Sunday, November 18, 2018 Detailed Auto Topics
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October brings cooler weather and for some repair shops, a slow down in business. The heat that drives many repairs is going, and sales opportunities with them. Part suppliers also feel the pinch and offer incentives to repair shops that push their products in the fall.

Why shocks and struts

Shocks and struts are high profit items and are often over recommended. This is easy because marketing has convinced many drivers they will need struts and shocks. The truth is original equipment components are very good, and seldom fail before 100,000 miles. Original equipment struts and shocks sometimes last the life of the vehicle. Worse, aftermarket component may not be as good as the original part replaced.

What is the difference in a shock and a strut?

They sometimes interchange the term shocks and struts. Technically they are different, but from the driver’s perspective they serve the same function. Both dampen motion of the vehicle and help keep the tires in contact with the road.

Excess jounce or rebound is a reason for replacement

As a tire rolls over a hump in the road, the spring compresses and then pushes the body up. Inertia keeps it moving up, until vehicle weight and the suspension of the vehicle pulls it down. Upward travel we call jounce and downward we call rebound.

The springs in the suspension would continue to oscillate if not controlled by the shock absorber. Shock absorbers and struts resist motion and keep the vehicle from bouncing.

Shocktober

Common sense dictates about the same number of shocks and struts will need replacement in any month. Why would far more struts or shocks fail in October? The answer is they do not. Marketing suggests we should buy in October. For instance a buy three, get one free offer, is not a good deal, if we do not need the product at all.

Beware of recommendations that coincide with sales

Shocktober sales work because marketing convinces folks they will need struts and shocks eventually. When they see a supposed discount, many feel they will take advantage of something they will need anyway. The parts installed may not be as good as the parts replaced. A 25% discount, on a part that is inferior to the original, is no bargain.

Bogus reasons why they recommend shocks and struts

Some oil around the shaft is okay

Leakage - Oil on the housing of the shock or strut does NOT mean it is bad. Some wetness around the shaft is considered normal, and is from oil that lubricates the seal. A shock or strut that is wet and has oil dripping does suggest a problem.

Time or miles - Struts and shocks do NOT have a recommended time or mileage interval. Replacement is a repair and not a maintenance item. Some shocks and struts last the life of the vehicle.

Tire wear - Most cupping and irregular wear on tires is due to misalignment or out of round tires, not worn shocks or struts. Be skeptical of recommendations based on tire wear.

Noise - Struts and shocks can cause a bumping noise, but so can their attachments and many other components. Finding and correcting suspension noise requires a proper diagnosis.

A sale or special - Be very wary of part failure that coincides with a sale. Shops often receive incentives to push products that are on sale. If they can make money at the sale price, why do they charge more when not on sale?

Symptoms of bad struts and shock absorbers

The leading symptom of worn shocks and struts is excessive bouncing after hitting a bump and a floating feel when driving. Shocks and struts dampen jounce and rebound, after a tire strikes a hole or hump. They may also cause a dip or dive on braking.

Jouncing suspension to check shocks

Traditionally, people have jounced the suspension and watched for the number of cycles, to check shocks and struts. More than one or two cycles indicates a worn part. This method reveals only a very worn-out shock or one that is seized. Because modern dampers use multi-valving, this method is not accurate enough to detect wear. Some shops measure temperature change to judge a shock absorber more accurately. Driving on a rough road causes a good shock or strut to develop heat. This can be measured and used to determine how well the shock works. Test-driving the vehicle and watching the response to dips and bumps also works.

Another cause for replacement is internal noise that they have diagnosed, as caused by the strut or shock. A question to ask is, "Is it guaranteed this will correct the problem?" If the answer is anything but yes, get a second opinion.

A broken mount requires replacement

A shock or strut that is physically broken is obviously in need of replacement. This is rare on original equipment parts.

A trusted mechanic should inspect struts and shocks we suspect need replacement. True professionals explain why we need items they recommend.

 





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