Learning the ABCs
A Glossary of Terms for Cars

By Ashley Bradish

When I started working at Quality Automotive, I knew very little about cars. Four months later, I've gotten a lot more knowledgeable. But I still have a long way to go.


So I figured, "If I don't know much about cars, a lot of people my age may not either." Now, I don't have enough experience to give you all a complete lesson... yet. So, for now, let's just stick with some terms I've learned about so far.


Let's get started on some ABCs! These are some terms I've come across during my time here at Quality Automotive. You may find some familiar, some silly, and some that you might never have thought of before.

Here we go!

Aspect Ratio

A tire's Aspect Ratio is the two-digit number after the slash in the tire's size. For example, in a tire that is P215/65 R16, the "65" means that the tire's height is 65% of the width. The higher the Aspect Ratio, the bigger the tire's sidewall. The lower the Aspect Ratio, the shorter and wider the tire.

Ball Joint

These are spherical bearings with a stud and socket in a metal casing. They are primarily used in front suspensions. The bearings connect to steering knuckles, sort of like the socket joints of four-legged animals. Motion-controlled Ball Joints have a spring on the inside to help prevent problems with vibration in the linkage. You can find Ball Joints on practically every car.


The Chassis is the load-bearing part of the vehicle's frame. It is the main supporting structure where all other components get attached. Think of it as your car's skeleton!


DVI stands for Digital Vehicle Inspection. DVI's involve taking photos of a vehicle's components and assessing their condition.

Quality Automotive performs DVI's with every appointment and sends you the findings! You can read more about DVI's in our blog here.

Engine Control Unit

The ECU controls fuel supply, fuel-to-air ratio, ignition, idle speed, and more! Newer ECUs include even more features like cruise control and anti-skid brake control.


A heavy spinning wheel attached to a rotating shaft to increase the vehicle's momentum. It is essentially a battery that saves kinetic energy. This smooths out the delivery of power from the motor to the vehicle.

Glow Plug

A device that allows combustion to work better in the cold. Glow Plugs are like spark plugs. But rather than "sparking" ignitions in gas engines, Glow Plugs heat up the air and fuel to start the engine. Every diesel engine will have a Glow Plug for each cylinder.


A metal cap fitting onto the hub of a wheel that prevents damage from dirt, rocks, and other debris. Less damage means a longer lifespan! Hubcaps also protect your bolts and nuts from rust and corrosion.

Intake Charge

Intake Charge simply refers to the mixture of air and fuel that flows into the engine.


Possibly my new favorite word, Jounce, is the inward reaction of the spring and shock absorber when a tire hits an obstacle. In other words, it's when the car bounces. Yes, that's right- Jounce = bounce.

Knock Sensor

The Knock Sensor mounts onto the engine and picks up on vibrations, known as "knocks" or "detonations." The Knock Sensor sends signals to the ECU so the computer can determine if the ignition timing should be adjusted. Engines with a Knock Sensor have reduced fuel consumption and increased torque power.

Lock Up

The point at which a tire starts to skid during braking. You know your vehicle is experiencing Lock Up when your wheel has stopped turning and is sliding. To stop it, let off the brake pedal.


It is a construction where the body and the Chassis are a single unit. Monocoque also refers to modes of transport like planes and rocket ships, where the outer skin bears all or most of the stress, just like an eggshell. Monocoque is actually French for "single shell."

Neutral Safety Switch

Neutral Safety Switch prevents your car from starting unless you are in neutral or park.


Describes an engine whose piston diameter is longer than its stroke. Stroke refers to the distance of a piston's movement in a cylinder.

Panhard Rod

Limits the side-to-side or lateral motion of the wheels relative to the vehicle's body. The Panhard Rod, or Panhard Bar, is a bar across the undercarriage that connects the end of an axle to the body at the other side. When making turns, the Panhard Rod keeps the rear axle in place, keeping the wheels aligned with the driveshaft and center of the vehicle. Vehicles with independent rear suspensions do not need a Panhard Rod.

Quarter Panel

The Quarter Panel is the section of a vehicle from the rear door to the trunk. For two-door cars, it still runs from the door to the trunk.


No, not like in the dating world. It's the action of a shock absorber springing back to its fully extended state. The opposite of Rebound is Jounce.


A metal dish under the crankshaft and at the bottom of the engine block that oil drains into. The Sump holds and cools oil while it's not circulating the engine. You may know the Sump as the oil pan.


To put it simply, Tumblehome describes how much a vehicle curves from its sides to its top.

Universal Joint

Universal Joints are little X-shaped hinges commonly used in shafts that relay rotary motion. They allow the driveshaft to connect to the transmission and rotate. Universal Joints help transfer a rotating motion to the back wheels in a rear-wheel-drive vehicle. Since they have a flexible adapter at the driveshaft ends, the driveshafts can move up and down while going over bumpy roads.

Viscous Coupling

A Viscous Coupling is a device made up of plates with holes and slots that transfers torque and rotation through a viscous fluid. They link the front wheels and the back wheels by their axle driveshafts. That way, if one set starts to slip, torque gets transferred to the other set.


A wingnut, or butterfly nut, is a type of nut with two large metal "wings" on each side. These wings make it easier to tighten or loosen by hand without any tools. You can find wing nuts on the axle of your car. And it's just so fun to say!

X-Type Engine

I bet you didn't expect me to find one for X, did you? Well, you're kind of right. While I couldn't find a car part or term that started with the letter X, I did find the X-Type Engine.


An X Type Engine has four banks of cylinders that connect at a common crankshaft. Only two have ever reached production. One was in the 1939-1942 Rolls Royce Vulture Air Craft, and the other was in a 2015 Russian Armata tank!


A Yaw is when you spin out or fishtail. It happens when the weight of the vehicle shifts from the center of gravity to the left or right. It can happen when you hit black ice or hydroplane. Yaws can be dangerous, so it's best to avoid doing those donuts in the parking lot.


A Zerk is a metal fitting on a car's wear points (most commonly on wheels) to allow lubrication. It opens under the force of the grease lubricant and then closes when the grease gun is removed. It's a great way to keep dirt and other contaminants out. Zerks are still around but have mostly been replaced by sealed bearings.

Those are all the terms I have to share with you, for now. I hope you enjoyed reading and learned something about the automotive world!