Knowing about TOWING CAPACITY and LOAD RATINGS may oblige you to put Vehicles on a DIET!

Understanding the towing capacity of a tow vehicle you plan to use as well as managing RV weights is critical for your own safety and the safety of others on the road.

If the RV you are selecting is a camping trailer , obviously you will need a tow vehicle.

If you prefer a motor home , you may also decide to pull a dinghy (car) behind.


It is then an obligation to study carefully the loading and towing capacity of all the vehicles you are going to use.

The ratings are provided by the manufacturer for each trailer or motorized vehicle put on the market.

Every conscientious RV traveler will make sure to stay within the limits of the vehicles selected. If you exceed these limits, you are putting everyone at risk and a diet may be necessary to get some weight off your vehicles.

Do not blindly trust the sales person at the dealership who tells you that the pickup truck that you own, has enough towing capacity to pull the huge 5th wheel trailer that he/she wants you to buy.


Check yourself if you are within the limits of your vehicles!

FIRST:

Find the factory ratings to calculate the towing capacity. Keep in mind that these numbers are simply estimates or averages in order to give you an idea.

SECOND:

Physically bring ALL your vehicles to a road scale, loaded like if you were traveling and get the ACTUAL WEIGHTS to do the final calculations and have peace of mind.

Let's look at some figures!



LOAD RATINGS (WEIGHT):

What you want to know is how much "stuff" ( load ) you can put in an empty vehicle.

The manufacturer provides ratings to help you figure it out.


- the Gross Vehicle Weight Rating (GVWR) (a constant figure)

It is the maximum allowable weight that a motorized vehicle or trailer can weigh when loaded.

It includes the weight of the vehicle itself plus:

A full tank of fuel, all fluids, all fresh water or other tanks as applicable, all options in the particular vehicle, driver/passengers, cargo, and trailer tongue or pin weight (in case of a tow vehicle).

In other words, this is the most that a motorized vehicle (motorhome or tow vehicle) or a trailer should weigh fully loaded.

The GVWR is provided by the manufacturer and is a CONSTANT figure that is attached to the vehicle unit. It can not be changed. It is the one that will inform you if you have the right vehicle for your needs.


If the Gross Vehicle Weight (GVW) or actual weight exceeds the manufacturer's maximum rating ( GVWR ), you have too much load, being at risk and illegal.

Naturally, the GVW varies all the time depending on the load you add to your vehicle and sometimes a diet is necessary.

Before going to the scale, you can also look at two other figures provided by the manufacturer.


- the Curb Weight (CW)

Each manufacturer may define it slightly differently.

Normally, it refers to the actual weight of a vehicle with a full tank of gas, all oil and water fluids or a trailer with full fresh water tanks, full propane bottles, and all other equipment fluids.

The manufacturer's CW ratings are normally based on standard equipment and do not take into account optional equipment added to the vehicle or trailer.

Check carefully how each manufacturer defines their CW. Normally, it is before taking on any person or personal cargo.

This is important in order to get an idea of the payload allowed.


- the Payload

Knowing this rating beforehand will help you to have an idea of what is allowed in terms of maximum load for the passengers and cargo in any particular vehicle or trailer.

The payload is derived by subtracting the CW from the GVWR. In other words, the difference between a vehicle with standard equipment and the maximum allowed weight of the vehicle on the road fully loaded.

Here is the formula: PAYLOAD = GVWR - CURB WEIGHT (CW)

Now you have a better idea of what is the maximum amount of weight that can be added as a load (driver, passengers, pets and cargo) to each vehicle you are using when RVing.

For a tow vehicle (a vehicle pulling another), you will have to do more calculations to verify if you are within the limit of the towing capacity. This includes dinghy towing.

The manufacturers of motorized vehicles will have a towing capacity for their products.

This is the maximum allowable weight that the vehicle used as a "Tow" can pull. It is usually based on a payload in the vehicle that includes an average-size driver and a full tank of fuel.

As more load is added to the tow vehicle itself (cargo, passengers, gear etc...) the towing capacity drops.

For pickup trucks, you may have two numbers: one to pull a conventional trailer on a ball hitch and another for a 5th wheel trailer hooked on a pin hitch in the pickup box.

These figures give you an idea but they have to be used with the:



GROSS COMBINED WEIGHT RATING (GCWR): (constant)

It is the maximum allowed combined weight on the road of the tow vehicle and the toads with passengers and cargo.

This is very important to understand and it is often where the problem occurs. You may have a pickup truck which has the towing capacity to pull a fully loaded RV but is short when we calculate the GCWR.

Some RVers look only at the towing capacity of the tow vehicle without realizing that it decreases with an increased load in the "Tow" and also that their combination does not respect the GCWR provided by the manufacturer.

The GCWR is a function of the torque output of the engine, the capacity and ratios of the transmission, the capacity of the driving axles and tyres, and the ability of the chassis to withstand that powertrain torque.

Note that:

The Gross Vehicle Weight (GVW) of the tow vehicle plus the Gross Trailer Weight (GTW) of the trailer(s) pulled ( added all together ), should never exceed the Gross Combined Weight Rating (GCWR) of the tow vehicle which pull the trailers.

The GCWR is the most that the entire recreational vehicles, the tow and the toad(s) should weigh attached together.

This means it includes the tow vehicle, trailer, anything towed behind the trailer, and everything inside and on top. This rating is set by the vehicle manufacturer and is a CONSTANT figure.

I hope you are still with me.

In summary:

  • the Gross Vehicle Weight (GVW) or actual weight must be lower than the the Gross Vehicle Weight Rating (GVWR) for all your vehicles (tow and toads)
  • the towing capacity of the tow vehicle must be respected
  • the Gross Vehicle Weight (GVW) of the tow vehicle + the Gross Trailer Weights (GTW) of all trailers towed must be lower than the Gross Combined Weight Rating (GCWR) if you are towing.


There is more!

You also have to check the Gross Axle Weight Rating (GAWR)

It is the maximum weight supported by a vehicle axle or the maximum Gross Axle Weight (GAW) allowed by the manufacturer.

You have two ratings, one for the front axle FGAWR and the other for the rear axle RGAWR. It shows the importance of distributing as evenly as possible the load in the vehicle.

For 5th wheel trailers, where there is a lot of load over the rear axle of the "Tow" because of the king pin hitch in the box of the pickup, the RGAWR is very important and should not be exceeded.

This is the reason for the need to pull big 5th wheel trailers with rear double wheels pickup trucks (DRW) because of much higher capacities.

The manufacturer of the 5th wheel trailer will give you an estimate of the king pin weight in the specifications. Do not forget that this king pin load must be part of the maximum payload of the tow allowed within the GVWR requirements.

For the tongue weight of a conventional trailer attached to a hitch ball, we consider that 10-15 % of the Gross Trailer Weight (the actual weight of the trailer loaded) must be part of the Payload of the "Tow" vehicle, still respecting the GVWR.


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