Handling Mods: Introduction
Improving the way a car handles without compromising comfort can be incredibly difficult.
DISCLAIMER: As always, follow all safety protocols. Don't undertake this task if you aren't comfortable with it and fully understand it. You are ultimately responsible for anything you do. Neither Redpants, LLC or myself is responsible or liable for anything that may occur.
Beginning with Basics
Although I'm using "handling" as a blanket term that implies turning ability, it actually includes quite a bit more. In fact, the nuances of handling have major impacts on every aspect of a car's performance: zero-to-sixty times, ride comfort, safety, braking, and of course the ability to change direction.
To help ensure explanations and descriptions are clear and understandable for individual modifications, let's start off with the basics of suspension.
Sprung vs Unsprung Mass
Weight can be classified in two broad categories: sprung and unsprung mass. The difference between the two is important to understand as the effect of each on the car can be substantial.
To over-simplify it: sprung mass is any weight attached to the chassis, and unsprung mass is any weight attached to the suspension. The body panels, engine, transmission, seats, and so on, are all attached to the chassis of the car, and these don't move relative to the chassis. The wheels, tires, brake rotors, etc, are all attached to the chassis via the suspension, and they move independently of the chassis.
Sprung mass is the weight of components that are supported by the car's suspension. The weight is carried by the springs of the suspension, thus the "sprung" term. Think of sprung mass as the static bodyweight of the car - the body and everything inside the body). When you take a corner really hard and you feel the car lean to the outside of the turn (body roll), that's the sprung mass (the static weight) of the car maintaining its momentum in the direction the car was going before turning. The more sprung mass the car has, the more momentum the weight will have, and the more body roll there will be. Not only can that be unnerving to feel, it's also bad for performance. If the weight of the car is trying to go outward during a turn, then it isn't going in the direction of the turn.
Reducing sprung mass - that is, lowering the static weight of the car - reduces the amount of momentum the car's weight has when turning. More energy will be put into the turn, meaning the car will turn better.
The concept holds true in straight-line performance. When you accelerate, the weight of the car holds you back. If two cars are identical but one is loaded with an extra couple hundred pounds of cargo, it will accelerate slower than the empty car because less energy is used to move the additional weight. Likewise, when you step on the brake pedal, there's less weight trying to continue moving forward (again, weight has momentum). So a the heavier car will take longer to stop because the brakes (and tires!) have to fight against the momentum of the extra weight.
The important thing to know about sprung mass is that the more you have of it, the more energy goes into controlling the car's weight, and the less energy goes into the car's performance.
The weight of components between the suspension and ground is unsprung mass. That is, it's weight that is not supported or carried by the suspension. It includes the wheels, tires, lug nuts, hubs, brakes, and so on.
The importance of unsprung mass is very different than what we discussed for sprung mass, so try to have an open mind about this section and don't relate it to the Sprung Mass section above until I bring it back up in the following section about Unsprung Rotating Mass.
Unsprung mass directly affects the performance of the car's suspension.
unsprung Rotating Mass
Another broad category, rotating mass is any weight that spins. I discussed the concept as it applies to engine performance and the topic carries over to handling as well, as the wheels, tires, and brake rotors of your car are rotating mass. Not only are these components rotating, they're also unsprung. Because it's both unsprung and rotating, the weight of these components have a much greater impact pound-for-pound on vehicle performance than sprung mass. For example, a 29-lb weight reduction by switching to a lightweight battery doesn't have nearly as much of an effect on performance as the 24-lb weight reduction you can get from a set of lightweight wheels.
Springs, Struts, and Coilovers
The most commonly-replaced parts of any suspension are the springs, followed by the struts. These units assembled together, along with top hats, are called coilovers.
Wheels, tires, and Brake Rotors
For the sake of this introductory explanation, I'm going to lump these into the same category (don't worry, I'll go into each in far more detail later on). Wheels, tires, and brake rotors are both unsprung rotating mass. Reducing weight from them can have a major impact on vehicle performance.
Tire weight is an often-overlooked aspect of tires when it comes to performance.