The shape of the damping curve can be precisely tailored with great flexabilty by changing the diameter, thickness and contour of the washer valve stack, the size of the orifices drilled into the piston and the amount of concaveness of the pistons sealing surfaces.
The Ground Control shock can be adjusted for both compression and rebound damping by a slotted shaft running up the shock's main shaft, which controls the size of the shocks major bleed orifice. In a very easy-to-reach, convenient way, the shock can be adjusted at the very top of the shaft by turning the two stacked knobs at the very top end of the shaft; a red knob adjusts for rebound and a blue knob controls compression. This beats the typical, hard-to-reach adjusters used by most racing shocks.
To help prevent bubble-forming cavitation, to increase the Redline synthetic hydraulic fluid's boiling point and to give room for the shock shafts displacement under compression, a floating piston separates the oil from a chamber full of high-pressure nitrogen, filled to about 200 psi.
Separating the oil from the gas allows for the valves to flow only fluid, which improves damping action. In conventional shocks, the oil is mixed with enough air to allow for the shock shaft's displacement. Sometimes bubbles pass through the valves, creating dead, undamped spots within the damping curve.
Since conventional shocks aren't pressurized, it's easy for the fluid to have localized boiling inside the shock under rapid shaft motion due to cavitation. Also, since the shocks don't have more than ambient pressure, it is possible for the fluid to boil itself under extreme use.
The nitrogen pressure can be easily adjusted through a schrieder valve at the bottom of the shock. Sometimes this can be a useful tool to increase the suspension's preload without changing the spring rate and/or ride height, or the gas pressure may need to be increased to prevent foaming and boiling under severe conditions.
The shocks feature high-overlap Teflon bushings to reduce static seal friction-or sticksion, as engineers call it-and to also ensure a long service life. Low-tension Teflon oil seals with built-in scrapers also ensure long, leak and sticksion service intervals.
The shock's body is machined from lightweight 6061 aircraft aluminum, then hard anodized inside and out for corrosion and wear resistance. To prevent a harsh, chassis-unsettling jolt when bottoming out, the shocks have a trick microcellular urethane bumpstop. This soft material is shaped to provide a controlled progressive stop to the end of the wheels travel.
MCU bumpstops have made a huge difference on some of our other project cars and we think it's great that Ground Control has provided them as standard equipment. Ground Control shocks were twice as light as the stock shocks were. This can go a long way in reducing unsprung weight.
The shock's body is threaded externally to accept Eibach ERS racing 2.5-inch coil-over main and tender springs. The spring hats and adjusting collar hardware are machined from 7075 aluminum and hard anodized for wear and corrosion resistance. The Ground Control Advance Design shocks are designed to be simple to rebuild and maintain. With a few tools, you can even revalve, rebuild and repair the shocks at home. If not, you can simply send them back to Ground Control for a quick rebuild.
SpringsSince we are SE-Rious about eliminating lean and understeer in the corners, we used stiff Eibach ERS 450 in/lb front racing springs with a 350 in/lb ERS rear spring. These rates are only slightly softer than what is run in a NASA SE-R Cup racecar.
Even though these springs are more than three times the stiffness of the stock springs, as we have found in the past, stiff spring rates are essential for keeping lowered cars off the bump stops for consistent handling. Even though the ride is quite firm, it is still more comfortable than our bouncing, overly lowered old suspension.