Due to its construction, a Bilstein shock has no real moving parts (other than the piston and rod assembly itself). There are no springs or check valves to fail. The monotube design also allows Bilstein to separate the gas-charged chamber with a floating piston, a design that lets them load the shock with up to 360 psi of nitrogen-a higher pressure than conventional shocks. The gas chamber's main duty is to stabilize oil. Stabilizing (with pressure) prevents aeration and cavitation. For perspective, the swirly, foamy mass behind a boat is a result of the propeller cavitating the water.
"Cavitation leads to damping loss. In a shock, the valves are designed to control oil, not air. There will always be air in oil," continued Duck. "When you get people saying, "it's all right at first, but after a while, the shocks start to fade away," that's usually cavitation. He also said, "Pressurizing the oil in a shock prevents that. Very high pressure will eliminate it. People get the idea that high pressure causes harshness, but that's not true."
Bilstein also maintains that the monotube design is an efficient heat diffuser. Since shocks convert kinetic energy to thermal energy, heat is a shock's natural by-product. But "excess heat is an enemy to mechanical things," Steve says. Since a monotube's cylinder is the body itself, the "increased surface area directly on the cylinder translates to greater heat dispersion." And since excess heat causes aeration and excessive wear, "that's a big deal."
Bilstein currently offers more than 20 part numbers in 6 different designs, including standard shocks, chrome shocks, and coilovers-all in varying lengths. And since the company builds each of these rod shocks by hand at its Poway, California facility, it can tailor and valve each one specifically for each application.
At Race Car Dynamics, Duck says, "we have the ability to go outside the normal valving guidelines to work with special applications. We work with people to find out what they want out of the shocks and make those changes. That's what we can get from offering a handbuilt shock." They also have a new line of Classic shocks, which are specifically tailored to the hot rod and kit car market. If you give Duck a call at RCD and answer some questions about how you'll be driving your car, he'll be able to recommend and build a shock with the correct valving for your vehicle.
Obviously, well-designed high-quality products come at a price, but we were surprised at how Bilstein's pricing lined up with the other quality shocks. Considering what Bilstein designs into its shocks and the willingness to cover its products with a lifetime warranty, you could look at the shocks as an investment. And with RCD's commitment to fine tuning your vehicles suspension needs, it turns out to be a win-win situation.
After a tour through the Bilstein facility and a brief rundown on what sets monotube shocks apart, we were informed why Porsche, Mercedes-Benz, GM trucks, and racers from Formula 1 to NASCAR run Bilstein shocks. If nothing else, it might give you something else to look at the next time you're out shock hunting: the inside.