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  #1  
Old 06-18-2015, 11:11 PM
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Gross Vehicle Weight Rating & Rear Gross Axle Weight Rating

Hello

In August, we are travelling to outback Queensland including Birdsville and I have been investigating the weight of my Patriot SEL Outback caravan and MY2013 Jeep Grand Cherokee fully laden for the trip.

A couple of weeks ago, I packed my Jeep and Caravan as if I was heading off to Birdsville with additional water, fuel spare tyres etc and put both the Jeep and the Caravan over a Public Weighbridge.

Here are the figures:

JEEP GRAND CHEROKEE and SUNLAND PATRIOT SE-L CARAVAN
Actual Allowance
Kgs Kgs
Gross Combination Vehicle Mass (GCVM) 6240 6,449
Caravan Gross Trailer Mass (GTM) 3,020 3,324
Caravan Aggregate Trailer Mass (ATM) 3,340 3,500
Car Gross Vehicle Mass(GVM) 2,940 2,949
Tow ball weight 320 350

JEEP GRAND CHEROKEE From Handbook
Actual Allowance Variance
Gross Vehicle Weight Rating (GVWR) inc ball weight 3,260 2,949 311
Front - Gross Axle Weight Rating (Front GAWR) 1300 1,452 -152
Rear - Gross Axle Weight Rating (Rear GAWR) 1,960 1,678 282



Whilst initially both the car and caravan (independently) are under their respective ATM and GVM, it looks like there are issues with the Jeep GVWR and Rear GAWR.

I understand the tow ball weight needs to also be taken into consideration in the calculations of the Gross Vehicle Weight Rating (GVWR) – the Jeep GVM at 2940 + tow ball weight at 320 = 3260kg which is over the listed GVWR in the Jeep owner’s manual. I can drop the tow ball weight back to 280 by removing 40 litres of water stored in jerry cans on the front drawbar.

This puts the GVWR about 300kg over in total and the Rear Gross Axle Weight Rating (RGAWR) over by an amount of 282kg.

Have I calculated this correctly or have I misinterpreted the figures?

What are the options available?

I have looked at what I have in the Jeep to possibly reduce the payload of the Jeep but I cannot reduce it down by anywhere near 300kg – it just won’t work. I have a long range fuel tank that contains 75 litres of fuel, a cargo area including a 2nd battery and fridge, and I am carrying a second spare tyre for the jeep. All of these items I feel are necessary for where we are going.

Is there a way that strengthening the rear suspension and having it re-certified by say another 250-300kg would overcome the issue?

I would prefer not to use a weight distribution hitch due to my D035 off road hitch and some of the places I am travelling. I assume that using a WDH might move some of the weight on the rear axle to the front axle (let’s say 140kg) however the rear axle will still be some 150-170kg over.

Are there any other options that can be considered (apart from getting another vehicle which is not really an option)?

I look forward to your input and thanks for your assistance.

Cheers


Brian

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  #2  
Old 06-18-2015, 11:54 PM
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Re: Gross Vehicle Weight Rating & Rear Gross Axle Weight Rating

That's some load Brian, but credit for doing the hard work and assessing your pack properly.

One thing not mentioned is whether or not you have Quadralift... just regarding my "seat of the pants" commentary in which I have found my MY14 (with QL) quite underdampened with only 260Kg on the ball, and just a 55L fridge in the boot. How did yours feel heading to the weighbridge? Was it porpoising?

I expect you are aware that Jeep "recommend" a WDH with loads over ~2200Kg. Just saying... not bashing you over the head with it. I try to avoid using one too

I am working off this being your van with all standard features listed: Patriot SE-L - Sunland Caravans

My thoughts are:
- Move second car spare wheel to under van, preferably over axles, otherwise as near as water storage permits. To hang it, get a "spare wheel winch" from the wreckers or eBay.
- Remove second battery from car and move to storage in van, preferably over axles. Rewire to use van power when connected and install second battery to car when not. Or better still delete the second car battery and borrow a Lithium out of the van when required.
- Move any particularly heavy relocatable items in drawbar box or in forward storage areas to over axles. Avoid shifting weight to the rear bar due to the effect on stability.
- Cull some stuff.
- Consider repowering car with Lithium batteries.
- Use WDH and remove when required.

Good luck!
Steve
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Old 06-19-2015, 12:41 AM
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Re: Gross Vehicle Weight Rating & Rear Gross Axle Weight Rating

Oh, and this is where most of the Aussie discussion takes place ;-)


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Cheers,
Steve
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Old 06-19-2015, 01:08 AM
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Re: Gross Vehicle Weight Rating & Rear Gross Axle Weight Rating

Thanks Steve.
It is a Patriot SEL with upgrade to 3500kg with 2nd spare wheel, and gas heater included.
No I do not have Quadralift on my jeep. I have raised the suspension all round by approx 2inches by Murchison After Market, and I do have Heavy duty Airbagman airbags on the rear of the jeep which I pump up to 30psi - they can go higher. The jeep and the caravan both sit level when towing and there is little if any porpoising. I have used WDH previously but had to replace my DO35 hitch as it was damaged by getting caught on the WDH, so I stopped using the WDH without any ill effect.
I can relocate some of the stuff but suspect I would still be over.
THanks for your input
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Old 06-19-2015, 01:32 AM
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Re: Gross Vehicle Weight Rating & Rear Gross Axle Weight Rating

I use a DO35 in conjunction with an older welded ball-mount Classic (straight trunnion bar) HR WDH, as no adaptor is required... therefore no extra overhang length. This is important, especially in your situation. Unfortunately none of the current Aussie HR products work without the DO35 extension adaptor, as you have found out. The Reece USA system sold by Camec could also work, but it has the curved bars, which hang down a bit too far with bottom mounted trailer couplings.

FWIW, if an engineer were to plate your car GVM up, I believe you're still pushing the physics of the current pack a bit too far. Some people stay lucky... some people come to grief.

Cheers,
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Old 06-19-2015, 01:34 AM
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Re: Gross Vehicle Weight Rating & Rear Gross Axle Weight Rating

Oh... here's another:

- Remove rear seats if not used.
- Move fridge to rear seat area.
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Old 06-19-2015, 02:39 AM
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Re: Gross Vehicle Weight Rating & Rear Gross Axle Weight Rating

Thanks again.
I will investigate all the avenues. I used to have the fridge on the rear seat and installed an Outback Solutions cargo bay option.

The WDH I previously used was an Ezy Lift with straight bars. I will see if the HR extension plate done by Motor Vehicle Components who make the DO35 hitch and the extension plate can be adapted to the Ezy lift WDH.
Again thanks for your advice
Cheers
Brian
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