Steering and braking systems, control system of automobiles. The first two systems can only get the car moving, but the car we want should be an obedient tool. With the steering system and braking system, the driver can control the chassis part, and with the engine, a car can actually run.

Then look back at the four nouns at the beginning of the article. Suspension (note that there is no suspension) refers to a system connected between the girder and the bridge. It includes shock absorbers and necessary braces to ensure the stability of the chassis.

The axle is obviously responsible for bearing the weight, so it should be part of the driving system of the car. And the axle, generally speaking, is the half-axle, which is connected to the axle center of the wheel, responsible for driving the wheel, so it is part of the transmission system. But in many places, axles and axles, sometimes even suspensions, are all about the same parts, which can easily be misleading.

For example, two years ago, a brand car "broken axle door" incident, people do not understand that it is half axle broken, but in fact it is the rear suspension broken.

Postscript:

Looking at this, you may say: a few nouns in a paragraph make it clear that you have to say so much. Yes, you can understand what these nouns mean by looking at the last two paragraphs separately, but if you can take a moment, read this article, compare your car and sort out the structure of the chassis in your mind, you will be as organized as you are when using, maintaining and repairing your car.