Ask Joe Mechanic: Steering and Suspensions

In the next few issues, I plan to discuss two inter-related systems, steering and suspensions. These components work hand-in-hand to control the movement of a vehicle down the road. I am going to explain the different types of steering and how they work and the same with suspensions.  I will also detail the things that need to be checked and maintained.

            The purpose of the steering system is to enable the vehicle to be pointed in the desired direction at all times. This is accomplished by using a steering box, which is connected to the wheel by a system of arms and linkages to the hub, and spindle on which the wheel and tire are mounted. A predetermined pivot point ahead of the center plane of the wheel, called the caster angle, allows the steering to be self-centering. 

            Another important control feature is the camber angle of the wheel. This is the vertical angle of the wheel and tire in relation to the road and aids in turning. A positive camber means that the top of the wheel is set outwards from the bottom wear as negative

camber means the top of the wheel is tilted inwards. The third component steering angle is toe-in. This is the horizontal angle of relationship between the two tires; with positive toe meaning the wheels are adjusted to point slightly toward each other and negative meaning the tires point slightly outward. These are the three adjustments, which aid in steering a vehicle in the correct direction and also are designed to maximize tire life. If any of these are out of specification, either by age/part fatigue, wear, or due to hitting potholes etc., this will affect your vehicle control, especially under adverse conditions and will also increase tire wear.

            The most popular type of steering in use today is the rack and pinion type. This has nearly replaced the recirculating ball type, which was in use for many years and is still used in some larger trucks and busses. The recirculating ball type used a large circular or “worm” gear, which was on the end of the steering column; this turned another gear called the sector gear. Resistance was reduced by the use of ball bearings to reduce the friction between the gears. The one weakness of this system is a “dead spot” or slight bit of play in the on center or straight-ahead position. This bit of play is required so that the steering will not bind when turned hard to either side. This play is not present with a rack and pinion system, but the recirculating ball type is adjustable to keep the play to a minimum.

            A rack and pinion steering uses a beveled pinion gear to mesh with a rack gear, which is created from a round bar of steel and has teeth machined into it. This transfers the circular motion of the steering wheel into a linear straight-line motion across the front of the car. This is thereby very precise and gives a very positive feel for the road, even when assisted by power steering. And in many newer cars, the power steering is now speed sensitive where the amount of power assist is reduced as the car moves faster.  The one drawback to rack and pinion steering is that when a steering rack begins to wear, there is no way to adjust out the play, so the rack will need to be replaced.

Next week we will cover 4-wheel and rear-wheel steering and suspensions 101.

Some of the information included in this column was sourced from Wikipedia.org articles regarding the topics of Steering, Camber Angles, etc.