Episode 174 – Payload

By on March 31st, 2021

In this week’s episode, the topic is Payload – one of the five vehicle characteristics that affect the principal and passengers’ safety and security.   

This is a scenario that all Security Driver and Secure Transportation providers are familiar with; the Principal travels to a location and is met by a Security Driver. The Principal and two other executives will be transported in an SUV. Their luggage is stored in the rear of the vehicle.

Depending on the number of passengers and the weight of the luggage, we now have a scenario where the driver is driving a vehicle with different operational characteristics than the one they arrived in. What created the change is the vehicle’s payload. 

Listen to the Podcast

In a past ISDA Podcast, we covered the Five Vehicle Characteristics that Affect the Safety and Security of the Principal.

They are:

  • The vehicles maximum payload capacity
  • The Tires load rating.
  • Tire Pressure
  • The vehicles SSF
  • Center of Gravity

The wrong combination of these five characteristics can and has proven to be dangerous. The wrong combination is defined as;

  • The vehicle’s payload is at maximum or exceeded
  • Low Tires Pressures
  • Tire Load Rating exceeded
  • High Vehicle Center of Gravity
  • A Low Vehicle Static Stability Factor (SSF)

Definitions

All Vehicle manufacturers devote a great deal of effort and testing to determine the maximum amount of weight a vehicle can carry and stay safe and remain functional.

The amount of weight a vehicle can accept and still supply safe and secure transportation is set by the Vehicle manufacturers.  There are three numbers a security driver should be aware of.

  • Curb Weight
  • Gross Vehicle Weight Rating – GVWR
  • Payload

These are the automotive terms that define the vehicle’s ability to accept the weight of  – passengers, cargo and also are used to determine how much armor a vehicle can accept.

Curb Weight

Curb weight is how much the vehicle weighs on its own, without any cargo or passengers. This measurement includes a full tank of gas and any other fluids that keep a car running. The vehicle manufacturers set that number, and it can be found in the owner’s manual.  

GVWR

Gross Vehicle Weight Rating is the maximum allowable weight of the entire vehicle, including the weight of the vehicle itself (Curb Weight), and any cargo, passengers.

Its manufacturer determines a vehicle’s GVWR, and you can also find that number in the owner’s manual or on the vehicle’s doorframe, near the door latch. You can also find a vehicle’s GVWR on various Web sites.

A simpler explanation is Curb Weight is the weight of the vehicle with nothing in it. The Gross Vehicle Weight Rating is the Curb weight plus the weight of luggage, equipment, or armor plus people that you can add in and to the vehicle (in pounds or kilograms) before it becomes a hazard to drive.

Payload

Payload is defined as the combined maximum allowable weight of cargo, occupants, and optional equipment that the vehicle is designed to carry. Payload is an indication of how many passengers and cargo the vehicle can accept. The vehicle manufacturer also sets that number as it is vital to the safety and security of the passengers.

If the payload is exceeded, it will affect the vehicle’s day-to-day performance and the vehicle’s longevity. There have been scenarios where an armored vehicle is rendered inoperable in a time span measured in months.

If the payload number is exceeded, it will affect the vehicle’s capability to do the simplest things like go, stop, and turn, and in an emergency, it will severely affect the driver’s ability to maneuver the vehicle.

Somewhere on the vehicle, there is a sticker that will supply the payload numbers, or you can also use Google to find the payload of your vehicle. As an example, if you want to find the payload of a Suburban, you type in “Payload for Suburban.” If you did, you would find that the 2021 Suburban has a payload of 1884 lbs. or 855 KG.

If you type in “Payload for a 2021 Tahoe”, you will find it has a payload of 1927 lbs. or 874 KG.

In our scenario, if the vehicle being used is a Suburban, they could transport 1884 lbs. or 855 KG of people or things.

Using the Suburban as an example, if you had four passengers each weighing 200 lbs. or 91Kg plus a 200 lbs./91Kg driver and 100 lbs. or 45 Kg of luggage, you would have 1100 lbs. or 499 Kg of cargo, which would be under the 1884 lbs. or 855 KG vehicle’s payload.

Suppose we change the vehicle to a Mercedes-Benz 500 SEL. We would find that the vehicle’s payload is 1334 pounds or 603 Kg. If we put in four 200 lbs./91Kg passengers and 100 pounds or 45 kg of luggage, we would have 1000 lbs. or 453 kg of payload, leaving us 334 lbs. or 151 kg for additional weight.

Keep in mind that the payload weight is resting on the tires. As we discussed in last week’s episode, the tires are carrying the weight of the vehicle. However, those numbers we computed are for the vehicle at a standstill (“static”).  Since a vehicle is a weight transfer machine meaning when we go, stop, and turn, the weight moves from front to rear, rear to front, and side to the side, the weight on the tires will change.

For example, you’re driving up to a red light, and you slow the car down; as you do that, you are applying roughly 0.3g to the vehicle to stop it, which means you’re transferring weight from the back of the vehicle to the front of the vehicle as you brake. At 0.3g, you will transfer about 20 to 30% of the weight from the vehicle’s back tires to the vehicle’s front tires. So, the payload isn’t static. The payload is moving back and forth. And the higher the Center of Gravity (especially SUV’s), the more the weight transfer.

Those who have been to an old Scotti School or present VDI training program have experienced while in an emergency braking exercise .9 G’ of braking and have witnessed 75 to 80% of the vehicle weight on the front tires. With our scenarios both with the Suburban and the Mercedes, the additional payload supplied by the passengers and luggage, the weight on the front tires has exceeded its limit.

Armored Glass and Vehicle Payload

Now consider that you add the weight of armor to the payload scenarios I mentioned. If 600 lbs. or 272 Kg of armor is added to all those scenarios, in every case, you would be over the payload before moving the vehicle transfer weight.

To determine if a vehicle can accept the additional weight of armor, look at the vehicle’s payload capability. As we mentioned, the payload is an indication of how much armor the vehicle can accept. Taken one step further, it is an indication of what vehicles can be armored to what level. Because of the armored glass’s weight, you are stretching the payload limit when armoring vehicles to a high defeat level.

The problem many times is appearances. One would assume that if an SUV was huge and had a large cargo area, you should add armor without worrying about overloading the vehicle. But that’s not always the case. Some SUVs are huge, have a large cargo area but a relatively low load-carrying capacity.

What can happen if you exceed the vehicle’s payload?

A vehicle that grossly exceeds its payload capacity will be hard to maneuver, stop, and accelerate. The exceeded payload will also decrease the car’s life expectancy and make it more susceptible to blowouts.

Improperly loaded vehicles or those that exceed the weight rating will have a dramatic effect on performance. Steering, maneuverability, braking, and acceleration are all affected. More importantly, stopping distances are dramatically impacted. Simply stated, an overloaded vehicle requires more distance to stop. Security Drivers can misjudge stopping distance when a vehicle is improperly loaded.

Built-in safety mechanisms such as ADAS that help you maintain control of your car at highway speeds may not work as well when you exceed your payload.

Emergency maneuvers will overload the tires exceeding their weight carrying capability and easily create a rollover scenario.

If you have interest in going much deeper into these types of topics, I invite you to check out the International Security Driver Association’s website ISDACenter.Org and consider joining the membership to gain access to the encyclopedia of executive protection and secure transportation – The ISDA knowledge center.

The knowledge shared encompasses a wide range of executive protection and secure transportation focused topics with resources, information, and metrics.

For more information on all of the member benefits, head over to https://isdacenter.org.

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