Sorting out one’s suspension takes time, patience, some technical understanding, and the right sources to guide us. With help from KONI‘s Lee Grimes and Performance Shock‘s Bruce Ritchie, we discover how shock valving is one of the misunderstood parts of suspension setup, what it’s job is, and how to use it to perfect our own car’s handling.
A damper must perform several fundamental tasks. It must make the car responsive and, through rebound control, maintain a level platform. Simultaneously, the right amount of compression is needed to press the contact patch firmly into the ground.
To achieve crisp, reassuring handling throughout a range of speeds and situations, a damper must prioritize different functions depending on a damper’s piston speed.
- At very slow damper speeds, often the oil isn’t moving through the piston valves but through the low-resistance bleed holes (approx .010 to .015-inch) in the piston or piston rod. These are usually slow movements like light rolling and pitching.
- Then, once the piston moves fast enough, the focus shifts to managing quicker bodyweight transitions and controlling subtle road undulations. At this point, increasing control forces are generated with the resistance of the piston valves.
- Once the piston is moving very fast, the aim is to increase or restrict oil flow depending on the force curve one is looking to achieve. This is done by adding more piston valves or orifices.
Shock Cutaways Explained
On the twin-tube rebounds adjustable shock (B),
· Bleed orifices are A (inlet) and C (exposed depending upon adjustment setting)
· Piston orifices are D and E
· Piston Valves are 8, bypass springs are 9, and adjuster nuts is 10
Compression side (non-adjustable in this drawing):
· Compression footvalve is 7
· Compression orifices are K and L
· Compression valves are 21
On the KONI 30 series rebound adjustable mono-tube high pressure gas shock (C) ,
· Bleed constant orifices are G and F (exposed depending upon adjustment setting)
· Rebound valves stack is 14
Compression side (non-adjustable in this drawing):
· Compression valves are 12 and 13
The Aims of Valving
Most of the time, revalving is done when the owner decides to refine their suspension setup to the utmost. This may likely include an increase in spring rate (and therefore, “ride frequency”), so replacing the valving components to generate stiffer rebound damping forces will better control the unloading spring. Also, revalving can help get more tire grip depending on the tire used; racing slick tires will work better with more compression damping than DOT tires will.
Rebuilding Versus Revalving
The two terms get confused, so it’s worth defining them before delving any deeper. Typically, the rebuilding process means replacing valve components, seals, piston bands, and the oil. Depending on the way the vehicle is used, it could be over-sheared or simply depleted, so therefore replacing the oil with high quality, damper-specific oil can be helpful.
Suiting the Customer’s Needs
Revalving is reserved for projects a bit on the extreme side, so it follows that revalving is usually tailored to a specific build. To ensure his customer’s demands are met, Bruce Ritchie asks his customers these revalving-related questions prior to building them a damper:
- What goals are you looking to achieve with the revalve?
- Which form of motorsport are you participating in?
- Which tires are you using?
- Which springs are you using?
For drivers using highly-modified machinery, the required information grows:
- What is the sprung and unsprung weight of the vehicle?
- What are the motion ratios?
- What are the size of the sway bars and are they adjustable?
- What racing experience do you have?
With the answers to these questions, they can extrapolate out a valving graph and precisely determine the right course of action.
The Right Categories for Revalving
In classes which stringent rules prevent spring changes, a clever driver can try a few revalving-related tricks.
“In a Stock/Street class, you’re forced to run an OE spring, which [is] almost always undersprung. However, you can use a fairly sticky tire, and that poses a few setup-related issues,” Lee Grimes instructs us. Fortunately, there is a way around.
“By increasing the compression damping, they can fake the car into acting like it has an increased spring rate,” he adds. “It will work the tire compound and carcass harder, and it will be quicker to take a set with more peak grip.”
Though this is considered a patch job, it does work—particularly on the autocross where crisp direction changes through the short corners present are crucial.
“Class rules permitting, ideally you would prefer change to the right spring rate to support the weight of the body, especially for a road course with longer corners where that spring support is needed. Additionally, the tire and road surface must provide sufficient grip, and if not, too much compression damping can cause hopping/grip issues,” he warns.
Revalving one’s shocks is mainly for those looking to find those last valuable tenths or are running in a category with fewer regulations, so the beginner may not need this know-how. For many, a sorted set of shocks should do, but it doesn’t change the fact that this is a step that every self-respecting car nut should at least understand on a cursory level. Thanks to these experienced men and their advice, we’ve gotten just a bit closer to understanding how to find a sweet setup which makes the lap time come to us.