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High- Tech Suspension and Ride Control


5/1/2006
By Larry Carley

Unlike stock replacements, consumers buy performance shocks with a suspension upgrade in mind. In order to close the sale, you need to be savvy enough to relate to your performance customer.
 

The performance shock market includes many different segments: trucks and SUVs, sport compact cars (Honda, Dodge Neon, Mitsubishi, etc.), sports sedans (BMW, Audi, etc.), sports cars (Porsche, Corvette, Mazda Miata, etc.), street performance cars (late-model Mustang, Camaro), vintage muscle cars (older Mustang, Camaro, Dodge Chargers, etc.), hot rods ('32 Fords, etc.) and kit cars (replica Cobras and others).

Nobody knows for sure how many performance shocks and struts are sold annually in the aftermarket, but the overall replacement aftermarket for all kinds of shocks (stock and performance) is estimated to be about 22 million units a year in the U.S.

The problem with stock replacement shocks and struts is that customers don't buy them until their originals have worn out. Even then, they may not realize how much the ride control characteristics of their original equipment dampers have faded over the years. The piston seals inside shocks and struts wear as the miles accumulate, and eventually they lose the ability to maintain a leak-free seal. The valves that control compression and rebound inside a shock also wear and provide less resistance than when they were new. So the question is, at what point are the original equipment shocks and struts no longer providing adequate ride control?

At least one of the leading shock manufacturers now recommends replacing shocks and struts every 50,000 miles. Its reasoning is that the average shock loses a significant portion of its original dampening ability by the time it has experienced 50,000 miles of everyday driving. Shocks contribute to driving safety by maximizing wheel contact with the road. They also minimize body roll, which reduces the risk of rollover in SUVs with a high center of gravity.

With performance shocks, it's a different story. You don't have to wait for the original equipment units to wear out. You can make a sale at virtually any point in a vehicle's life, whether it is 20 years old or brand new off the showroom floor. People buy performance shocks when they want to upgrade their vehicle's suspension. So the key to selling performance shocks is (1) knowing what's available from the various shock suppliers and (2) being able to recommend specific types of shocks for specific types of vehicle applications and driving situations.

For example, a customer walks into your store and asks if you have "coil-overs" to fit his Honda. If you don't know what a coil-over is, you're going to have a hard time looking up a product to fit his car let alone make the sale. You need to be product savvy and speak the same lingo as your performance customers.

Coil-overs are one of the hottest upgrade options today for sport compact cars. Essentially, a coil-over is nothing more than an adjustable bolt-in MacPherson strut. It's a shock absorber with a coil spring wrapped around it, and it has an adjustable spring seat plate that can be turned to raise or lower the position of the seat. This changes the spring rate of the coil-over for a softer or stiffer ride. It can also be used to raise or lower ride height depending on the application. There are also "air spring" versions of coil-overs that use a rubber air spring instead of a coil spring to alter spring rate and/or ride height. The shock in a coil-over may be a conventional gas-charged twin-tube design, or a high-pressure monotube design with or without adjustable valving. Some suppliers even sell electronic versions of their coil-overs that allow the driver to adjust the suspension on the fly from a control box mounted inside the car.

IT'S A GAS
To sell performance shocks, you also have to know something about gas pressurizing. The basic idea behind pressurizing a shock is to keep the hydraulic fluid under pressure so it won't cavitate and foam, which leads to "shock fade" (a loss of ride control caused by uneven or decreased fluid resistance). In a nonpressurized shock, the hydraulic fluid can't keep pace with the rapid up and down motions of the piston and is quickly churned into foam. This reduces resistance and the shock's ability to dampen suspension motions. As a result, dampening control lags behind suspension movement and both handling and traction suffer.

By pressurizing the fluid reservoir with nitrogen gas, the formation of bubbles is minimized. The dampening characteristics of the fluid remain constant and shock fade is eliminated. Pressurization also helps to extend the shock more quickly after it's been compressed and at the same time increases its resistance to compression (making it slightly stiffer). Gas charging provides more consistent control, reduces lag, lessens body roll and improves traction recovery on irregular surfaces. That's why gas shocks and struts should always be recommended for upgrading suspension performance.

