Let’s talk pin weight. Since debuting our new 37RVMILES fifth-wheel collaboration with Sabre, we’ve been getting questions about whether someone’s truck can tow this fifth wheel. And in those questions, I’m seeing lots of hints of misunderstanding or uncertainty about what a fifth wheel’s pin weight is, and how it relates to what your truck can tow, or more accurately, your truck’s payload rating.

So, we’re going to cover some real basics for beginners, but if you already own a fifth wheel or you’re well versed in towing, there may be a few nuggets of information in below you hadn’t thought of before. 

Prefer to watch this information on pin weight?

Pin Weight vs. Tongue Weight

If you’re a new fifth-wheel owner or a prospective fifth-wheel owner, you may only have experience with conventional travel trailers, or maybe you’ve never towed before at all.

A conventional travel trailer connects to a ball behind your tow vehicle’s bumper, and most of the weight of the trailer rides on the trailers own axles. Only about 10% gets transferred to the truck. We call this tongue weight, and every tow vehicle has an allowable tongue weight. 

A fifth wheel trailer has an upper deck that rides over the bed of the truck, and the trailer attaches to a hitch in your bed that rides directly over the axles of the truck. This allows for several things: you get a better towing experience—there are virtually no sway issues with the pivot point directly over the truck axles. Your total length driving down the road is shorter by a few feet than if you were pulling a conventional travel trailer of the same length, and the truck’s axles can share more of the weight of the trailer with the trailer axles. 

Two Main Forces

There are two main forces we’re dealing with when we’re towing – the horizontal force – how much weight the engine and transmission are pulling down the road, and the vertical force, or how much weight is being placed on the axles, tires, and suspension. 

The allowable horizontal force determines your truck’s tow capacity, and that vertical force determines your payload rating. 

What is a Kingpin?

The attachment point of a fifth wheel is called the kingpin. The kingpin is a steel pin that extends below the trailer’s upper deck, and connects to the fifth wheel hitch in the bed of the truck. The amount of vertical load pushing down on that kingpin is your pin weight. And it’s the most important thing we’re concerned with when we’re trying to figure out if a truck has the payload rating to be able to handle our fifth wheel.

The Weights of Your Fifth wheel

When you go to the website of an RV manufacturer, you’ll see each model will have listed an unloaded vehicle weight, or UVW, and a pin weight, or hitch weight as it’s often listed.

This is our Sabre 37RVMILES fifth wheel – and these are the weights of the units as they come of the line from the manufacturer without any of your stuff in them. They actually do put them on a scale to come up with these numbers. So it’s really important to understand these numbers do not include all of the gear and food and clothes that you carry with you. That all adds up quickly. 

Cargo carrying capacity is the allowable amount of weight a trailer can carry on top of the unloaded vehicle weight. Add the two together, and you get the Gross Vehicle Weight Rating for your fifth wheel trailer, or GVWR, which isn’t on this webpage, but you will find it on a sticker on your RV. This is the maximum amount your trailer can weigh loaded down with cargo. 

Matching Your Fifth Wheel With a Truck

So, how do we find out if a truck can tow this trailer?

Well, first off, we need to know how much weight we are going to need to carry. And unfortunately, unloaded vehicle numbers aren’t going to help us, and that “hitch weight” or “pin weight” listed on the RV manufacturer’s website is an unloaded number. 

When an RV manufacturer builds a fifth wheel, they design the floorplan, and then the engineers take all of the estimated weights of the walls and cabinets and appliances and roof…everything…and they determine where to put the axles. They’re aiming to place the axles so that the trailer axles carry about 80 to 85% of the trailer’s weight, while the pin transfers the rest to the bed of the truck. They usually end up with a pin weight somewhere between 15% and 20%. So when you look at the unloaded weight of the Sabre 37RVMiles, it’s 13,183 pounds. The hitch weight is 2235 pounds, which is about 17% of the weight on the pin unloaded. 

