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Restoring a Classic Suspension

Dealing with the nitty-gritty

In the last article (Keeping You In Suspension) we discussed how to improve the deteriorating handling characteristics of an aging car. Let's start out by summing up what the repairs and restoration may involve.

As the car is probably more than 20 years old, and well used, just about all of the suspension items that can wear out probably have worn out. This will entail replacing all of the bushings, ball joints, tie rods, springs, and shock absorbers along with any other wear item that you may find in the process. The handling can also be improved with the addition of sway bars, if the car never had them, or by upgrading the bars that the car already has.

Count on replacing all of these items at the same time. This will make your life easier in that the various components will not have to be disassembled numerous times. In many cases, the entire suspension can be removed as a unit, rather than as individual parts. This will allow many of the components to be rebuilt and restored on a workbench instead of underneath the car.

Spring Compressor

Now let's get down to the nitty-gritty details of replacing those greasy parts and pieces. There are a few special tools that you will need to have. The most important is a spring compressor. This will allow you to compress the springs of the car so that they can be removed without hurting yourself. A good set can be purchased for about $50. There are a few different kinds available, so make sure you know what you need before you buy them.

Various types of press tools may also be needed depending on the style of bushings and ball joints your car has. Buy a manual specific to your car to make sure.

In the photos shown here, the vehicle used as an example of a suspension resto is a 1972 Porsche 914. The front suspension is a MacPherson strut design with a torsion bar rather than a traditional spring. The spring action is produced by twisting a straight bar along its length rather than compressing a coiled spring. This system is very simple and compact, a great starting point for any project.

Coil-Over Shock

The rear suspension has semi-trailing arms with coil-over springs. The main suspension arm in this system pivots at a slight angle to the length of the car, thus "semi-trailing" as opposed to "trailing." The "coil-over" refers to the fact that the spring coils up around the outside of shock absorber. This also is a fairly simple design.

After the suspension parts have been removed and cleaned, make sure to give everything a very close look. Items that generally do not wear can sometimes be damaged. Check the suspension arms for small cracks around the bushings and other mounting points.

If you find a crack, stop. It has cracked because of the extreme stress and age. The flexing that it has endured over the years has weakened it until it is dangerously unusable. Do not attempt to weld these cracked arms. All of the metal is weak, but it is just showing up at the crack. You will need to buy a new one or find a good used replacement. Remember, if you do find a crack, then this is your cue to look extra carefully at the rest of the system for similar wear.

Bushings into Frame

The bushings in our 914 are easily replaceable. They merely push right on out with a small amount of force. Sometimes, if they are dirty enough, they may need a few taps with a hammer and punch. Other cars have bushings that are pressed into place with a hydraulic press. Even if you have a press, you will have to make special braces to support the arm. If you try to press the bushings in or out without the proper brace, you will bend the arm. Fortunately, many automotive machine shops are already set up to do this very job.

The ball joints are usually located on the outer ends of the suspension arms. The Porsche only has a ball joint in the front, one per side. It is easy enough to remove as there is only one large nut holding it in place, but you will need a special tool to get at the nut.

Of course, the methods for holding the ball joints in place can vary. Some use rivets that can be drilled out and replaced with bolts, others are pressed into place. Make sure you know your application. If your steering has been feeling loose, then the tie rod joints could be the culprits. The tie rod is essentially a ball joint in another application. They are the final link from the steering to the wheels.

Ball Joints

Once again the Porsche uses an unusual wrench to remove and install these parts. Replacing just about any suspension part can affect the alignment of the car's wheels, but when you replace the tie rods, very large changes can be made with just a tiny adjustment. It is imperative that the car be aligned at a competent alignment shop after this work is done. It may even be safest to have the car towed to the shop, as it will be difficult to determine just how far off the alignment really is just by looking at it.

Springs and shocks are often replaced as a unit. The front shocks on the Porsche are replaced as a cartridge. The old shock insert is pulled out of a tube, and the new one is slipped into its place. Real simple. The rear is a little more complicated, as the springs attach around the outside of the shock.

The replacement shocks used in this project are Bilstein. Fortunately, this shock design features an adjustable spring mount. By moving the mount, the ride height is adjustable, without having to change the stiffness of the springs.

Adjustable Spring

You will need to use the spring compressor to remove or install a spring on this type of system. Remember that these springs hold the entire weight of the car. Never point the springs at yourself or anything that you care about while they are being held in the compressor! If the compressor slips off, the spring and compressor will fly with great force. Make sure that you pay close attention to where all of the washers and nuts go as you disassemble the upper spring mounts. You will probably be using most of these over again on the new shock and spring unit.

Regarding sway bars, entire books could be written on the proper selection and use of sway bars. Without going into detail, try to avoid extremes. Don't install the biggest, stiffest bar available, but at the same time it is wise to avoid small and weak ones that will not make a noticeable change in the cars handling.

Although Porsche had a sway bar available for the front and rear of the 914 model, this particular car had neither.

Front Sway Bar

The front bar is unique in that it goes through the body of the car, near the fuel tank. Thus, the tank has to be removed to install it properly. A fair amount of precision drilling and cutting needs to be done on this installation. With time and patience, a skilled novice could do a fine job in installing it. Make sure that you feel up to this kind of task and that you know what you are getting into before you start. Make sure that your kit comes with instructions!

The rear sway bar is a little more traditional. It attaches to the inside ends of the trailing arm and then attaches to the underside of the frame. Installation methods will vary dramatically, so we will not go into great detail on every bolt. The only real change to the suspension involves the lower rear shock's mounting bolts being replaced with ones that have a mounting hole for the sway bar links.

Rear Sway Bar

The most important things are to make sure that everything is put in straight. The sway bar should not be at an angle to the vehicle. There should be equal distances from the sway bar to the suspension arms on both sides. Another very important factor is that the mounting point of the sway bar on the frame should be determined with the full weight of the vehicle on the ground. This way, the suspension is compressed to about the height that it would be during regular driving.

Following these general rules will make the installation easier, and its function should be greatly improved once the car is back on the road. There are so many parts that can seriously wear out on a suspension system that replacing them can make all the difference in the world. A car that feels clumsy and unstable can turn into a thoroughbred with the proper care. Take time and patience in all of this work and you will be rewarded with an older car that handles as good as or better than new.