Let's Work Backwards

skychief12 · 06-12-2021, 10:54 AM

Using my 1/2 ton truck. I find it's GVWR is 6800. The max cargo (payload) is 1543. The owners manual shows Gross Combination Weight is 15,000.
Assume the only additional Weight is 350 for driver & passenger.

Taking GCVR 15,000 - GVWR 6800 = 8200. Passengers 350 - 8200 = maximum trailer Weight of 7850.

Assuming 10% hitch weight = 785. 785 + passengers 350 + 785 = 1135. Payload 1543 - 1135 = Maximum allowed additional cargo of 408.

I should add max trail 7850 - 1000 cargo = 6850 max trailer weight.

Have I got this correct?

**chuckster57** · 06-12-2021, 11:40 AM

Youneed to subtract the weight of the hitch from your payload. Figure about 100 pounds. Other than that I think you got it right.

skychief12 · 06-12-2021, 11:56 AM

Thanks I missed it. How does a weight distribution hitch effect the calculation?

jsb5717 · 06-12-2021, 12:01 PM

It's additional payload that the truck has to carry.

**chuckster57** · 06-12-2021, 12:23 PM

Quote:

Originally Posted by skychief12

Thanks I missed it. How does a weight distribution hitch effect the calculation?

It will transfer some of the tongue weight to the front axle IF its set up properly.

**sourdough** · 06-12-2021, 01:01 PM

Your last comment about "1000lbs. cargo" and subtracting it from the trailer weight, what is that? If looking at tongue weight for a 7850 trailer estimate 1020 lbs. or 13%. Use the same percentage for 6850 - I assume those are loaded trailer weights.

Using your numbers for the truck and the other numbers you backed in;

Payload- 1543
Passengers- (350)
Hitch- (120)
Tongue- (1020)
Excess payload 53

The problem with those numbers as I see it is the other things required to go camping. There WILL be more in the truck than just the passengers and hitch. It is always a mistake to try to figure the very least possible to get by to allow a bigger trailer, then find that those bare bones numbers bear no semblance to reality.

Maybe that's what the 1000lbs. is for?

skychief12 · 06-12-2021, 01:33 PM

The 1000 is cargo added to the trailer. So yes its loaded trailer.

**sourdough** · 06-12-2021, 03:02 PM

Thanks. So let's look at it more forward;

You have an Atlas 2732RB; gvw 9680; length 31 1/2; dry 6828; carrying capacity 2852. You have your 1/2 ton pickup; gvw 6800; payload 1543.

When backing into it using reduced numbers the 1/2 ton was going to be overloaded (in reality). So using these numbers - 9680gvw x 13% = 1258lbs. for tongue weight. 350lbs. for passengers; 120 for hitch = 1728lbs. used in payload vs 1543.

Now, you will have more in the truck than passengers and hitch, that is a given. On the other hand I would be shocked if you were able to use up that 2852 carrying capacity of the trailer. If you are actually going to take off and hit the road in retirement 1000lbs. won't be enough either (I carried 12-1300lbs. in my 10k gvw bumper pull). But, that is where your bed will be used; to carry those things you don't want in the pass through, want easy access to etc. And remember, of that 1000lbs. you estimated for cargo over 100lbs. of it disappeared with propane and batteries.

Without scale weights the best, easiest and safest thing to do is use the gvw of the trailer. Other possibilities are endless and tend to lead folks to do what I think you are trying to do; estimate on the low end to make the truck "work" with that trailer - happens every day. That is too much trailer for the truck if loaded like you will want to use it....and take the things you want to enjoy.

I pulled my similar sized bumper pull with a 1/2 ton; NO fun. Constantly leaving piles of stuff at home trying to conserve weight; braking was enough to put permanent creases in the drivers seat of the truck and wind/buffeting was a constant. That was with air bags and LT tires.

I'm not trying to be a downer. You just retired and got this trailer, I want you to be safe and have a great time...because RVing IS a great time. Don't want it to be a "chore" you dread, or worse yet, fear. IMO the realm of a 1/2 ton truck towing runs out at about 7500lbs. - and I've owned a lot of them.

LHaven · 06-12-2021, 05:59 PM

When I work this backward, I get:

(1543 payload - 350 people - 100 hitch) / .13 hitch weight = 8,400 max trailer weight.

But that exceeds (GCW-GVWR = 8,200), so take the smaller number: 8,200.

That's a 1,066 tongue load, plus 350 + 100 makes 1,516 payload, which is on the hairy edge (about a pet's weight).

i guess that can't be too wrong, since the slack is real close to sourdough's final slack.

**JRTJH** · 06-12-2021, 06:38 PM

Being on the edge like this is NO FUN !!!!!

Let's look at any number of the "hundreds of threads" where members have done this, decided that they needed LT tires with stiff sidewalls to help combat sway, they needed air bags to level the truck and help prevent the rear from being too low. They needed floor mats or a tonneau cover or a shell on the truck to protect it. They wanted to add a TPMS to monitor trailer tires, needed a GPS to help with navigation, wanted "just a little cooler in the truck for a couple bottles of water, "DW's purse, some maps, the phones and a jacket, an umbrella and well, that tool box in the bed, oh and DW refuses to let me put the grill in the passthrough after things got greasy last time, so I now put the grill in the truck bed..... And I forgot about the firewood and the generator that won't fit in the passthrough and the 5 gallon gas can for the generator and the ...... (fill in the blanks)....

If you're "running on the jagged edge, how are you going to make any of the above additions?????

