Positive caster Vs Negative caster

Positive caster is when the steering axis is in front of the verticle axis and negative caster is when the steering axis is behind the verticle axis. In this article, you have to clear your mind to check it out the difference between positive and negative caster, comparison and much more details about them.  

Difference : 

  • Positive caster occurs when the axis of the steering wheel is ahead of the vertical axis and negative caster occurs when the axis of the steering wheel is behind the vertical axis.  
  • A significant amount of positive caster provided that your vehicle has a well-fitted power steering system while negative caster symptoms make the steering wheel light and increasing the susceptibility of your vehicle, and make its path accurate without proper direction.
  • Positive caster angles run between 3 - 5° on modern vehicles gives a good mix of highway stability and steering feel. Negative caster is opposite to positive caster. 

Summary : 

If you modify the caster settings on your vehicle, make sure that you keep the angular degrees of the casters completely symmetrical with one another. If you make the mistake of miscalculating the angles of the casters on various wheels of your vehicle, then you will find your car will start pulling more towards one side with respect to another side which doesn't have much of a caster angle. 

Difference between caster and camber

Definition of caster angle : 

The caster angle is the angular displacement of the steering axis from the vertical axis of a steered wheel in a car, motorcycle, bicycle measured in the longitudinal direction. In other words, it is the angle between the pivot line and vertical. 

Definition of camber angle : 

The camber angle is the angle made by the wheels of a vehicle, it is the angle between the vertical axis of the wheels used for steering and the vertical axis of the vehicle when measured from the front or rear. 

Camber angle is taken care when designing the steering and suspension.

If the top of the wheel is farther out than the bottom, is called positive camber. If the bottom of the wheel is farther out than the top, is called the negative camber. 

This article is about the caster vs camber, what is caster angle, what is camber angle and comparison between caster and camber.

Difference between the caster and camber : 

  • Caster is the angle between the verticle line and kingpin centre line in the plane of the wheel when the viewed from the side is called the caster angle. Camber is the angle between the centre line of the tyre and vertical line viewed from the front of the vehicle is known as the camber angle.
  • Caster is the steering angle with respect to the wheel's centre and camber is wheel's angle with respect to its centre. 

How to adjust correct steering angle?

The perfect steering is achieved when all the four wheels are rolling perfectly under all running condition. While taking turns, the perfect rolling condition is satisfied if the axis of the front wheels when produced meet the rear wheel axis at one point. Then this point is called the instantaneous centre of the vehicle. 

It can observe that the inside wheel is required to turn through a greater angle than the outer wheel. The larger the steering angle, the smaller the circle of turning. However, a maximum to which we can go as the steering angle. 

It has been found that steering angle can have a maximum value of about 44 degrees. 

The extreme positions are called lock positions on either side. The diameter of the smallest circle which the outer front wheel of the car can traverse and get when the wheels are at their extreme positions is referred to as the turning circle.

Now let we discuss the formula for correct steering angle. 

correct steering angle
Correct Steering Angle

Let the axis of the inner wheels makes a larger angle θ than the angle φ subtended by the axis of an outer wheel. 

Let a = wheel track
b =  wheelbase
c = distance between the pivots A and B of the front axle

From the triangle IBP 

cotθ = BP / IP 

From the triangle IAP

cotø = AP / IP = AB + BP / IP = AB / IP + BP / IP = c / b + cotθ

cotø - cotθ = c / b 

This is the fundamental equation for correct steering.