Vehicle Dynamics Concepts - Scott Parker

Vehicle Dynamics is a class that I’ve been teaching for several years. The premise is this: vehicles were designed, tested and built to function a certain way. As soon as we start making modification to our vehicles, we are fundamentally changing how they were designed. Modifications are not necessarily a bad thing, but for every change we make, there can or will be a consequence; sometimes this can be good and sometimes it can lead to potentially dangerous outcomes.

During class I usually have the students walk around a modified vehicle. We discuss the modifications and how they affect the handling characteristics of the vehicle, which gives the students a process for deciding a need or want, as well as developing a good sense for unintended consequences. A common example would be: I may want a steel bumper with a winch which could easily add an additional 200 pounds to the front of the vehicle. While the bumper can provide additional protection, the choice of adding a bumper may depend on what I plan on doing with the vehicle. This may be a want and not necessarily a need. Think of it like this, if I add additional weight in the front of a vehicle, I may find it necessary to upgrade my suspension. The vehicle might still be drivable, but the front end may sag, which would decrease my approach angle. Additionally what may have been a $1,500 cost with the addition of a bumper and winch may now cost you additional $1,500 or more to upgrade my suspension. Actions have consequences.

During this class we usually start at the bottom of the vehicle and work our way up, a process which gives us the opportunity to discuss each component and how they affect the vehicle, and whether we should delete, modify or replace components in or on the vehicle. Developing needs and wants can help us prioritize certain aspects of the build, while vehicle dynamics lets us understand the consequences to those actions.

Typically, the first thing I ask students to do is to research their vehicles. They can look in their vehicle manuals and utilize the placard that is typically found on the inside of the driver’s door. We are looking for several important pieces of information, such as what does the vehicle weigh and what is the GVWR or Gross Vehicle Weight Rating, which is how much it can carry, max load. Understanding these two benchmarks will help you determine what you can and can’t do with your build, or more importantly, what you need to modify so that your vehicle can properly function not only out on the trail but during everyday travel as well. While there are other pieces of information

Vehicle Dynamics Concepts

that we will need when building a vehicle, these are two that I find the most important.

Adding things like bigger tires, different suspension and roof racks will fundamentally change how your vehicle performs; these things will change your center of gravity and potentially change your braking distance. As you increase your vehicle’s weight, you may notice that you are wearing through your brake pads faster, which may lead you to needing to upgrade your brakes. My goal is to give students a good working knowledge to be able to think through the process of adding additional gear. I’m not asking you to become an engineer, but having a good understanding of how making one decision can affect another is important.

It is certainly essential to understand that some components on our vehicles are more than capable to handle the day-to-day activities that we will put them through, but when venturing off the beaten path it’s also essential to identify weak points and what common issues we may need to address sooner rather than later. The end goal is to enjoy the outdoors, and by making smart decisions as we build our vehicles, it helps to limit the issues that may arise down the road. Over the next several issues we will dive further into building vehicles and address some of the most common questions that arise.

Scott Parker

I4WDTA Certified Instructor Federal Government Off-road Instructor Member of BOLD Overland

Scott Parker

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