I’ve replaced thousands of shocks and struts in my career as an auto technician, so I’ve definitely seen it all.

A customer once complained about the sound of a bell ringing and sloppy steering, especially on turns. During a road test, I heard and felt the same things. During a visual inspection, I found the top covers of both front shocks had rusted! They clanged against and scored the shocks’ pistons, causing all the oil to leak out. Four new shocks later, the car drove and felt like new.

Shock absorbers are often overlooked. They keep our teeth from rattling while driving, of course, but also serve a much more important purpose. Driving with bad shocks can be dangerous and adversely affect driving stability, tire wear and braking. Here’s what you need to know.

How Long Do Shocks Last?

It depends.

Unless you drive recklessly, go off-roading, drive mostly on rough, uneven or bumpy roads or do lots of hard stop-and-go driving, shock absorbers should last about 50,000 miles, or four to five years.

If you drive cautiously and mostly on level pavement, it’s not unusual for shocks to last longer than 50,000 miles. But if you live in areas that promote rust and corrosion, or in climates with extreme temperature fluctuations, it can damage your shocks’ inner seals and shorten their life.

MacPherson struts, which are similar to shocks, provide a smoother ride and absorb vibrations. They can last up to 100,000 miles. But do not confuse one with the other. Shocks and struts differ in their construction, how they function and operate.

How To Tell if Shocks Are Bad

Failed or failing shock absorbers have a “tell” — your vehicle will regularly bob up-and-down after a hard stop.

Here’s a test for your shocks: Push down hard on the bumper two or three times. Your vehicle should come to rest after one bounce. If it keeps bouncing, you hear knocking or you see fluid leaking from a shock, replace them.

Other indications your shocks need replacing include:

Longer stopping distances

Weak shocks cause the tire/wheel assembly to “hop” up and down, causing the tread to lose full contact with the pavement.

Remember, the section of tire touching the road isn’t much larger than the palm of your hand. This makes bringing your vehicle to a stop more difficult, especially at high speeds, because less friction will be generated due to less tire contact with the road surface.

Abnormal tire wear

The same tire/wheel hop can also lead to uneven tire wear. Called cupping or scalloping, that results in worn patchy sections around the outer edge of a tire.

Poor handling

Your vehicle will not ride smoothly or handle as well as the shocks wear out. Even hitting a small bump, pothole or ripple in the road can cause the steering wheel to shake, making it difficult to control the vehicle.

Strange noises

Weak, worn, broken or loose shocks and brittle or missing mounting bushings can cause sharp snapping or cracking when driving over a pothole, up a driveway incline or turning.

Mounting bushings are made from rubber, silicone or polyurethane. They act like cushions, absorbing vibrations and preventing the metal parts of the shock from rubbing against the vehicle frame or shock absorber mounting holes.

Excessive vibration

When driving over bumps or rough roads, the oil in shocks converts the vibrations into heat energy, then dissipates that energy. This reduces road vibrations. A shock with weak seals or low oil cannot dampen vibrations.

Can You Replace Shocks Yourself?

Again, it depends.

A shock absorber’s companion coil spring holds, or stores, tremendous potential energy. Think of it like a windup car. You tighten the spring until it compresses. Then as the spring unwinds, it releases that energy to propel the car across the room.

To safely remove a shock, its coil spring needs to stay compressed. Use a floor jack to lift the vehicle, then lower the suspension onto jack stands.

Some shocks are easy to reach and replace. Others aren’t, and shouldn’t be replaced by a beginner.

Check the vehicle’s service manual to locate your shocks. If you can see and reach all the nuts, bolts and other fasteners, and you have the right tools, then go for it. If the shocks are buried under other car parts, or the fasteners are rusted or missing, let your mechanic to replace the shocks.

If you decide to DIY it, you’ll need these tools:

• A 3/8-inch or 1/2-inch socket set with extensions;
• Box or combination wrenches;
• Hammer;
• Hydraulic floor jack;
• Jack stands;
• Rust penetrating oil;
• Safety glasses;
• Torque wrench;
• Wheel chocks;
• Work gloves;
• Impact wrench (optional).

Pro tip: Never overtighten fasteners when installing new shocks. You may not find a specific torque specification for the mounting bushing nuts.

Only tighten hardware until the outside diameter of the bushing lines up with the outside edge of the mounting washer. Tightening the nut until the bushing flattens or squeezes out past the mounting washer reduces a shock’s ability to absorb road bumps and reduce vibrations.

Cost Estimate To Have a Pro Replace Shocks

The cost depends on labor costs where you live, year, make and model, plus the quality of the shocks and the difficulty to remove and replace them.

Virtually every car on the road has only one shock per wheel, or two per axle. Always replace shocks on the same axle (front or rear) in pairs at the same time. Labor can run from $100 to $300 per axle.

Expect to pay $50 per axle for a basic or conventional shocks, or $100 to $300 for per axle for shocks that offer improved load capacity or handling, such as:

• Heavy-duty;
• Air-adjustable;
• Coilover (not to be confused with a MacPherson strut);
• Gas-filled;
• Adjustable, which controls how a vehicle rides and handles.

Before you buy anything, do your research. Replacement shocks should meet your driving needs. If your shocks are simply worn out and you liked the way your car drove when it was new, then install the same type of shock.