by Jim Kerr

I was driving to work the other day on my normal route over the freeway when I crossed over some expansion joints on an overpass. My truck gave a slight jump as I crossed the angled joint and I suddenly realised that my truck was soon due for new shock absorbers. It wasn’t bad yet but the telltale signs were there.

Most people don’t realise their vehicle needs new shocks until they get much worse. The wear is usually so gradual that we become accustomed to how our vehicle drives and take it for normal. Every now and then I see another vehicle on my travels that is slowly floating up and down as it travels down the smooth highway. The driver seems totally unaware of the vehicle’s motion but this vehicle has badly worn shocks.

Struts (MacPherson Struts), used on many cars are a larger version of a shock absorber. Struts have a shaft in them about the diameter of a large thumb because the strut has the job of holding the suspension upright. Shock absorbers have a shaft about the size of your little finger and are only used to control suspension movement. Struts can wear the same as shocks but usually last longer because of their larger surface areas on the shaft and internal parts to accommodate the wear.

So how do you know when it is time to replace your shocks or struts? Let the handling of the vehicle tell you. The typical test is to push down with all your body weight on one corner of your vehicle at a time and quickly jump off. The vehicle should rise, go down slightly and then return to its normal height. If the vehicle bounces more than this, then the shock or strut is worn. The trouble with this test is it only checks for severely worn units.

Most of our driving is done on relatively smooth road surfaces. The suspension is moving up and down only a small amount so all the wear in a shock or strut is concentrated in that small area. Hit a bigger bump and the shock moves to an unworn part of its travel and seems to work fairly well. It is the smaller bumps that need improved control. To check for wear in this small range of travel, you have to become aware of your vehicle’s handling.

Because I test drive many new vehicles, I am used to the feeling of good shock control. Worn shocks become much more obvious. If you are driving the same vehicle every day, then you need to take a critical assessment of your vehicle’s ride and handling over small bumps to determine how good your shocks are working. If your vehicle skitters a little bit or gives an extra little bounce when hitting a small bump, then you are soon ready for new shocks.

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