NEVER (did I mention N E V E R) calculate "to the jagged edge"... If you do, and don't have time for your "morning constitutional" well, you get the "crappy idea that you'll be overweight"... Now, don't consider stopping at McD's and getting a Big Mac to go....

NEVER calculate "to the jagged edge".....

jsb5717 · 06-13-2021, 06:58 AM

Quote:

Originally Posted by JRTJH

NEVER calculate "to the jagged edge".....

Especially on a 1/2 ton truck. There is a fairly significant difference between a 1/2 ton and a 3/4 or 1 ton in terms of general stability. Being at or slightly over payload on a 1/2 ton feels different than being at or slightly over on a 3/4 ton. Also, and perhaps equally serious is the white-knuckle experience of pulling a trailer approaching 30' or more. Even if you manage to stay within parameter of the 1/2 ton payload you will still enjoy the drive much less as the wind or passing semi's push your trailer around so the tail is wagging the dog. Personally I wouldn't want to haul a tall sided trailer longer than about 25' with a 1/2 ton. YMMV

Ken / Claudia · 06-13-2021, 07:16 AM

The feds made matching a RV to a TV pretty darn simple nearly 20 years ago. When they required the payload of the TV and before that the GVWR, axle GVWR all must be displayed, (right?) No need to reinvent the wheel, as we used to say at work to get the job done.
I understand new folks may have a hard time figuring what those numbers mean, but there still the same numbers if you look forward or backward.
Members on here have an easy time explaining the details, but how one can take an X for example and call it a Y. New math I guess.

**flybouy** · 06-13-2021, 07:24 AM

I love math. It's science in its purest form and it's used to prove nearly every scientific theorem. Why? Because it doesn't lie. And while you can use different formulas if the numbers don't change neither do the results . 4+4=8 and 8-4=4, you can slice it and dice it but you'll never get a different correct answer.

Laredo Tugger · 06-13-2021, 07:46 AM

True Marshall, but I only need the number 4 for short trips without everything I need and not fully loaded. I'll be OK............

RMc

skychief12 · 06-13-2021, 08:00 AM

Agree with Flybouy.

I'm not seeing that calculations are wrong. I did assume best case rather than worse case. Bottom line is either way loading weights need to be monitored as well as CG.
I'm not sure I'm going to hit 30 degree hills in Texas.

Laredo Tugger · 06-13-2021, 08:20 AM

Quote:

Originally Posted by skychief12

Agree with Flybouy.

I'm not seeing that calculations are wrong. I did assume best case rather than worse case. Bottom line is either way loading weights need to be monitored as well as CG.
I'm not sure I'm going to hit 30 degree hills in Texas.

chief,
These guys commenting on here (myself included) just want you to be able to enjoy your trailer safely and be able to load the essentials and travel wherever you wish confidently.
Being on the edge of capabilities and having to monitor your cargo and travel routes does not make your camping experience enjoyable.
Ask me how I know? I was in the same spot your are with a 3/4 ton gasser towing my trailer. After the "consultation" offered on this forum I was enlightened to the strain and safety risk being put on my tow vehicle and adjusted accordingly. Without a doubt you will enjoy your camper and (depending on "life factors") will probably be looking to upgrade in the years to come. So buy a dually now? No not necessarily, but do consider what the future may bring and get the truck tow this future asset safely.
Good luck
RMc

skychief12 · 06-13-2021, 09:55 AM

Quote:

Originally Posted by Laredo Tugger

chief,
These guys commenting on here (myself included) just want you to be able to enjoy your trailer safely and be able to load the essentials and travel wherever you wish confidently.
Being on the edge of capabilities and having to monitor your cargo and travel routes does not make your camping experience enjoyable.
Ask me how I know? I was in the same spot your are with a 3/4 ton gasser towing my trailer. After the "consultation" offered on this forum I was enlightened to the strain and safety risk being put on my tow vehicle and adjusted accordingly. Without a doubt you will enjoy your camper and (depending on "life factors") will probably be looking to upgrade in the years to come. So buy a dually now? No not necessarily, but do consider what the future may bring and get the truck tow this future asset safely.
Good luck
RMc

Exactly. But for now I'll get by just fine. Unfortunately my Duramax was stolen a few years ago after I had sold my 5er, as it worked out.

BTW, good guess "Chief", yes old Vietnam Huey pilot.

merchjo · 06-17-2021, 10:20 AM

I seen lots of these threads and they always talk about the same thing but 1. You see my friend is a lawyer for a large insurance company and he gave me a prospective that i never thought about before towing my RV. He told me you need a minimum 1 million of liability on your rig as that is what the average claim is if you get in a accident and someone is hurt or killed. Second if you are in a accident and there are injuries they will verify the weights of your rig and if they find you over weight they can and will not cover you for that accident. There is a clause in most carrier policies that states that, you know the really fine print. That means you be on the hook personally. Even if you have a umbrella policy, that only kicks in after your primary coverage and if that coverage wont cover you, neither will your umbrella. I had a 31' trailer that's max weight was 7000lb and loaded with propane, battery, water and our stuff the tongue came 1050lb. When we drove it to the scales loaded our payload was a total 1727lb or about 200lb over limit. When I talked to my friend and showed him the scale weights he said if I was his client they would not cover it if I was in a accident. Being I live on the east coast with the amount of traffic we have, the wife and I decided it was not worth risking everything we had if we did have a accident. So we trade our rig in and got a Premier 19FB which is under ever weight number when fully loaded. Something to think about, and even if the accident is not your fault, they find you over weight they will turn it into your fault. Thats way these companies pay millions of dollars to have lawyers on staff.

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