Let us discuss about a Rack & Pinion type steering gear, which is manual type (that is not a power steering system)
So, a rack-and-pinion gearbox does two things:
- It converts the rotational motion of the steering wheel into the linear motion needed to turn the wheels.
- It provides a gear reduction, making it easier to turn the wheels.
It takes three to four complete revolutions of the steering wheel to make the wheels turn from lock to lock (from far left to far right).
Understanding the terms like Steering Ratio and Gear Ratio:
The steering ratio is the ratio of how far you turn the steering wheel to how far the wheels turn. For instance, if one complete revolution (360 degrees) of the steering wheel results in the wheels of the car turning 20 degrees, then the steering ratio is 360 divided by 20, or 18:1. A higher ratio means that you have to turn the steering wheel more to get the wheels to turn a given distance. So, there is less effort required because of the higher Gear Ratio.
On the other hand, lighter, sportier cars have lower steering ratios than larger cars and trucks. The lower ratio gives the steering a quicker response which means that you don’t have to turn the steering wheel as much to get the wheels to turn a given distance, which is a desirable characteristic in sports cars. These smaller cars are light enough that even with the lower ratio, the effort required to turn the steering wheel is not excessive.
What is a Variable-Ratio Steering, then?
Vehicles that have variable-ratio steering, use a rack-and-pinion gearbox that has a different tooth pitch (number of teeth per inch) in the center than it has on the outside. This makes the car respond quickly when starting a turn (the rack is near the center), and also reduces effort near the wheel’s turning limits.