Math Formula for Weights

[R & S Woodie]

Just had new 3931FB delivered Monday to a campsite in Arcadia, Florida. Now we have to get truck ordered. We see discussion on weights but we don't see how this formula works. How do we determine hitch weight?
Either the Diesel, 4x4, F3500 SRW or DRW can more than handle the 16,500 GVW of the fifth wheel but what is the formula to determine the hitch weight which will determine if we must go DRW? We had transport tow truck stop at the scale so we do have the weight of just the fifth wheel, plus a separate ticket with fifth wheel and transport truck. Would really appreciate the formula to figure this out. We are coming from a motor home so this is all new to us.
Thanks!!

[mlh]

If the weight of the trailer is 16500 max don’t even worry about it get the DRW truck. If you already had a SRW truck I would have advised try it but since you are buying a new truck don’t get anything but the DRW truck. Just that easy and requires no weighing or math.
Lynwood
Oh, enjoy you new camper and truck when you get it.

[Kyle and Lisa]

Welcome to the forum.

[BB_TX]

The general rule of thumb is that the hitch weight will be about 20% of the total weight. The shipping weight (empty weight) of the 3931FB is listed as 13,586 lbs and the hitch weight (again empty) is 2,530. But add in accessories, provisions, clothing, camping gear, tools, and all the other "stuff" and the total weight can go up quickly. But everyone loads differently. Some take very little. Others take a lot. So that number is impossible to put a number on. Only way to know for sure is to weight it after YOU load it. But if someone else has a similar model and has previously weighed theirs, it could give you an idea of the weight gain.

They just keep increasing the payload rating of the new trucks. 1/2 ton, 3/4 ton, 1 ton don't mean anything any more as far as any real weight rating. Check the weight rating of the truck of interest. It may be that an SRW will work for you. And many tow similar trailers with one. But there are also many who prefer the DRW for the increased rating, even though the SRW may have worked. If the numbers work, then it is a matter of personal preference.

[R & S Woodie]

We have the new rig weight with everything loaded. Since we have been full timing for 15 years and 10 years of that was in a 45' coach, we have way too much stuff that we intend to get rid of. We are looking at how do you actually get the hitch weight figure that everyone is coming up with. Is it just 20% of total loaded fifth wheel weight? We have heard 20-30% so that didn't seem to accurate.
Thanks

[PNW Fireguy]

Rather than playing with rules of thumb or estimates simply weight your truck fully loaded and then weigh the truck and trailer fully loaded. You will get all your axle weights and can simply subtract the rear axle eimpty weight from the rear axle with trailer weight and walla you have your specific pin weight, axle weights, gvw for the truck & trailer and let by not least your gcvw. Easy Peezy done

[BB_TX]

Originally Posted by PNW Fireguy

Rather than playing with rules of thumb or estimates simply weight your truck fully loaded and then weigh the truck and trailer fully loaded. You will get all your axle weights and can simply subtract the rear axle eimpty weight from the rear axle with trailer weight and walla you have your specific pin weight, axle weights, gvw for the truck & trailer and let by not least your gcvw. Easy Peezy done

Except that he doesn’t have the truck yet. Trying to determine what to buy.

[twindman]

Also, the reason for needing the pin weight is to see what the truck and rear axle weight is, which a scale already tells you.

[Arkware]

Welcome to the MOC!

You should have the needed weights to calc the pin weight.
Look at the transport truck & Trailer weight report. It should have Trailer Axles only weight. Subtract the axles only weight from the Total Trailer weight. That will give you the pin weight for your rig.

My Rigs Example:
14,575 Total Rig Weight
-10,425 Axles only weight
---------
4,150 Pin Weight

I'm in the DRW with a 8' Bed club.

When I was in your shoes, (5th wheel newby) I decided I wanted a margin of safety, so if I wanted to haul "extra" stuff in the TV, I could.

Very happy I did...

Safe travels!

[BB_TX]

Originally Posted by Arkware

....

My Rigs Example:
14,575 Total Rig Weight
-10,425 Axles only weight
---------
4,150 Pin Weight
.....:..

Wow. Those numbers are not even close to Keystone published spec numbers of 12,185 shipping weight and 2,880 hitch weight for a 2015 3611RL. Did yours have optional equipment and accessories not in the base?

[Texan]

My hitch weight is 21.5%. I'm at 16,200# and my hitch weight is 3,480#. Most srw trucks are fine as has been stated for towing but the hitch weight is what gets you. If you have the DRW then you can load the wagon and not worry about the truck but be careful about overloading the rv. I have a little more hitch weight now than I did but not worried with a DRW.

[mazboy]

Get either one one ton truck. they both will work, you will just need to decide who and how much you will drive the truck. To me, a drw truck is a pain to park...anywhere.
I'd go with a short box one ton truck.

[CalandLinda]

Originally Posted by BB_TX

Wow. Those numbers are not even close to Keystone published spec numbers of 12,185 shipping weight and 2,880 hitch weight for a 2015 3611RL. Did yours have optional equipment and accessories not in the base?

