High-End Shock Performance - Shock ValuePosted in How To on February 1, 2010 Comment (0)
Pared down to the basics, a shock is nothing more than a hydraulic cylinder that has internal controls that affect the rate at which the shock extends and compresses. Another way to explain a shock is that it's a device that changes kinetic energy (motion) into thermal energy (heat).
Though the concept is simple, shock performance is the single biggest factor in determining how your rig rides. Shocks determine whether your rig will stick to an obstacle or bounce off of it. Shocks (and lest we forget, suspension and steering geometry) determine whether your rig handles well on the street or is a dangerous handful.
Shocks come in a whole spectrum of prices. We decided to concentrate on high-end shocks this time because they're the most tunable, last the longest, and can make the biggest difference in comfort, safety, and most importantly, fun. Yes, basic shocks cost less and can usually be bolted to the same set of mounts, but you really do get what you pay for.
To hammer the point home, we consulted four industry leaders whose products have hundreds of thousands of off-road miles to their names. Who are those leaders? King Shocks, Light Racing, Walker Evans, and Sway-A-Way.
Turned inside-out to expose their guts, we found premium materials, precision machining, and superior design. Assembled, tuned, and bolted to your rig, they're nothing short of a revelation. They're small parts that make a big difference. We think you'll find that high-end shocks are a big-time value.
Bypass Tubes Explained
Bypass shocks have a sci-fi appearance, but the benefits are down-to-earth. Remember that the shock piston has valving shims attached to the top and bottom of the piston, and that those shims control the speed at which shock fluid can pass through the piston ports and flow around the shims. Bypass tubes let oil flow around (bypass) the main shock body, thereby enabling the piston to travel faster than it normally could. Once the piston has gone beyond the zone influenced by the bypass tube, the piston ports and valving shims resume full control. These two photos show a bypass tube for the compression stroke. As the piston travels upward, oil comes through a pair of chamfered entry ports.
From there, it flows downward through an adjustable check valve, and back into the main shock body through a pair of chamfered exit ports. The spring tension on the check valve is adjustable via an allen key and a nylock lock nut. If the check valve spring tension is increased, the check valve takes more force to open and thus the piston valving shims assume more control, meaning the stroke will be stiffer. If the check valve spring tension is decreased, less force is required to open the check valve, more oil will flow through the bypass tube, and the stroke will be softer. This tunability makes it so that you can adjust the shocks without taking them apart. The single downside to bypass shocks is that they're noisy. The check valves click each time they open. If you want the ultimate in control and adjustability, bypass shocks are for you. If you can't stand the noise, look to shock valving and pneumatic bump stops to control the ride.