Regarding Pin weight and payload

[Blaise1]

We recently got a new 5th wheel trailer - a Grand Design Reflection 311 BHS.

The trailer spec sheet says:
UVW: 11.378 lb (unladen or curb weight)
GVWR: 13,995 lb
Hitch: 2,378 lb (pin weight)

Is the stated pin weight for the unladen trailer or for the fully loaded trailer? It matters because it will affect the payload calculation.

I think it is for the unladen trailer. As you load the trailer, at least some of the load must increase the pin weight, especially when you consider that much of the load is stored in the pass through, toward the front of the trailer - my guess is probably more than half of the load adds to the pin weight.

So, given a 1 ton pickup (Silverado 3500) with these stats (all in pounds):

And given 1,050 lb of truck load: 3 people (700), the weight of the hitch (250) and other stuff loaded into the truck (lets say 100).

SO remaining payload = max payload minus (pin weight + truck load):
4157 - (2378 + 1050) = 4157 - 3428 = 729 remaining payload.

But that's only if the trailer is unloaded. My estimate is a 2000 pound load in the trailer, and maybe 65% of that adds to the pin weight. That's another 1,300 pounds of pin weight, so now the actual payload is 571 pounds over the maximum - the payload (4723) is 114% of the maximum payload.

The other thing is that the max tongue weight is 2745. but the pin weight adjusted for trailer load as above yields an effective pin weight of 3678 - that's 134% of the stated max gooseneck pin weight.

If we do the same calculations with a 3500 dually:

remaining payload = max payload minus (pin weight + truck load):
5851- (2378 + 1050) = 5851 - 3428 = 2423 remaining payload. Subtracting the 1300 lb of additional pin weight (the trailer load) yields 1123 pounds of remaining payload. The payload (4723) is 81% of the max.

But again, the effective pin weight (367 is 138% of the stated max pin weight.

Does this trailer really require a one ton dually? And why is the max pin weight only 2670 when the truck has a max payload of 5851 and an RGAWR of 10,400. All this just seems wrong.

Someone please show me what I'm doing wrong.

Thank you.

 

[CharlesinGA]

The pin weight GM is specifying is the actual pin weight, whatever that may be. Figure 20% or up to 25% of the GVWR OF THE 5TH WHEEL for a reasonable number to use.

You could easily be looking at a pin weight of 3500 lbs

Yes, a 14,000 lb 5th wheel will need a dually.

Charles

 

[RayIN]

Use this online towing calculator to safely match a tow vehicle and trailer. It will accurately and impartially match your trailer to a tow vehicle or visa verse.
It can also prove a salemans line, " this truck can tow anything" inaccurate.
When looking at trailers, the unloaded weight is meaningless unless that's how you plan to travel, with an empty trailer.

 

[Ex-Calif]

And why is the max pin weight only 2670 when the truck has a max payload of 5851 and an RGAWR of 10,400. All this just seems wrong.

I think you are getting confused about how these calculations work. It is beneficial to think of each number as a limit and do some math to reveal the thinking process.

Start with GVWR - Curb ("empty") weight = 5851# - Payload is distributed among the whole chassis and includes front axles, rear axles, gas, people, cargo. So in my quote above it's clear why pin weight is different than payload.

So lets' look at combining the truck with a pin tow.

GCWR - Curb Weight = 17,851 - close enough to reveal the Gooseneck TWR.

So where does the 2670# pin weight come from? It is a guideline that is accepted at 15% for trailer pin weight.

17851 X .15 = 2677# - Why the maker doesn't allow a higher pin weight considering a 5800# payload? One is probably single point structural limits on the bed structure and 2 is more likely that 5851# of payload needs to be distributed among 2 axles (front and rear) and balance is probably an issue.

This is how I break things down. Remember - You have a lot of choices around how you load the vehicle. The maker arms you without enough info to make an informed decision.

 

[Gary RV_Wizard]

Is the stated pin weight for the unladen trailer or for the fully loaded trailer? It matters because it will affect the payload calculation.

GM is stating the actual pin weight they have determined the truck can safely & reliably handle, based on the SAE J2807 tow rating standard.. Whether the trailer is fully or partially loaded makes no difference. ex-Calif explained it in more detail...

