Truck camper payload question?

[Rrliljedahl]

I have a truck camper payload question. If this is the wrong forum, I apologize in advance. I also posted this in the truck forum.

We recently put a deposit down on a flatbed Northstar Escape Pod 900 SD truck camper (9ft x 7 ft) with an estimated dry weight including options to be 2300 pounds.

Additional wet weight will include water (40x8.3=332 lbs), people (275 lbs), LP tanks (2x25=50 lbs), batteries (2x55=110 lbs), plus any food and gear easily adds up to 1200 pounds.

I estimate my payload to be at least 3500 pounds.

My thoughts on truck selection include:
Cab creature comforts so that wife is happy
pre 2007 federal diesel pollution requirements making travel to Mexico easier.
Single rear wheel and 4x4 as we want the ability to go off road.

I found a 2007 Classic GMC 3500 LBZ diesel crew cab 4x4 (I will have to install a flatbed).
70000 miles.
SLT trim level
LBZ Duramax 6.6/Allison 6 speed transmission
Heavy duty trailering package
heavy duty locking rear differential
Transmission cooler
3.73 rear axle ratio
GVWR of of 9900 pounds
GAWR RR 6500 pounds
GAWR FF 4800 pounds
Tires are Michellin P265/75R16 LTX E2 (3400 pounds at 80 PSI).

The dealer says that there is no sticker on the door as to payload capacity of this vehicle but there is a sticker in the glove box stating camper should not exceed 2200 pounds. In cruising the Internet, some suggest that the payload as specified by GMC might be as low as 2800 pounds.

I will have to travel 500 miles to see this vehicle.
Before doing so, I hope to get a couple of questions answered here:
Does anyone know how to find the payload capacity for this vehicle?
If the payload is truly only 2800 pounds, is this truck from a practical standpoint capable of handling this camper? If so, what modifications will need to be made?

I do not want to have a discussion of merits of Ford Versus GM versus Dodge.

Thank you in advance.

[bjbear]

wnjj wrote:

bjbear wrote:
The GVWR is important, be because there are so many factors included in this rating, I believe there is some wriggle room. Nobody as far as I am aware regulates being over this rating (i.e. you won't get a ticket). However, just be aware, that if you are climbing a steep hill, at high altitude on a very hot day, you might have problems. Also, you have to think of the brakes going down hill as well.

I agree with the wiggle room thought. As for pulling a steep hill in the heat, towing at GCWR requires far more power than hauling a camper that puts you over GVWR. The engine doesn't care if it's onboard or being towed. Brakes are probably the real limit beyond suspension but consider it like a being at GVWR and towing a small trailer without brakes on it and drive accordingly.

The steep hill was just an example..... What I was trying to express is that when they set the GVWR, they run many different scenarios and design for the almost worst case. It is a trade off between providing a vehicle that will meet most peoples needs and the high cost to design the truck for ALL possible scenarios. In other words, if you are over GVWR, you will have no problems on the flat on a moderately cool day. However, at some point you may exceed the "almost worse case" and you might have problems.

[wnjj]

bjbear wrote:
The GVWR is important, be because there are so many factors included in this rating, I believe there is some wriggle room. Nobody as far as I am aware regulates being over this rating (i.e. you won't get a ticket). However, just be aware, that if you are climbing a steep hill, at high altitude on a very hot day, you might have problems. Also, you have to think of the brakes going down hill as well.

I agree with the wiggle room thought. As for pulling a steep hill in the heat, towing at GCWR requires far more power than hauling a camper that puts you over GVWR. The engine doesn't care if it's onboard or being towed. Brakes are probably the real limit beyond suspension but consider it like a being at GVWR and towing a small trailer without brakes on it and drive accordingly.

[bjbear]

Rrliljedahl wrote:
I bought the truck and took it to a scale.
2007 Classic Sierra 3500 Crew Cab, Long Bed, LBZ Duramax and Allison Transmission, 4X4, SRW

GVWR of of 9900 pounds
GAWR 6500 pounds
GAWR 4800 pounds
Michellin P265/75R16 LTX E2 (3400 pounds at 80 PSI).


