The life of shocks and struts depend on the road conditions the vehicle drives on, the weight of the vehicle and environmental conditions. Some vehicles; such as SUVs and Vans, are very heavy in the front and can wear out suspension components in 50,000 t0 75,000 miles. Vehicles driven in northern climates will wear out quickly due to road salt and potholes created from icy conditions. Delivery vehicles carrying heavy loads will wear out springs and suspension components quickly.
So, mileage is not always the best way to estimate how long your shocks and struts will last. Consider the type of vehicle, your normal road conditions, load, and towing frequency and the climate conditions.
Suspension parts should be inspected every 12,000 miles for the following conditions:
Bent, rusted or broken components such as spring seats, brake, and ABS brackets, strut mounts and springs.
A test drive should check for nose dive, sway and excessive bouncing of the tires
Strut mount noise when turning the steering wheel right and left
Measuring from the ground to the top of the fender well on all four tires to see if there is a variation in ride height of more than ½ inch.
Damaged or missing dust bellows or bump stops on the piston rod shaft
Clear oil residue on the shock absorber tube leading to the top oil seal
The main cause of oil and gas leaks is a failure of the seal. The piston rod moves back and forth through the seal; if the piston rod is dirty or damaged with a small scratch or pit, the seal can allow oil and gas to leak. When replacing shocks and struts; always make sure the dust bellows and bump stop are replaced as well. Do not leave the piston rod exposed to dirt and gravel damage or the part will fail prematurely.
Inert gas is added to the shocks/struts to prevent the oil in the part from foaming. As the piston moves up and down in the shock oil; heat is created and the oil may develop bubbles that reduce the performance of the part. Gas pressure prevents the oil from foaming and reducing dampening performance of the part. This is like a carbonated drink that is shaken, the contents are okay until the cap is removed and the pressure escapes.
Suspension systems that use shock absorbers generally are not affected when the shock absorbers are replaced. We recommend alignments anytime replacement struts are installed.
Can shock absorbers be mounted upside down and still work?
Most shock absorbers are a twin tube design. Mounting the shock absorber at an angle greater than 45 degrees may allow gas to enter the inner chamber with a result of poor dampening performance. For this reason, always prime or test shock absorbers and struts with the piston rod up; do not turn the part upside down with the piston rod on the ground to test dampening.
There are specially designed twin tube shock absorbers that use a gas cell to retain gas in the outer reserve tube that can be mounted upside down or exceeding a 45-degree angle.
Both shock absorbers and struts are used to control wheel motion up and down to maintain control of the vehicle and improve the vehicle ride. Struts are incorporated into the suspension system to hold the spring and act as a pivot point for turning the wheels.
The primary purpose of shock absorbers and struts are to maintain the tires in contact with the road surface. If there were no shock absorbers or struts; the wheels would bounce constantly off the road surface. When the tire is not on the road surface; the driver does not have control of the vehicle.
The secondary purpose is to improve the ride of the vehicle for the driver and passengers. This is where the ride control science dampens the movement of the tires and helps remove vibration.
Tires will wear out prematurely, the vehicle becomes more difficult to stop, steer and maintain tire contact with the road. The vehicle will be difficult to control and unpleasant to drive. The ability of the driver to make emergency maneuvers and stops is compromised.
Prior to starting the install; measure the ride height at every tire. Using a measuring tape; measure from the ground, across the center of the wheel hub to the bottom of the fender. Record the measurements for comparison after the install.
Use this opportunity to do a full inspection of all suspension components. Check the sway bar links and sway bar assembly bushings for cracks or tears. Check the upper and lower control arm bushings to make sure the rubber components are not cracked.
After the old part is removed; lay it beside the new part. Compare the length, bracket positions and strut mount designs to verify the replacement part is compatible with the old part.
For struts, install the top first, then install the bottom. Remember the strut mount assembly includes a bearing that allows the strut to rotate to the correct mounting position.
If a bare strut is being installed; the strut mount should be replaced if there is corrosion or damaged rubber. Make sure a new dust bellows and bump stops are installed.
After installation, measure the ride height again. Remember; if complete strut assemblies were installed, the ride height will increase by about 1 inch. The old springs will have sagged. If shock absorbers are installed, remember the shock absorber does not have any impact on ride height. Raising the vehicle off the ground to install the shock absorbers will result in the original springs riding a little higher for 50 to 100 miles. If the vehicle has lower control arm bushings with corrosion; sometimes the metal bushings will twist the rubber and cause the vehicle to ride higher. Generally, this will settle down within 100 miles. If the vehicle does not settle down to within 1 inch, you may need to loosen and tighten the control arm bushing nuts with the vehicle load on the control arm.
The complete strut assembly includes a new spring, strut mount, dust bellows, and bump stop. It is about 50% faster and much safer to install a complete strut assembly compared to a bare strut. Generally, a new strut mount, dust bellows, and bumper are needed with the bare strut replacement. So, the complete strut assembly saves time, is cheaper than the bare strut plus purchasing the replacement strut mount kit and is much safer to install.
Remember, the strut mount assembly includes a bearing. This allows the strut to move right and left as the steering wheel is turned. If there is one-part number for both sides of the vehicle, the strut mount may need to be turned when installing on one side. Install the strut mount end of the strut assembly first. After the top is secure; turn the strut mount assembly to the correct position to mount the bottom using a long screwdriver in the bracket holes or by hand. The strut may be difficult to turn with some bearing designs.