Steering Gear Ratio

3.9 Steering Gear Ratio or Reduction Ratio:

It has been defined as the “number of turns on the steering wheel required to produce on turn of steering gear cross shaft to which the pitman arm is attached. Generally it varies between 14'.1 and 24'.1.

Fig 1: Rack & Pinion Gear Arrangement

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.

In the 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.