With a 1/4 tank of gas and no one in the cab
the truck weighs 7060 pounds
front axle weight 4160
rear axle weight 2900

It would appear that leaving everything stock
My rear tires will let me carry a payload of (2x3400=6800-2900=) 3900 lbs putting my gross vehicle weight at 10960 which is over the stated GVWR of 9900 lbs.

Rear axle weight restriction as specified by GM would let me carry a payload of (6500-2900=) 3600 lbs. putting my gross vehicle weight at 10660 lbs which is over the stated GVWR of 9900 lbs.

Others have stated that the 11.5 AAM axle on this vehicle is the same as on a dually from that year and that the dually axle can take 9375 pounds which I am assuming has to do with the 2 extra tires in the rear. Redoing the calculations giving me a payload of (9375-2900=) 6475 lbs putting my gross vehicle weight at 14075 lbs which is way over the stated GVWR of 9900 lbs. I realize that I can not approach this even if I upgrade the tires and suspension.


What am I not understanding here?

Rrliljedahl I ran the numbers you gave though my calculator. If I got everything correct, it suggests you will be over your GVWR a little, but OK on Axles & Tires. In my opinion, you are OK with this rig as I am in the camp that going over GVWR is a manageable risk.

http://www.visualsc.com/Rrliljedahl_1.pdf

You can re-run the numbers yourself and play with them to add additional weight to see where you end up. http://www.visualsc.com/tc_calc.htm

There is always lots of confusion about how the rating numbers apply. It is really simple though. Each rating is taken individually and you compare the actual measurement to the rating. No need to calculate any combinations.

Tire and Axle weights are the most important and are legislated in many places. From a safety standpoint, I do not recommend exceeding these (just my opinion before someone jumps on me about supplier ratings vs. GMC/Chev ratings!!)

The GVWR is important, be because there are so many factors included in this rating, I believe there is some wriggle room. Nobody as far as I am aware regulates being over this rating (i.e. you won't get a ticket). However, just be aware, that if you are climbing a steep hill, at high altitude on a very hot day, you might have problems. Also, you have to think of the brakes going down hill as well.

[Rrliljedahl]

I bought the truck and took it to a scale.
2007 Classic Sierra 3500 Crew Cab, Long Bed, LBZ Duramax and Allison Transmission, 4X4, SRW

GVWR of of 9900 pounds
GAWR 6500 pounds
GAWR 4800 pounds
Michellin P265/75R16 LTX E2 (3400 pounds at 80 PSI).


With a 1/4 tank of fuel and no one in the cab
the truck weighs 7060 pounds
front axle weight 4160
rear axle weight 2900

It would appear that leaving everything stock
My rear tires will let me carry a payload of (2x3400=6800-2900=) 3900 lbs putting my gross vehicle weight at 10960 which is over the stated GVWR of 9900 lbs.

Rear axle weight restriction as specified by GM would let me carry a payload of (6500-2900=) 3600 lbs. putting my gross vehicle weight at 10660 lbs which is over the stated GVWR of 9900 lbs.

Others have stated that the 11.5 AAM axle on this vehicle is the same as on a dually from that year and that the dually axle can take 9375 pounds which I am assuming has to do with the 2 extra tires in the rear. Redoing the calculations giving me a payload of (9375-2900=) 6475 lbs putting my gross vehicle weight at 14075 lbs which is way over the stated GVWR of 9900 lbs. I realize that I can not approach this even if I upgrade the tires and suspension.


What am I not understanding here?

[btggraphix]

DiploStrat, I bet our recently returned and sorely missed resident axle expert (SoCalDesertRider) will comment at some point again. But if I had to guess, when RedSky said "axles" he might have meant the combined GAWR of the two axles. That would perhaps be about right. My old gimmy was 6086 rear and maybe 4K+ front. And I think those ALCOAS I bought were either 3400 or 3600 rated. Can't help you with suggestions though....I have 6 19.5's with a total tire capacity of nearly 27,000 pounds!

