Taking the time to understand how shocks work and why they need to be changed
When should vehicle owners change the shocks on their vehicles? This is a question that often brings about a great deal of debate, both amongst technicians and consumers.
For some, automotive shocks should be changed regularly. They are wear items like any other mechanical component on a vehicle. Age and road conditions will wear a shock’s mechanics as time and use eventually wear brake friction. Others say unless a shock shows signs of damage or it has failed, it does not need to be replaced.
Bill Dennie, director, ride control channel management with Tenneco, says the often quoted rule that shocks should be changed at 80,000 kilometers is a good rule to follow, especially if one understands what happens to a shock over time.
The first thing to remember is that an automotive shock contains hydraulic fluid which over the course of a shock’s life will lose its viscosity. Dennie likens it to how motor oil wears over time. As motor oil goes through an engine it will lose its ability to provide the viscosity and protection needed to protect critical engine parts. In a shock that reaches 80,000 kilometers, “it will have gone up and down 50 million times.”
“For every mile down a road a vehicle travels, a shock absorber will work about 1,700 to 1,800 cycles per that mile. That oil inside the shock over that time will have gone through a lot of heat, so [at 80,000 km] it has lost its viscosity and it will not give you the same kind of ride as when the oil was brand new in a brand new shock.”
Along with the oil degrading over 80,000 km, the internal components — such as the base assemblies, pistons and valves, for example — will wear and their tensile strength will degrade. When that happens, the oil inside the shocks will run through the system more freely and “you don’t get the same control as you had when the shocks were brand new,” Dennie adds.
Dennie continues that what a vehicle owner often does not understand is that worn shocks can impact the handling of the vehicle, preventing the wheels from making constant contact with the road.
“For the driver, the danger is loss of vehicle control in an accident avoidance maneuver,” says Ted Wittman, a Gabriel Answerman, engineering service, with Ride Control LLC, makers of Gabriel automotive shocks. “The driver rarely tests the vehicle’s ultimate limits, and unfortunately, when they do, it is usually an emergency. This is a bad time to find out that the vehicle is not in condition to respond. For the vehicle, the danger is accelerated wear on other suspension components and tires.”
“One worn shock absorber going down a highway at 60 miles an hour, and if you have a panic stop — that one bad shock absorber or strut could increase your stopping distance by up to several feet,” Dennie adds.
Because shocks wear gradually, it is often hard to tell at first that there might be a problem. People become used to the softer ride and compensate for how the vehicle handles. Even technicians can miss the subtle clues. Sometimes the only way to tell there is a problem is to take the car out for a test drive and see what is happening, such as if the vehicle is nose-diving when the brakes are applied or leaning when taking a curve. Tenneco this year expanded its popular Monroe Ride & Drive program to include 45 visits to locations in Canada and the United States demonstrating for technicians how to diagnose ride control issues and to use that experience to educate the consumers on ride control.
A good rule to follow for technicians when dealing with shocks and ride control is that every time the vehicle comes in for an inspection or for such services as an oil change or switching out summer and winter tires, that technician should take the time to inspect the ride control to see if the shocks are showing any problems. One should remember that shocks take a lot of abuse which can sometimes cause premature failure. Things such as extreme cold and heat, poor road conditions or dusty off-road conditions can cause a shock and ride control system to fail before the recommended change interval.
Even air suspension systems can suffer from wear and premature failure, which might not seem obvious as air suspension systems seem so different from traditional shocks.
“One of the first symptoms of a faulty air suspension system is when the air suspension compressor dies,” says Todd Nash, senior vice-president of sales and marketing with Arnott Inc. “This is normally due to a small leak in one or more of the vehicle’s air springs which was undetected. Unfortunately, the compressor needs to be replaced before the actual problem can be diagnosed. Once the compressor is working again, users can spray their air springs and system with a solution of soap and water, and look for bubbles to determine if there is a leak. Typically, air springs can last 80,000 to 100,000 miles … and when they go bad you can’t just keep riding on them.
“While rubber air springs can be affected by expanding and contracting in very cold climates, the major issue with air suspension wear is often poor driving conditions, such as rough roads or if drivers take their vehicle off road,” adds Nash. “Road debris and the placement of the air strut can also be an issue. Arnott has added aluminum ‘cans’ over some of our products to protect the rubber air spring from such debris.”
“A tire rotation or a tire replacement offers a great opportunity to begin the discussion,” says Wittman. “When a customer is buying tires, they make an investment in a vehicle and are likely planning to keep the vehicle for an extended period. This is the perfect opportunity to make the customer aware of how they can protect their investment in the tires by installing new ride control as well as the usual tire rotation and inflation recommendation. Other opportunities are whenever any front end components are being replaced.”
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