Also, be aware that J2807 isn't specific to RV-type trailers and J2807 testing is almost exclusively done with low-profile utility trailers, where wind resistance and top-heavy loads do not come into play.

 

[Blaise1]

Thanks to all for the feedback. A special "thank you" to @Ex-Calif for the detailed explanation. And I apologize for my long-winded explanations and questions.

The trailer's spec sheet has the pin weight at 2378. My assumption is that this is the actual pin weight of the trailer is when it is unloaded. Loading the trailer will obviously increase the actual pin weight. My rough estimate for the loaded pin weight is 3678. This may admittedly be a bit high.

I was trying to figure which truck I needed: 3/4 ton, 1 ton SRW, or 1 ton DRW. All three of these trucks can easily pull the trailer whose GVWR is 13,995.

My concern is the payload. Given 1000 pounds for people, the hitch and stuff, plus the loaded pin weight, the expected payload is 4678

The 3/4 ton payload is 3317. This is not enough to handle the unloaded trailer's pin, never mind the loaded pin weight. The expected payload is 141% of truck max.

The 1 ton SRW payload is 4157. That is enough for the dry pin weight, but not enough to handle the estimated loaded trailer pin weight. The expected payload is 113% of truck max.

The 1 ton dually payload is 5851, and that is enough to handle the expected payload, which is 80% of truck max.

This is why my conclusion is that, while the 1 ton SRW would probably "be ok", the 1 ton DRW is the truck whose capacity is not exceeded.

I would prefer the SRW, because it is more maneuverable, will likely get better gas mileage, and will probably be less expensive to maintain. But traveling cross country with wife and daughter, I just don't think I would feel comfortable with the SRW.

I was hoping to be persuaded that the SRW would easily be sufficient, but that just doesn't seem to comport with the facts.

Thanks to everyone - it is really appreciated.

 

[TonyL]

Whilst I would not like to question your choice or calculations, from what I have learned from this site and 14 years towing fifth wheels in the UK and the US is as follows:
Pin weight is normally between 20 to 25% of gross weight.
Our US fifth wheel has a gross weight of 14375ib , we have never weighed it (I know, naughty) but in 5 years and around 30000 miles of towing, mostly in the Rockies and the west, our srw F350 has never caused us a moment's worry.
We are normally 2 up and anyone who has met us will confirm that we are not lightweights.
We tow with full water tank whenever necessary, spare 10 gallons of diesel, 5 gallons of gas and on occasion needed to take emergency avoidance of other road users without issues.
An SRW has worked for us in real life, just saying, but ultimately it has to be your decision.

 

[Blaise1]

@TonyL Thanks for responding. I appreciate your view, and the tactful way in which you expressed it.

I frequent a couple of Grand Design Facebook groups, one specific to our trailer (GD Reflection 311 BHS). I posed this question there to get feedback from people that have the same trailer. It seems that about 10% use a 3/4 ton; the rest are pretty closely divided between the 1 ton SRW and DRW, perhaps a few more DRW than SRW.

I'm an engineer, so I'm quite comfortable playing with numbers and calculations. But in my experience, the accuracy of results is always heavily dependent on initial assumptions, even if I am using the correct formulas.

As you said, each traveler has to decide what is best for them. Being a "belt and suspenders" kind of guy, I'll probably go with the DRW. I'll put up with it's shortcomings for the comfort of knowing that no matter how much my wife packs into the trailer, we will be entirely within the capabilities of our truck!

Cheers!

 

[CharlesinGA]

Don't forget to add about 200 lbs for the fifth wheel hitch in the bed. Be sure and get a truck already set up from the factory with the puck system in place. Its a big heavy piece of steel and installing it requires removing the bed to do the job right. (though I'll bet a lot of installers loosen the bed and block it up.) I'm a person who will bite the bullet and get something out of the way rather than working around it.

Combination 5th wheel puck and gooseneck ball mounting.

Charles

 

[Ex-Calif]

The trailer's spec sheet has the pin weight at 2378. My assumption is that this is the actual pin weight of the trailer is when it is unloaded. Loading the trailer will obviously increase the actual pin weight. My rough estimate for the loaded pin weight is 3678. This may admittedly be a bit high.

Note that truck limit of 2670 is "maximum" pin weight. It is derived using maximum trailer weight and optimal loading.

2670 / 18000 = .14.83 or close enough to 15%.

