Auto Service World
Feature   June 1, 2003   by Dean Askin

Shocking Safety

Control, comfort, stopping power are all linked to well-performing ride control

The shock absorber. The strut. They’re not just a component for ride comfort anymore. Developments in tires, independent suspension and MacPherson struts, combined with the changing types of vehicles on the road, has elevated ride control to a critical role in ride control and vehicle safety. But shocks aren’t getting the attention they warrant from vehicle owners, technicians and shops alike.

“The importance of dampers and how they control the spring and vehicle cannot be understated,” says Tom Hannon, Director of Marketing, ArvinMeritor Light Vehicle Aftermarket. “The words ‘shock absorber’ can be misleading, for they do much more than just make the ride comfortable. Perhaps we should have called them safety enhancers.”

Shocks cushion the vehicle ride, keep the wheels in alignment and support the vehicle’s weight, but their key role is keeping tires in contact with the road. Worn units compromise that tire/road contact, along with braking power and overall control and safety.

“In most of today’s vehicles, worn shocks and struts can adversely affect both ride control in general and braking specifically. The vehicle will have less ability to maintain control and will take longer to stop under many conditions,” says Hannon.

According to statistics from The Cologne Institute, a vehicle moving at 50 mph on four shocks performing at 100 per cent needs 104.8 feet to come to a complete stop. The same car would need 117.1 feet to stop if one shock is at 50 per cent performance – a difference of 12.3 feet.

That’s similar to the results of testing done for Monroe and certified by the United States Auto Club. Twelve different vehicles, including a Dodge RAM Truck, Ford Explorer, Chrysler minivan, Ford Contour, Chevy Tahoe, BMW and Toyota Camry were tested on a dry, bumpy surface. The tests compared stopping power between vehicles equipped with four new Monroe Sensa-Trac shocks, and three new and one 50 per cent-degraded OE shock. On average, 60-to-0 mph stopping distance increased 10 feet for vehicles equipped with a worn shock.

Mark Christiaanse, Director of Product Management for Ride Control at Monroe, says he’s “surprised that some technicians have never made the connection” between ride comfort, tire/ road contact and stopping power.

“There was too much emphasis in the past of thinking that shocks were comfort and not enough really that in the course of that comfort, they’re also keeping the tires on the road and the link from tires on the road to ‘hey, that could probably help me stop better.'”

Chuck Gonwa, Marketing Manager for shock manufacturer KYB, says drivers, technicians and shops don’t pay enough attention to shock wear and the safety aspect because shocks are a component that wear gradually over time.

“It’s not like brakes or exhaust – when they’re gone, you know it. Shocks wear gradually and people become accustomed to the ride. Plus, some vehicles have very soft rides to begin with and as it deteriorates, you really don’t notice it,” he says.

How often should shocks be inspected? That depends on who you ask; the opinions differ. KYB’s Gonwa firmly believes shocks should be inspected “every time a vehicle is up on the rack for any kind of work.” Hannon of ArvinMeritor, which manufactures the Gabriel brand, says shocks and struts should be inspected “at least annually.” Monroe’s Christiaanse advocates a shock inspection every 70,000 km.

Oil stains, signs of rust, loose mounts, dust boot condition, bushing deterioration, dented housings, and paint finish condition are all key things that technicians should be watching for. “A complete inspection can take about five minutes. It’s not very difficult, as long as you know what you’re looking for,” says Gonwa.

The old “bounce” test – pressing down on the corner of the trunk and watching the vehicle’s reaction – doesn’t necessarily do the trick anymore. While Gonwa believes the test is “still valid,” Christiaanse doesn’t encourage it because MacPherson struts and independent suspension “Have really changed the way a vehicle is going to respond to the bounce test. In a lot of cases, you can’t push the corner of the vehicle down enough.”

All agree a test drive is the best test of shock absorber performance for control and safety. “That’s difficult to do in some cases because they’re not going to be able to spend that much time with everyone,” Christiaanse acknowledges.

Monroe is trying to educate and encourage shops and technicians to inspect what it calls the “Safety Triangle” that includes interdependent components – tires, brakes, shocks and struts – that help determine a vehicle’s steering, stopping and stability characteristics. It’s in the midst of the Monroe Ride Safe Tour, an interactive exhibit featuring vehicle simulators that show how components interact and what can happen when one fails. The Tour, which began in March and ends in October, stops in 35 cities across the U.S. and Canada including Vancouver (May 21/22), Toronto (September 22/23) and Montreal (September 29/30).

If you do an inspection and find a worn shock, how many do you replace to maintain vehicle safety and control stability? Gonwa says the number of shocks replaced is often determined by the customer, who may not be able to afford an expensive shock absorber job on top of other repairs.

“In a perfect world, I’d recommend all four because the vehicle is balanced on all four corners and sometimes you can get pitch front to rear. But at very minimum, they need to be replaced in pairs,” says Christiaanse.

From an engineering view, says Christiaanse, shock design hasn’t changed all that much in the past 20 years. The basic shock still does what it’s supposed to do – convert kinetic energy into heat energy and dissipate it with piston rod movement through oil. It’s the features of today’s shocks that have changed a lot. There are adjustable shocks; automatically adjustable sensing shocks – shocks that adjust with automatic response to the road; multi-position, manually adjustable shocks for off-road vehicles and performance cars.

Standard shocks do the basic job, but it’s premium shocks that can enhance vehicle safety, says Christiaanse. “Premium ones add added technology that actually make it a little bit better as far as safety goes,” he says.

And added safety is critical today, especially with the proliferation of SUVs on the roads.

“It’s very, very critical today for the bigger vehicle,” says Gonwa. “It’s obviously a weight disadvantage, safety wise, for people in smaller vehicles so it’s important that people are able to control these big monsters out on the road.”

The challenge for the ride control industry is convincing shops and technicians to rethink shock absorbers. “They should be looked at as a critical safety component, not just as a vehicle component that is replaced when worn,” says Hannon. “But, the reality is that they are not looked at that way and technicians can help to educate consumers about the importance of the safety aspect of shocks and struts.”

For independent shops, safety and profitability actually go hand in hand. “What we want to show them is that if you take time to inspect, and do your customer a favour and point out that you need struts, just two repair jobs a week can result in a lot of retail sales,” says Gonwa.

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