifted diesels to beaters that shouldn't be on the road every day.
Catalytic delete was a really common thing here as we have no emissions testing.

 

[Piet]

In Canada do you get inspected on max weight of a vehicle?

I do tend to agree that most people carry too much stuff, but I do like my big tires

When travelling inside Alberta in a non-comercial vehicle... you are mostly left alone.
When crossing provincial boarders with an RV... expect to get weighed... mostly because of Albertans with 4,000lb truck campers towing a boat trailer and then a quad trailer...

I love my big tires and big motors... Now I am trying the less is more route.

 

[jdzl]

In looking at the Jeep spec sheet - something isn't quite right. This looks like more of a ***-covering limitation than anything else, but I could be wrong.

2012 JKU Sport (MT)
- Curb: 4075
- GVWR (Standard): 5418
- GVWR (Maximum): 7942

So from curb to standard is: 1343 which I assume is:
... 22.5 gallons of gas * 6.5 lbs per gallon = 146.25 lbs
... 1200 lbs of passengers and misc fluids (Pretty much a worst case scenario... Even if fluids weigh 200lbs that's 5 x 200lb passengers... Cozy!)

Then from standard gvwr to max gvwr is: 2524
.... 1000 lbs is payload
.... What happens to the other 1524 lbs???

Also interesting to note is the Rubicon has a max gvwr of 8184 lbs, so presumably the engine, clutch, transmission, frame, etc are all good up to there - not to mention whatever safety margin Jeep puts on top of that which is probably not insignificant...

 

[Metcalf]

It is interesting that they list a 2nd GVWR.

The J8 3-door and 4-door according to JGMS is......

7416lb GVW
4850lb Curb Weight
2566lb Payload
7716lb Trailer towing

I think everyone needs to keep in mind that carrying around weight over paved roads just across town and down 500 miles of washboard track in baja are two COMPLETELY DIFFERENT THINGS. Just because the vehicle might be in some fuzzy zone about being able to carry some extra weight I would be VERY hesitant to load the vehicle heavily. The J8 program was developed for a reason. They tested the JK doing basically exactly what everyone on this board wants to do. They carried heavier loads in off-road conditions. They found the JK lacking in long term durability according to the testing and modified the platform to make the J8.

The big changes everyone knows about.....

Heavy duty frame gussets/plates where the front, rear, and center frame sections join.
Thicker wall tubing on the front axle.
D60 rear axle with larger tubes ( but still semi-floating and c-clip to boot!)
Bigger brakes on all four corners.
rear leaf springs instead of multi-link
Reinforcements on the front and rear bumper mounting to allow lifting the vehicle ( and stronger tow point? )
The body is suppose to be reinforced from the standard body ( I would love to document this? )

I would love to compile some concrete information on these differences and any others.

 

[Metcalf]

Another VERY good development case to look at would be the Earthroamer XVJP.

That was probably one of the most tested civilian heavy weight JK's

 

[Metcalf]

This was posted by Mhiscox over in the camper section.....good real world info from a longer term heavy JKU based vehicle.

Originally Posted by Metcalf
Hello, VERY cool project!
Thanks. It all turned out pretty trick.

I'm trying to collect some data on heavier payloads in JK Wranglers for another thread in the Jeep section....

http://www.expeditionportal.com/foru...eep-JK-Payload
I've been following that thread, as it is plainly relevant to my situation.

Do you have a total weight and front/rear distribution for your vehicle?
Figure 7000 pounds total. I don't have the distributions yet. I'll post up after I get to a scale.

Any modifications to the chassis for the added weight that you know of?
Yep . . . Big Goodyear Duratrac tires with more than enough capacity and a complete nth Degree/AEV suspension with the normal (3.5 inch) lift springs in the front and the heavy-duty (4.5) inch springs in the back.

Have you had any issues with your vehicle in regard to the higher weight?
Handling is excellent, and there's no drive on which I don't think well of Scott Brady for recommending this specific suspension. Also, for no reason I can think of, braking with the stock setup is quite good. I was expecting modifications would need to be made but I'm not having any problems.

The place the weight shows up is in vehicle performance. The shortcomings of the 3.8L V-6 are well-known and 7 kilopounds of curb weight doesn't help. But it is not a major crisis due to the 5.29 gearing, and I can readily get where I'm going at pretty much whatever speed I'm willing to pay for, since going fast takes more fuel. And the vehicle as I bought it already weighed that much so, with the improved suspension and tires, I'm actually a good deal better off now.

Plus the fact that my first overlander was an 8 ton Unimog camper with 125 horsepower has made all subsequent vehicles seem like a rally cars.

 

[jdzl]

So does that mean the JKU Max GVWR is actually the safety margin?

Applying that:

JKU Sport: Standard GVWR (5,418) vs Max GVWR (7,942) = 2524 (46% safety margin)
J8: Standard GVWR (7,408) + 46% Safety Margin = Max GVWR (10,815)

Not even sure that makes sense... Maybe?

 

[Metcalf]

The J8 is rated for a COMPLETELY different set of operating conditions. It's rated for its GVW and tow ratings basically on un-paved roads as far as I understand it.

 

[jdzl]

Wouldn't the above support that with it's theoretical Max GVWR being 10,815 and the JKU being 7,942?

That being said I would expect the JKU to be rated with offroading in mind too right? Granted, they're not doing 100k miles in a war-zone fully loaded, but still - I would expect that someone at Jeep hopefully spoke up and said "hey guys, make sure those numbers apply to dirt roads too"

Also interesting that they both share the same towing capacity of 3500lbs, but the J8 is rated to 7716lbs if towing a braked trailer.

I'd be curious to hear what Jeep has to say about these Max GVWR numbers - does that mean you can carry that and still have the 5/100k powertrain warranty apply? That's what I would expect since they're listing it on their site, but you never know...

 

[Metcalf]

I heard the stock JK lasted less than ONE circuit on the test course they used to develop the J8........when the J8 was done it would do something like 3+ circuits and then the testing was stopped. It was a big difference, much bigger than just dirt roads or not.

I do think that the wrangler was engineered to be used off-road more than most vehicles, but when you start to talk about max payload and/or towing I don't think the JK was developed to operate day in and day out on rough roads at close or over GVW.

I would probably look at the numbers like the max GVW was for pavement and the standard GVW is for dirt. That would probably be a far safer bet. I would still be VERY nervous about approaching some of those 'max' gvw numbers! That is a LOT of weight.