Home » Technology » Auto Maintenance » Steering & Suspension-Part 2

Steering & Suspension-Part 2

© Garth R. Smith

You know how to steer your car, but what makes the wheel turn the direction you want? The steering and suspension systems in a vehicle are made up of many parts which must all work together for proper steering and handling.

There are two major types of steering and suspension systems. The first, and oldest, is the parallelogram system. This system is usually found on larger, rear-wheel drive vehicles. In this system the steering wheel shaft connects to the frame-mounted steering gearbox. As you turn the wheel it turns the gears in the gear box and transfer the energy to turn the pitman shaft. The pitman shaft is connected to the center link, or drag link, which is a long metal rod running perpendicular to the cars centerline. The idler arm connects to the right side of the center link and is bolted to the frame. It acts as a pivot point for the steering. On each end of the center link is an inner tie rod and outer tie rod which connects to a steering knuckle. The steering knuckle is what the wheel is mounted to and is held in place and pivots on upper and lower ball joints. The ball joint in turn are pressed into the upper and lower control arms which are connected to the frame. Between the control arms is a steel coil spring and a shock absorber which contribute to ride comfort.

If this sounds like a lot of parts, it is. And they must all work together to steer the car and keep it tracking properly. Also, with the exception of the steering knuckle, they are all susceptible to wear to some degree. Shocks are the most commonly worn items and may only last 20,000 miles, especially if you drive on rough roads. Worn shocks can cause harsh ride and tire wear. Because they are load bearing parts ball joints and control arm bushings can wear out fairly quickly. These parts when worn can cause adverse tire wear and a popping noise in the front end when braking or driving over bumps. Worn tie rods most commonly cause a feeling of looseness or vibration in the steering.

The other major type of steering/suspension system is the MacPherson Strut and Rack & Pinion system. Most normally found on front wheel drive cars and many sports cars it provides for greater response and handling by eliminating the steering gearbox and replaceing it with a rack & pinion unit. This unit transfers steering energy more directly to the wheels through the tie rods which connect directly to the rack & pinion. Other steering parts eliminated are the idler and pitman arms, and the center link. Although there are fewer parts to wear out, rack & pinion units can be costly to replace. The suspension components in this system also change with the replacment of the upper control arm and ball joint and shock absorber by a strut. There is still a knuckle connected to the strut and a lower ball joint.

The copyright of the article Steering & Suspension-Part 2 in Auto Maintenance is owned by Garth R. Smith. Permission to republish Steering & Suspension-Part 2 in print or online must be granted by the author in writing.