So the key here is that 2670 is a maximum limit. You have a choice to load the trailer longitudinally to distribute the load so the pin only has 2670 on it.

Because you can theoretically load the weight and balance of the trailer any way you want. Consider the trailer pin weight as also a fully loaded "goal" with a value not to exceed the trucks limit. Note here that by loading most of the carried weight rearward the pin weight doesn't go up as fast as the axle weights. You should keep in mind the trailer axle gross weights but I think you will find that the trailer axles have capacity so that 85% of the max trailer weight can be accommodated.

The only practical way to achieve the trailer balance is to weigh it. Preferably unloaded so you know that payload you have for the trailer and the unloaded balance. Then after loading it weigh it again.

I weighed my rig using what I call traveling weight - It is a Class A so I had full fuel, 1/2 water, full propane and stocked with my personal items, groceries etc.

 

[Gary RV_Wizard]

Your loading weight estimates seem a bit high to me. Few 5W hitches weigh anywhere near 200 lbs and 1000 lbs is a lot of people & stuff. I'd guess 700 would be a generous estimate for your load. But I'm also skeptical of the payload specs from brochures and websites - they are typically higher tan most real-life vehicles. I suggest you visit some truck dealers and look at the actual federal weight placard in one ton SRW & DRW trucks to get a better feel.

I'm also somewhat mystified about that GM Max Tongue Weight number, which seems to be tied somehow to their SAE J2807 testing. The stated tongue/pin weights seem extremely conservative for the quoted Payload specs. It may be simply the tongue/pin weights of the trailer that was used to get the ratings. Not the maximum the truck could handle. The low-boy style utility trailers used in testing typically have a lower tongue or pin weight than RV style trailers with their high houses up front. In simple terms, utility trailers are balanced differently.

 

[Poop-Pyramid]

We recently got a new 5th wheel trailer - a Grand Design Reflection 311 BHS.

The trailer spec sheet says:
UVW: 11.378 lb (unladen or curb weight)
GVWR: 13,995 lb
Hitch: 2,378 lb (pin weight)

Is the stated pin weight for the unladen trailer or for the fully loaded trailer? It matters because it will affect the payload calculation.

I think it is for the unladen trailer. As you load the trailer, at least some of the load must increase the pin weight, especially when you consider that much of the load is stored in the pass through, toward the front of the trailer - my guess is probably more than half of the load adds to the pin weight.

So, given a 1 ton pickup (Silverado 3500) with these stats (all in pounds):

View attachment 170138

And given 1,050 lb of truck load: 3 people (700), the weight of the hitch (250) and other stuff loaded into the truck (lets say 100).

SO remaining payload = max payload minus (pin weight + truck load):
4157 - (2378 + 1050) = 4157 - 3428 = 729 remaining payload.

But that's only if the trailer is unloaded. My estimate is a 2000 pound load in the trailer, and maybe 65% of that adds to the pin weight. That's another 1,300 pounds of pin weight, so now the actual payload is 571 pounds over the maximum - the payload (4723) is 114% of the maximum payload.

The other thing is that the max tongue weight is 2745. but the pin weight adjusted for trailer load as above yields an effective pin weight of 3678 - that's 134% of the stated max gooseneck pin weight.

If we do the same calculations with a 3500 dually:

View attachment 170139

remaining payload = max payload minus (pin weight + truck load):
5851- (2378 + 1050) = 5851 - 3428 = 2423 remaining payload. Subtracting the 1300 lb of additional pin weight (the trailer load) yields 1123 pounds of remaining payload. The payload (4723) is 81% of the max.

But again, the effective pin weight (367 is 138% of the stated max pin weight.

Does this trailer really require a one ton dually? And why is the max pin weight only 2670 when the truck has a max payload of 5851 and an RGAWR of 10,400. All this just seems wrong.

Someone please show me what I'm doing wrong.

Thank you.

Load up trailer, fill up the truck with fuel and take the family to visit a CAT scale. That will tell you all you need to know. I doubt you need a dually for a 311BHS. Even if you max your trailer at the GVWR, you're looking at the most... 3,500 lbs on the hitch (25% trailer weight on the pin). The BHS has 2,600lb cargo capacity... that is literally a ton of stuff. A CAT scale will tell you, without a doubt, where you are with weight.