Over the past few months, since we launched the “Ask The Expert” feature, we have received many shock absorber related questions. These vary from “how often should I replace my shock absorbers” to “can I rebuild a strut” or “must I replace all four shocks together”.

This week, we look at some of these and other frequently asked questions regarding shock absorbers. The information below has been supplied by KYB .

KYB is one of the world’s foremost shock absorber manufacturers; it is the largest OE shock absorber supplier in Europe and KYB shocks can be found in 1 of every 4 passengers vehicles manufactured worldwide.

Start My Car is proud to be a distributer of KYB suspension products. If, after reading the questions and answers below, you realise you need new shock absorbers – head over to our website to browse our extensive range of KYB products. And in the event you don’t find your product online, reach out to us and we will do our best to order it for you.

1. What causes my vehicle to make clunking noises even though my shocks/ struts are new?

This is usually caused by a mounting problem and not the shock or strut itself. Check the components that attach the shock or strut to the vehicle. The mount itself may be worn enough to cause the shock/strut to move up and down. Another common cause of noise is that the shock or strut mountings may not be tight enough causing the unit to have some slight movement between the bolt and bushing or other attaching parts.

2. Can I compress my shock/strut too easily by hand. Does this mean the shock/strut is weak or defective?

You cannot judge the strength or condition of a shock/strut by hand movement alone. The force and speed generated by a vehicle in operation exceeds what you can accomplish by hand. The fluid valves are calibrated to operate differently depending on the degree of movement inertia which cannot be duplicated by hand.

3. When do I need to replace worn shocks or struts?

There are four main reasons that determine when to replace them:

• To restore the vehicle’s designed performance (usually after 80,000 Km);
• when the vehicle has excessive ride control conditions (i.e. nosedive, body roll, etc.);
• when the vehicle has a failed unit (i.e. dripping hydraulic fluid, tyre cupping, excessive bounce, etc.); or
• to upgrade performance

4. Should I consider replacing any other part while having my struts serviced?

Yes, it is also a good idea to replace both the strut mount and the protection kit when replacing struts.  The strut mount optimizes suspension performance by providing a smooth steering response and reducing vibration. Protection kits will protect your new struts from dirt, dust, salt and leakage.

5. How do I know if a strut is rebuild-able?

Struts cannot be refilled or rebuilt. However, some struts have a replaceable cartridge. These repairable struts can be identified by a large hexagonal shaped nut at the top of the strut body. Please remember that struts are usually gas charged and that replacement should only be performed by a qualified technician.

6. Do I need to align my tyres after I have my struts replaced?

It depends on the vehicle design. A strut by design is also a component that supports the wheel & tyre. Some models aren’t affected when the struts are replaced while others do change the wheel alignment. Strut removal & installation potentially changes the position of the tyre alignment. Some struts have adjustment slots to perform the alignment with. All struts affect alignment in some way so it’s best to check the specific vehicle service manual and specifications.

7. What is the difference between a monotube and a twin-tube design?

By far, most vehicles (cars & trucks) in the world come factory-equipped with a twin-tube style shock or strut; probably 85% or more. The twin-tube is cost-effective and performs very well when the vehicle is operated within its designed purpose and for average, everyday use. In many other model vehicles, when the manufacturer designs a vehicle for more than average driving conditions, they often choose a monotube style shock. It’s a bit more costly, but has a quicker response rate, has no performance fade due to aeration and can automatically add performance just when needed. For vehicles factory-equipped with twin-tubes, the monotube replacement shock absorber becomes a performance upgrade opportunity. It can increase a vehicles handling and stability without dramatically decreasing ride comfort.

8. Can worn shocks or struts cause my new tires to wear unevenly?

Absolutely. Shocks and struts provide damping force to control tire movement. When the tires move excessively, they develop a “cupping” wear pattern that damages the tyre. Other factors such as incorrect air pressure, worn suspension components or improperly aligned steering also causes uneven tyre wear.

9. If I have a twin-tube shock can I switch to a monotube shock?

Yes; for many vehicles that come factory-equipped with a twin-tube, KYB offers a monotube (Gas-a-Just) as a performance upgrade. This will increase the vehicle’s handling and stability beyond the factory design. Please use the KYB catalogue to see if there is a monotube available for your specific vehicle.

10. What is the difference between original equipment KYB and the aftermarket KYB components?

Original equipment KYB shock and struts are designed to the OE manufacturer’s specifications. Although built on the same assembly lines, the aftermarket KYB products are calibrated to compensate for worn suspension components to help restore the vehicle’s original handling and control characteristics. KYB aftermarket also offers monotube shocks which for most vehicles will provide additional control and handling capabilities.

11. I noticed a light film of oil on the shaft of my shock/strut do I need to replace them?

Probably not; a small amount of oil is normal and is used to lubricate the polished shaft and the upper seals. However if the unit is extremely wet or dripping oil, the unit should be inspected by a qualified technician.

12. Why do I need to replace worn shocks or struts?

In a nutshell: To keep the vehicle’s stability within its designed capability. Stability means keeping the body as level as possible during bumps, turns and stops, while keeping the tyres on the road under all conditions. The shock’s main function is to resist body & tyre movement, but as shocks wear the vehicle becomes unstable; the steering feels less responsive, the body leans more and the tyres grip less. Stopping ability can be reduced as much as 23% and the driver needs more skill to keep the vehicle on the intended path and from losing control on curves. Shocks cycle about 1000 times per Km driven. After 80,000 Km, that’s 80 million cycles. Because shocks use metal discs that flex with each movement, they become fatigued over time which causes the reduced performance, which is why replacement shocks and struts are suggested after 80,000 kilometres.

13. What is the difference between shock absorbers and struts?

The function is essentially the same, but the largest difference is the way they mount to the vehicle. The strut design acts an integral part of the suspension by replacing the upper control arm and acting as a pivot point for the steering. The shock design is used in addition to the suspension and steering components.

14. Do the strut mounts come with the bearings?

Many do, but only when the strut mount is also the steering pivot. The bearing is a wear item and affects the steering response as well as wheel alignment.

 15. Why should replacement spring always be fitted in axle pairs?

Although one spring may have broken and requires replacing, the other springs will be fatigued, and failure may be imminent. As with shock absorbers, replacing just one spring will result in an unbalanced axle which will manifest itself with uneven braking and handling.

16. What kind of controls do KYB use during production?

Everything is controlled concerning both quality and tuning parameters. For quality, KYB tests design specification, component quality, production line quality. For tuning parameters, KYB tests piston orifices, initial load of valves and springs, thickness and quantity of valves, piston ports, nut torque settings.

17. Why do I need to check suspension geometry after fitting new springs?

As springs fatigue and sag, caster, camber, toe and the turning circle are affected, therefore, a full geometry check after fitting new springs will reduce wear in tyres, track rod ends etc.

18. How do I adjust a Gas-a-Just shock absorber?

The name of this product refers to an internal self-adjusting valve mechanism. It is not possible to manually adjust this shock absorber.

19. Why are coil springs which come off a vehicle often longer than the new springs supplied as replacements?

Because the old springs have become coil bound. They have stopped returning to their original height following extensive compression.

20. Why are shocks for OE and aftermarket sometimes different?

Because OE shocks are designed according to manufacturer specifications for a brand-new vehicle. For the aftermarket, the shocks are designed to compensate for the fact that other components on the vehicle are likely to be worn and KYB wants to restore the way the suspension performs to how the manufacturer intended. The main differences are the damping force and the stroke length.