Most new vehicles come factory-equipped with gas shocks or struts, but these are not necessarily performance dampers. The gas helps, but by itself doesn't create a true performance shock. Generally speaking, the higher the pressure, the greater the resistance to foaming and cavitation. But you can't really compare shocks by pressure ratings alone because performance depends on the design of the shock and its internal valving. There are a lot of differences between shocks, and pressure ratings is only one of them.

Gas shocks come in one of two basic varieties: single tube (monotube) and double or twin tube. The single tube variety has all the major components contained within a single large tube (thus the name) and typically uses a very high-pressure charge (280 to 360 psi). The gas charge is separated from the hydraulic fluid by means of a floating piston in the top or bottom of the tube. This type of shock must be manufactured with a heavier gauge cylinder and a highly polished internal surface (some are Teflon lined).

A less expensive alternative for upgrading ride control performance is the double or twin tube gas shock. Available from many of the same suppliers of single tube shocks, the double tube design is essentially a gas-pressurized conventional shock with lower pressure. Some are in the 70-130 psi range, while others are 112 to 130 psi or higher.

PERFORMANCE VALVING
Many OEM dampers are valved more for ride comfort than ride control. Soft valving provides a nice boulevard ride, but the trade-off is often reduced body control and more roll - exactly what you don't want on a sport compact car, sports sedan, sports car or SUV with a high center of gravity.Valving is what makes a shock a performance shock or a standard shock. It defines the compression and rebound characteristics of the damper as well as its ride control envelope. Some performance shocks are designed primarily for the track and are probably too harsh for a daily driver.

Likewise, some street performance shocks provide significantly better handling than stock shocks, but are not the best choice for an all-out racing application. As we mentioned earlier, you have to match the product to the application - and your best sources of guidance on this subject are your shock suppliers. They design and build the shocks, and they know which products work best in which kinds of driving situations. If they recommend a particular shock for the street or the track, follow their advice.

ADJUSTABLE SHOCKS
One thing to keep in mind about performance shocks and struts is that stiffer isn't always better. What works great on the race track may be too harsh on the kidneys for normal driving on the street. That's where adjustable shocks and struts come in handy.

Adjustable shocks are a good choice for "dual-purpose" vehicles that are driven mostly on the street but used occasionally off-road or for racing or towing. Adjustable shocks allow the driver to dial-in the desired amount of stiffness. By turning an adjustment screw or dial, or rotating the position of the piston rod in the damper, the internal valving is changed to increase or decrease the resistance offered by the shock. The shocks can be set at "normal" for everyday driving, or "firm" or "extra firm" when things get serious. Some aftermarket shocks offer up to eight or more different settings. And some are available with electric motors or solenoids that allow the driver to change settings from the driver's seat.

TRUCKS & SUVS
Owners of trucks and SUVs are typically interested in a different kind of performance shock. They are usually interested in better handling stability rather than cornering agility. When their vehicle is used to pull a trailer, it should maintain a sure-footed track without tail wagging or whipping. The steering feel shouldn't change drastically as the load increases, and the headlights should remain well focused on the road ahead. There should be no bumper dragging, no suspension bottoming, and no steering wander or instability.

Firming up the suspension with a set of performance shocks will help keep the body flat and reduce roll and sway. Excessive body roll when cornering is bad because it unloads the wheels on the inside while causing excessive camber changes on both sides of the suspension (camber is the inward or outward tilt of the wheel that affects tread contact with the road). A more stable vehicle is also a safer vehicle because it allows the driver to make sudden lane changes or take evasive maneuvers with greater confidence.

For those who love to take their vehicles off-road, shocks with increased suspension travel may be required. Off-road vehicles are often raised to increase ground clearance and tire clearance. If the original shocks aren't long enough, they may bottom out and limit suspension travel.















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