So I can take that 17% and apply it to the GVWR and assume that the actual pin weight loaded will be 2760 lbs – if I load the trailer to capacity and if I load the trailer evenly. That second “if” is a big “if” because the kitchen, all the exterior storage, and the water tanks are all forward of the axle on this unit and a lot of units. So if I did load to 3000 lbs, my pin weight would likely be even higher. But we’re trying to get the best estimate here because we won’t know our accurate pin weight until we’re loaded down and can weigh it. 

What I suggest most people do is just plan on the hitch weight being 20% of the GVWR.

This is real easy to do when you’re looking at fifth wheels on a website or in person, take the GVWR, multiply it by 20% and you’ll have your estimated pin weight – so for us that’s going to be 3247 lbs.

The Truck’s Allowable Weight Capacities

You can find the “tire and loading information sticker inside the driver door jamb. It will show you your allowed payload. You also have to subtract anything you add to the truck, including passengers, towing equipment like the hitch, and any gear in the bed of the truck.

If you don’t have a truck yet, you might be thinking – do I need a half-ton, ¾ ton, a 1-ton, or a dually—unfortunately, it’s not as simple as that because different truck configurations weigh different amounts.

A crew cab 4×4 truck will have less payload than a standard cab 2-wheel-drive truck, even if they’re both F-350s because there’s less weight on the truck to start with. A diesel engine can tow more than a gas engine, but a gas engine will give you more payload because it’s lighter. You’d think a long bed truck would have less payload than a short bed because the bed weighs more, but the longer wheelbase actually improves your payload. You have to look at the individual truck with all the options and see what the payload will be. 

Luckily, truck manufacturers are making this stuff slightly easier. You can now go to Ford’s website, and there’s a towing calculator.

It shows me your Truck’s gross vehicle weight rating, which is the max the truck can weigh, the maximum gross combined weight rating, which is the max the truck and trailer can weigh together, and my max payload. And then it has fields for added weight that you can configure and find out if you are under your payload rating.

Other Truck Weight Rating Concerns

There are a few other things we need to be concerned about. We need to ensure we’re not over the axle rating on the truck. It’s going to be marked on another vehicle’s door sticker. And we want to ensure that we’re under the load rating on the truck’s tires. The tires should be fine as long as you’re within your payload and you haven’t changed your tires’ load range, but you should check them anyway.

And we’re going to check all of that after we purchase the fifth wheel, after we load it with all of the gear that we want, all the propane and water, by taking it to get weighed. 

Weighing Your Truck and Trailer

To weigh your rig, you want to find a CAT scale, these are at lots of truck stops, don’t be afraid of them. I suggest you download the app, and then you can avoid going in and getting a weigh ticket and paying at the desk.

All you have to do is pull onto the scale. Your truck’s steer axle will be on one section of the scale, your rear axle will be on another, and your trailer’s axles will be on a third section of the scale. You pay in the app, usually around $12, and it will spit back the weights on each of those axles.

You want to make sure that both of the truck’s axles are under the axle rating listed on the sticker inside your vehicle doorjamb and that the total weight on the truck (the steer axle and drive axle combined) doesn’t exceed your truck’s allowable Gross Vehicle Weight Rating—also on the sticker. You want to make sure that the total weight of the truck and trailer together is under your truck’s gross combined weight rating or GCWR.

You then want to go disconnect your trailer and come back around and weigh just the truck. Usually, the second weigh is free or discounted,

You can then subtract different sets of numbers to find out how much weight is being added by the trailer to the truck and how much the trailer weighs itself loaded down with all your stuff. That way, you can find out if you need to re-balance where things are loaded, and you can find out if the trailer is above its GVWR and if you need to shed some weight.

You can even go to some RV shows or rallies where some companies will weigh each tire to help you find out if you are too heavy on one side or another. 

Conclusion

All in all, just try and not cut it close. Estimate, give yourself room, and weigh to make confirm.  Even though being right at your  towing capacity or payload capacity might be legal and allowable by the engineers, your trailer will ride a lot better and you will have less wear and tear on your suspension if you give yourself a 20% cushion.

If you’d like to run the numbers yourself without using your truck manufacturer’s website (which can be clunky), here’s a great website that allows you to fill in the numbers.

Happy towing!