The RV trailer building instructions (FMVSS) require the trailer manufacturer to provide a recommended tongue/hitch weight. It's required for vehicle certification purposes and reads like this; The trailer manufacturers recommended tongue/hitch weight, when added to the trailer's total vehicle GAWR values MUST not be less than the trailer's certified GVWR.


Once the trailer is sold the owner becomes 100% responsible for its hitch/tongue weight.

In chapter #4 (RV section) of the following reference you'll find all you need to know about getting specific weights at some scales.

https://www.ustires.org/sites/defaul...TruckTires.pdf

[R & S Woodie]

Thank you all so much for the information. Very Helpful! Wanted to make sure we were accurately understanding this process.

Checking F3500, 4x4, 6.7 L Diesel, crew cab short bed, SRW brochure hitch weight of 3950 but door tag of new truck says only 3595. Monty brochure hitch weight for 3931FB says hitch weight of 2530 but a call to Keystone and the actual figure went up to 2610. All the figures are going the wrong way.

If truck hitch 3595 - 2 people/cargo 450 - 267lb hitch - 2610 Monty empty = 268 cargo. Not enough to even add generator let alone cargo.

We previously owned a DRW but did not pull RV with it (work vehicle). We did not want to do that again but we also will be doing a significant amount of traveling all across the country and don't want to be on the edge so may have to go DRW again.

[Arkware]

Originally Posted by BB_TX

Wow. Those numbers are not even close to Keystone published spec numbers of 12,185 shipping weight and 2,880 hitch weight for a 2015 3611RL. Did yours have optional equipment and accessories not in the base?

Hey Bill,

These are my loaded weights measured by the RV Safety crew at the Fall Rally this year. I'm sure you know, Keystone's published weights are for an empty rig. With a Gross weight of 16,000, I'm still within specs.

If I read the OPs post correctly, he also had a loaded rig weighed, so his numbers should be close to reality....

[jeffba]

If you are just going with a swag at the weight prior to weighing. Add about 800 - 1000 pounds the the published pin weight. That will come close to covering you and your spouse, hitch in bed of truck, propane, batteries, power cords, chairs, clothes and what ever you cannot live without while camping. I had a 1T SRW and was at 11400 lbs. Truck was rated at 11500. DW, dogs, Food and future W/D were not included. At the Rally I met a couple of folks with SRW. One was going through tires because of exceeding the carrying capacity of his truck. Another went with a dually because he could not get tires rated for the load.

[knapper42]

Now I'm confused. I have a 3560RL we bought last Jan in Quartzsite and have pulled it with our Ram 2500 diesel. The Cat scales shows my Ram weighs 8560, front 5120 - rear 3440, fully loaded includes BW hitch.
Hitched to Montana shows, front=4880, rear=6280, trailer=10820 making combined 21980.
The truck spec shows gcwr as 25K. so that seems ok
The Pin weight shows to be about 2980. so that's not good because the truck spec say payload is 2150. 830lbs over weight. right?
rear tire capacity is each tire 3560. capable of carrying the payload. also have air bags to take some strain off of the coil spring.

it looks like to me that the total weight are within spec but the payload is exceeded but yet the tires and axle are capable of carrying the weights.

Where the heck do I stand? sorry to be so dumb but after reading all these posts I concerned I'm not traveling safe.

[jeffba]

Originally Posted by knapper42

Now I'm confused. I have a 3560RL we bought last Jan in Quartzsite and have pulled it with our Ram 2500 diesel. The Cat scales shows my Ram weighs 8560, front 5120 - rear 3440, fully loaded includes BW hitch.
Hitched to Montana shows, front=4880, rear=6280, trailer=10820 making combined 21980.
The truck spec shows gcwr as 25K. so that seems ok
The Pin weight shows to be about 2980. so that's not good because the truck spec say payload is 2150. 830lbs over weight. right?
rear tire capacity is each tire 3560. capable of carrying the payload. also have air bags to take some strain off of the coil spring.

it looks like to me that the total weight are within spec but the payload is exceeded but yet the tires and axle are capable of carrying the weights.

Where the heck do I stand? sorry to be so dumb but after reading all these posts I concerned I'm not traveling safe.

"The Cat scales shows my Ram weighs 8560" so if your GVWR is 10000 you have a total of 1460 pounds left over for pin weight. So if your pin weight is 2980 you are actually 1500 pounds over.

[Montana Man]

Knapper42, 3/4 ton trucks are not the vehicle for pulling these big fivers. Some folks do. They certainly have the power but other factors limit the weight carrying capacities as determined by the manufacturer. There is a ton of discussion about this on the board. Safety and liability are the two biggest concerns for me, it is irrelevant to others. It is good to know where you stand in any case.

[The Bone]

If you want to stay with a SRW than make sure you get the 11,500 package. That will give you bigger brakes axles, gear ratios and that should be fine. Go to the Ford site and there is a weight sheet for trucks there. Take the max loaded weight from the trailer sticker and 20% of that max weight should be fine.