[DiploStrat]

Redsky wrote:

...
The axles are rated at 10,900 lbs. so the weak links are the springs and the tires. Easy to add helper springs and there are tires like the Toyo and Nitto Terra Grappler that support up to 3750 lbs. with the stock rims.

Do you have a good source for that number? (I hope you are right!) As I read the on line specs for my 2013 Chevrolet 3500 I am seeing a number on the order of 7,000 libs and I am looking at exactly the same problem. (Ironically, I even looked at the Northstar at one time.)

The Nitto Terra and Trail Grappler, in LT295/70x18E come out at over 4,000 lb.. each. (You will need gentle lift and trimming.) The challenge seems to be to find wheels rated at over 4,000 lb.. All of the aftermarket stuff that I can find is rated at 3600 lb.

Anyone have good ideas other than Rickson 19.5?

[btggraphix]

Redsky wrote:
...

The axles are rated at 10,900 lbs. so the weak links are the springs and the tires. Easy to add helper springs and there are tires like the Toyo and Nitto Terra Grappler that support up to 3750 lbs. with the stock rims.
.....

Better check on the rims though, my old GMC rims (granted it was a 97) were only rated for 3043 or "maybe" 3400 but not more than that. When I went to the higher capacity tires I also bought some ALCOA rims that were rated higher....enough to match the tires I put on.

[Redsky]

The 2006 to early 2007 "Classic" trucks with the LBZ are very reliable so long as you keep the fuel clean. Traveling in Mexico I would want to use a two stage filtration setup and lots of info on the Duramax forums on how to do this. Not all that expensive either to do.

The axles are rated at 10,900 lbs. so the weak links are the springs and the tires. Easy to add helper springs and there are tires like the Toyo and Nitto Terra Grappler that support up to 3750 lbs. with the stock rims.

Have the truck checked at a shop that does front end repairs. These trucks are supposed to have the 11 lube points greased every 3,000 miles and this is seldom done. A bad tie-rod or ball joint could be very dangerous even with the truck empty. Not that expensive to have these parts replaced.

I would avoid a truck that has been chipped as the transmission is going to be stressed and that can entail a $3-4K repair bill.

[Rrliljedahl]

wnjj wrote:

Rrliljedahl wrote:
I estimate that the crew cab long bed 4x4 diesel truck weighs 7100 pounds without the camper but I do not know how much of the weight is being carried by the rear axle.

Where do you go to figure that out?

Once I know that number I could estimate the rear axle weight with the camper.

If it helps your estimates any, I have a 2005 3500 SRW 8.1L ext cab 4x4 that weighs 4000 on the front and 2950 on the rear without the camper on. The diesel will only add to the front and the crew cab will probably add a little to both ends. I think this was with a 200# driver in the cab.

WNJJ
That helps me quite a bit as I have been trying to figure out the axle weights as the vehicle comes from the factory.

Thank you.

[wnjj]

Rrliljedahl wrote:
I estimate that the crew cab long bed 4x4 diesel truck weighs 7100 pounds without the camper but I do not know how much of the weight is being carried by the rear axle.

Where do you go to figure that out?

Once I know that number I could estimate the rear axle weight with the camper.

If it helps your estimates any, I have a 2005 3500 SRW 8.1L ext cab 4x4 that weighs 4000 on the front and 2950 on the rear without the camper on. The diesel will only add to the front and the crew cab will probably add a little to both ends. I think this was with a 200# driver in the cab. You can probably assume about 3000 on the rear when empty with the tailgate on.

[btggraphix]

PS: Another thing you might want to consider, is going to a local dealer, or finding someone selling a very similar truck. Check it out and test drive it to a truck stop and get it weighed, empty. Just make sure it is a diesel crew cab. That weight will help you guestimate the weight of the one you are considering. Harder to find a perfect match for an older truck like that to test weigh....but I do bet that someone on the forum has something nearly identical that knows their empty weight.

