Steering accounts for about half of your experience driving a restored car. Whether the suspension is hard or soft, whether the engine is powerful or meek, whether the seats are comfortable or Spartan, the driving experience is most powerfully informed by the way the car steers. Good steering is key to enjoying your finished car, so you want to get it right.
Restoring your car’s steering system goes hand in hand with your suspension restoration, and in fact the two systems are most often restored together. As with your suspension, all hard steering parts must be crack-checked using ultra-violet light (often called “Magnaflux” crack checking) before they are returned to your car. Cracked components may be repairable, or they may need to be replaced.
A special case for steering is the steering box or rack. These components are prone to wear and may or may not be adjustable. There are several designs for steering boxes, such as “worm and sector gear,” which is also known as “recirculating ball.” Another design is known as “cam and lever.”
In all these designs, rotating motion from the steering wheel is fed into a system of gears and ball bearings to swing an output arm (called a Pitman arm) through an arc. Steering rods are attached to the end of the Pitman arm and used to turn the wheels. Sometimes, an additional Pitman arm and bearing case (known as an idler arm) is used on the opposite side of the car as the steering box. This allows the car to have two equal-length final steering rods and a central rod between the idler arm and the steering box.
All steering box designs use interacting moving parts, and they tend to loosen up as they wear. You experience this wear as increased play in the steering wheel. Some steering boxes are adjustable to account for wear, while others are not. Rebuilding a steering box is generally a job for a professional, as the play between gears and other components must be set precisely, and bearings generally must be pressed into place.
Sports cars and British imports are more like to have rack and pinion steering. This design is much simpler than steering box designs. The steering wheel turns a small gear (the pinion) which engages a toothed rod. Since the pinion is held motionless, the toothed rod (rack) moves from side to side. Equal-length steering rods attached to either side of the rack are moved to turn the wheels. Like a conventional steering box, rebuilding a steering rack is generally a job for a professional.
All steering designs may be manual or power-assisted. With a power steering system, engine power is used to turn a pump that applies additional pressure on the steering gear in whatever direction you turn the wheel. The first general market power steering system was introduced on the Chrysler Imperial sedan in 1951, and by the end of the 1950s was standard on most American cars. Foreign automakers came to power steering much later. Like steering boxes, power steering pumps are generally replaced or professionally rebuilt.
Apart from these main mechanical components, there are several steering components that you can and should replace. Chief among these are the tie rod ends and ball joints. Ball joints are used in place of king pins in later cars. They are ball-and-socket joints that allow freedom of rotation to your steering spindles and hubs. They generally come pre-lubricated with a rubber boot over the socket. If the rubber boot is torn, a ball joint won’t last long.
Similarly, tie rod ends connect your steering rods to the steering arm on your spindle/hub assembly. They also use a ball-and-socket joint to allow the steering system to reorient itself freely as your suspension moves through its arc.
As you reassemble, be sure to always use new ball joints and tie rod ends. You’ll be surprised at the difference they make to your car’s driving habits. Also, you’ll notice that tie rods come in left-hand and right-hand threads. This is so that your steering rods will function like a turnbuckle. Rotate the rod in one direction and it gets longer. Reverse the rotation and it gets shorter. This allows you to adjust your wheel alignment without removing one end of the rod.
It’s not obvious, but you can center your car’s steering wheel by lengthening one steering rod and shortening the other by the same amount. If you keep the wheels pointing straight ahead, this will have the effect of moving your car’s steering rack or pitman arm and rotating the steering wheel. When you take your car to be aligned, be sure to ask the technician to straighten up the wheel -they don’t always do that, and it’s part of the “new car” mystique.
Another factor to mention to the alignment technician is if you are using tires of a different design than the manufacturer specified. Most often, this will be a change from bias ply to radial design tires. Your alignment technician may recommend a slight change to alignment specifications for a different tire design.
For a classic restoration, you will always want to replicate the manufacturer’s recommended camber, caster and toe settings. These are designed to provide the best experience in standard road driving. Playing with these settings is used only in high-performance applications, and tends to trade off low-speed driveability and tire wear for better performance.