The chassis is the framework to which the various parts of the automobile are mounted. The chassis must be strong enough to bear the weight of the car, yet somewhat flexible in order to sustain the shocks and tension caused by turning and road conditions. Attached to the chassis are the wheels and steering assembly, the suspension, the brakes, and the body.
The suspension system enables the automobile to absorb the shocks and variations in the road surface, keeping the automobile stable. Most cars feature independent front suspension, that is, the two wheels in front are supported independently of each other. In this way, if one wheel hits a bump while the other wheel is in a dip, both wheels will maintain contact with the road. This is especially important because steering the automobile is performed with the front wheels. More and more cars also feature independent rear suspension, improving handling and the smoothness of the ride.
The main components of the suspension system are the springs and the shock absorbers. The springs suspend the automobile above the wheel, absorbing the shocks and bumps in the road surface. As the chassis bounces on the springs, the shock absorbers act to dampen, or quiet, the movement of the springs, using tubes and chambers filled with hydraulic fluid.
The steering system is another part of the suspension system. It allows the front wheels to guide the automobile. The steering wheel is attached to the steering column, which in turn is fitted to a gear assembly that allows the circular movement of the steering wheel to be converted to the more linear, or straight, movement of the front wheels. The gear assembly is attached to the front axle by tie rods. The axle is connected to the hubs of the wheels.
Wheels and the tires around them are the only contact the automobile has with the road. Tires are generally made of layers of rubber or synthetic rubber around steel fibers that greatly increase the rubber's strength and ability to resist puncture. Tires are inflated with air at a level that balances the greatest contact with the road surface with the ability to offer puncture resistance. Proper inflation of the tires will decrease wear on the tires and improve fuel efficiency.
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