Front Wheel Steering : Things You Need To Know - Part - I

 

What are the primary functions of a steering system?

The primary function is of steering system is to achieve angular motion of front wheels, to provide directional stability, to provide perfect steering condition, to minimize tire wear and to facilitate straight ahead recovery after completing turn.

 

 

Why the front axle in the vehicles is in I-shaped in center and circular/elliptical at outer ends?

This is because front axle has to take bending loads due to weight of vehicle and torque loads due to braking of wheels.

 

What is stub axle and how it is connected to front axle?

Stub axle is axle that holds the main wheel and it is connected to main front axle by means of king pin. Stub axle may be of four types namely, Elliot, reverse Elliot, lamoine and reverse lamoine.

 

What are different types of wheel alignment?

The different types of wheel alignment are front end alignment, thrust angle alignment and four wheel alignment. In one frame alignment two wheel alignment is acceptable and measurements are taken from frame and is assumed that rear axle is aligned correctly but in frameless vehicles with four wheel independent suspension four wheel alignment is necessary.

 

What is wheel alignment?

The process of positioning of wheel to achieve directional stability, perfect rolling condition and recovery after completing turn is called wheel alignment.

 

What is toe-in and toe-out?

If the front wheels are pointing inward it is called toe-in and if pointing outward then toe-out. Due to this lateral slipping of tires occurs and diagonal wear pattern is formed in tires. Hence we can conclude that excessive toe-in or toe-out results in excessive tire wear, heavy steering and fuel consumption.

 

What is set back?

It is the condition in which one wheel on axle is in front or behind the other wheel in relation to chassis. A set back of less than 6 mm is normal by most of automobile manufacturers. Set back may occur due to collision or due to uneven castor. 

 

What is thrust angle and why it should be zero?

 

The thrust angle is angle between thrust line and longitudinal line of chassis. If it is not zero then it will dog track and steering wheel will not be centered. The condition when all four wheels are parallel to frame is called tracking.

 

What are the factors that influence stability and control of vehicle?

The factor that influence stability and control of vehicle are factors pertaining to wheel, steering geometry, steering linkage and suspension system.

 

What is camber and what is its effect?

Camber is defined as the tilt of wheels from vertical. It is positive if top of wheel is tilted outward and negative if tilted inward. Positive camber helps in increasing straight ahead stability while negative camber resists tendency of wheel to slip sideways during cornering but increases steering effort.

If we talk about its effect then positive camber supports toe-out and tire will wear from outside while negative camber supports toe-in and tire will wear from inside. Initially a car manufacturer provides positive camber so while running camber is zero. 

 

What will happen if the camber of front wheels is not equal?

If the camber is not equal then vehicle will be pulled toward maximum camber. 

 

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