Just keep in mind the weight of a flatbed if you convert. Even with aluminum, you might gain 500 pounds of weight depending. Well over that for steel I would guess. I did seriously consider putting a wooden flatbed on my old 2500 because I desperately wanted a flatbed, but had zero extra capacity (negative really) on that truck with that camper. But even a wooden bed would have been heavier (substantially) that the "pretty" sheet metal bed it came with and we knew we wanted a bigger camper someday in the future. 6 years, 75K miles and well over 400 nights in our new truck/camper (us alone, not counting the 32K miles and 11 months in C/S America and we couldn't be more pleased with it.)

[btggraphix]

Sure, you can go over the GVWR (though most everyone agrees not to go over axle limits.) My old rig was well over GVWR, and I band-aided it a lot and it worked pretty well. It was a 2850# camper, which weighed about 3500 with all gear and fluids, but my truck was a gas engine, extended cab 2500, so my payload was technically about 2500 and I was over by 1000 pounds. It drove fine on the highway and felt pretty safe overall with my improvements (learned over 7 years of using that combo. Being that overweight, and top-heavy to boot, is really not the way I would want to travel to Central and/or South America, or even into the way way remote places in the USA and certainly NOT the way I want to be setup when hitting that pothole in the middle of the highway in Mexico and having a blowout. Tippy forest service roads are no fun either, in an overloaded top-heavy vehicle.

There is no issue putting on dually swing-out brackets on the Northstar to make them wide enough to clear a flatbed, even of standard width. You'd want very good beefy ones to extend that far of course. But of course, you'd be wasting 1' of bed width in terms of space.

I would certainly consider a dually if heading off southward and were concerned about weight, safety, and preparedness for anything.

As an example, the people that put my rig together bought the Kodiak 4500 from a lot with a flatbed already on it. Did some chopping on the bed to allow it to sit all the way forward, bought a Lance 1191 camper off the lot, dropped it on the flatbed, and spent their first night in the Lance, on their way from Connecticut to Argentina (shipping by boat from Panama to Peru, and on the way back from Buenos Aires to Panama.) They took a plug kit and no spare tires. had no truck or camper issue to speak of during their 11 month trip.

The more capable of handling heavy weights, the better likelihood of having no issues with your truck.

I'm just posting this for your consideration of your options. Food for thought if you will. It sounds like this might be a dream trip for you, and I hope it goes really well either way. No reason you can't setup without going to a dually, and truth-be-told no reason you couldn't put a 7' wide flatbed on it, but another consideration, unless you go with a really high-end aluminum flatbed (probably the "best" route) you will also be adding significant weight to your truck over the flimsy sheet metal bed that it comes with. Going that route I picture the bed on one of those Home Depot rental trucks with your little Northstar and it could be a sweet setup, no doubt. But in terms of the truck itself I'd be seeing an extended cab (not crew) and a gas engine to maximize your weight capacities.

Good luck.

[12V_Cummins]

Ranger Smith wrote:
Well if you are estimating the camper to be 3500 lbs and tires rated for 3400 lbs there is a problem right there???

At least I think there is.

I hope not all the weight is on one tire.

[SoCalDesertRid1]

Almost ALL of the camper's loaded wet weight is carried by the truck's rear axle. Most bigger campers have their center of gravity located not very far ahead of the truck's rear axle. Then most of the storage areas are toward the rear of the camper, so weight of gear loaded in camper ends up behind the truck's axle. This moves the actual, fully loaded center of gravity position further to the rear, than stated by the camper manufacturer.

So, assume that all of the campers loaded weight is carried by the rear axle and add that loaded camper weight number to whatever the empty truck's rear axle weighs (minimum 3000 lbs), and that is the minimum the truck's loaded rear axle will weigh.

If you pull a trailer, the trailer's tongue weight is also carried by the truck's rear axle.

Also, realize that weight of people and gear in the cab of the truck is carried partially by the rear axle and partially by the front axle, since the cab is positioned between both axles.