Without the shock absorber the modern automobile would simply flail about on its springs. The shock absorber is technically a damper. The shock absorber works to dampen the bounce created by bumps in the road and the weight of the vehicle acting on the suspension and springs. The less obvious yet more important benefit of shock absorbers is control. The four small patches of tire making contact with the tarmac won't do much good if the tires are spend more time bouncing in mid-air than staying planted on the ground. As anyone who has ridden in or attempted to pilot a vehicle with blown out shock absorbers can attest, brakes and steering become dangerously ineffective when shock absorbers lose their damping ability.
Bounce a superball onto hard concrete and it bounces right back. When the collective weight of that 1971 Dodge Demon pushes down onto its torsion bars and springs, the springs in turn want to push the car back up into the air like the superball. So it goes. Take that same superball and toss it into thick deep mud instead of onto hard concrete. It will stop dead. The shock absorber is the mud in the suspension. Inside the shock absorber is a cylinder full of oil, and sometimes a pressurized inert gas. The mud - such as it is. Through a series of valves the shock absorber uses this oil and gas to dampen the energy of the spring, and keep the car from bouncing about. Tires stay on the road where they belong. Vehicle control is maintained!
The valves and seals inside the shock absorbers get beat up over time and wear out. Wicked bumpy roads or over enthusiastic driving can accelerate this process. As the wear usually happens in an almost imperceptible fashion, watching for the signs of worn shock absorbers is safe thinking. The car bouncing about the road while attempting to drive is the most glaring sign of worn shock absorbers. Cupped tire wear is another sign of dead shocks. Worn shock absorbers wear out tires in cupped strips or odd patterns because the tires spend half their time in the air, and the other half smacking the pavement. Testing the shocks by giving a good downward push on a corner of the vehicle is old school test. Watch for bouncing. Four bouncing balls with a car on top of them is not the best scenario for superior handling, safe braking, or long tire life.
Strut or Shock?
Removing and replacing the shock absorbers is usually a relatively straightforward nuts-and-bolts type procedure if the springs and shock absorbers are divorced - and not integrated into what is known as a MacPherson strut assembly. The best way to find out if the shock absorbers are of the divorced spring and shock, or MacPherson variety, is to take a look either under the vehicle or in the service manual. If the spring and shock can clearly be seen as two distinct parts then Scotsmen have had no influence on your suspension. If the spring and strut and spindle is an all-in-one unit then a tool called a spring compressor is required to liberate the shock absorber or strut insert from the MacPherson strut assembly. We'll get into spring compressors, innovative and lasting Scottish suspension engineering, and strut assemblies next week.
Stuff You'll Need:
· Repair or Service Manual
· Set of Replacement Shocks
· Jack and Jack Stands
· Hand Tools
· Penetrating Oil
The bounce test is one way to figure out if the shocks have gone soft. Push down on the vehicle and release your grip. Watch to see if the body bounces around three or four times, or recovers and settles quickly. Bouncing is not good.
If you see something like this up under the car then tune in next week. This is a spring compressor on a MacPherson strut. The shock absorber is held captive by the assembly. The shock absorber works more or less the same way, but removal and replacement is more involved.
To get at the shocks first remove interior covers to access upper shock mounting nuts. Loosen and remove nut. If shock shaft spins with the nut, use pliers or a wrench on top to hold things in place.
Jack up the vehicle. Use some penetrating oil to help loosen stubborn or rusty bolts down under. Go make a sangwich, or read Jalopnik for a while. Let the oil do its work.
Remove the lower shock mounting nut and washer. Remove old shock absorber. A pry bar in between the shock mount and the shock comes in handy under extra crusty conditions.
Compare new and old shock absorber. All grommets and bushings have to go in the same spots. Note plastic strap on new shock. Don't cut or remove the strap just yet.
Mount lower end of shock first. Tighten lower mounting bolts. Line up top of shock in mount before cutting retaining strap.
Don't forget to put the grommets on top of the shock absorber where it meets the underside of the chassis. Cut the retaining strap, and guide shock into place.
Install the upper grommets and mounting nuts. Reinstall wheels. Lower vehicle. Torque down the wheel lugnuts! Jounce vehicle 3-6 times to settle the grommets and suspension. Retighten upper bolts if required. Tighten the bolts just enough to slightly compress the grommets. Think skateboard trucks.
If a locknut is supplied use two wrenches to tighten the mounting nuts against each other to lock them together. This trick also works in reverse to break loose locked nuts.
Next Week: MacPherson Struts