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Do-It-Yourself Projects
Adjustable Shocks
By Wayne Scraba/
Printable version
Degree of DifficultyModerate
Estimated Time180 minutes
180 minutes
Taking Turns for Better Handling -
Shock absorbers (or dampers, as some call them) are, in effect, hydraulic devices that resist chassis movement by passing oil through a set of orifices and valved passages. Inside an adjustable shock, manipulating the fluid movement through the valving of the shock changes the dampening characteristics. That means you can control how the suspension in your car or light truck functions (essentially fine tuning it for a given application). Many quality externally adjustable shocks are rather similar when it comes to adjustment. Once installed in the car, all changes are usually handled externally by way of the adjustment knob. After installation, the knobs on each of the shock absorber are accessible, either through the side of the spring (typical front applications) or on the body (typical rear applications).
Adjustable Shocks
Now what about the terms you usually hear when someone discusses shocks. The words “bump” and “rebound” (or “compression” and “extension”) are often used. What’s with that? Different shock absorber manufacturers use different lingo. Regularly, the terms "bump," "rebound," "compression," and "extension" are used interchangeably. Here’s how it works: A shock absorber travels in two directions. It gets shorter (compresses) and it gets longer (extends). Some shock absorber manufacturers call this "bump" and "rebound," but that can get confusing. To get a grasp of what this is all about, pretend that you drive your car over a good old-fashioned parking lot speed bump. As it hits the speed bump, the action "bumps" the shock, which, in turn, compresses it. After you drive over the speed bump, the shock rebounds and extends (extension), allowing the wheel to move downward in the chassis. That’s where we get the terms “bump” and “rebound.”
Plenty of shock absorbers available today are adjustable externally. By far the most common are single adjustable. That means one knob is used on the body of the shock, and it controls the internal shock absorber valving. Adjustment is obviously a good thing since it allows you to physically “tune” the suspension in your car. But what’s right?
Making Adjustments
The basic single adjustable shock setup works like this: Turn the knob fully to the softest setting (typically, this proves to be counterclockwise). The "end" of the adjustment (where it will not turn and click any further) is the softest setting, and it’s often termed position 1. By turning the knob clockwise, each click will increase the shock resistance. On the other hand, the full stop counterclockwise has valving that's similar to a 90/10. What’s a 90/10? It’s an old drag race shock designed so the front end of the car would rise rapidly as the car accelerated then settled down slowly. The thought here was that weight would transfer quickly to the rear wheels and stay there. In other words, the front of the car is very “loose,” particularly when it comes to rebound (extension), but relatively stiff when it comes to bump (compression). As you can imagine, that sort of setting (or non-adjustable shock) isn’t much fun on the street, but it does go to show what the “softest” setting accomplishes on many adjustable shocks.
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