Road racers talk about camber gain, roll center, and Ackerman. Drag racers talk about instant center, anti-squat, and pinion angle. Although these are all important factors in maximizing lateral and straight-line grip, optimizing suspension geometry is only half the battle. Unless a chassis can transfer weight—from side to side and front to back—in a controlled and predictable manner, all the effort put forth to optimize geometry could very well go to waste. That’s where a set of high-performance shocks enters the equation. By making the loading and unloading forces placed upon the tires as gradual as possible, shocks very much determine how effectively the rest of the suspension performs. For hot rodders, performance shock options abound, but which is right for your application and what’s the truth behind all the fancy terminology the message board crowd loves throwing around? To find out, we asked Chris King of Viking Performance to explain it all.
Although Viking is a relatively young company, founders Chris and Christina King have over 40 years of collective experience in the aftermarket suspension industry. When they started the company in 2011, they recognized a huge shortfall in the number of affordable double-adjustable shock absorbers in the market. As such, most hot rodders ran non-adjustable or single-adjustable shocks, and Viking’s mission was to make double-adjustable shocks attainable for all enthusiasts. By only focusing on double-adjustable shock absorbers, Viking is able to offer high-quality, double-adjustable shock at a similar price point to a typical single-adjustable shock. To complement its shocks, Viking has engineered its own line of springs and rod ends as well. One of Viking’s most exciting new products is its Berserker active suspension system, which utilizes powerful processors and a series of sensors to automatically adjust shock valving up to 1,000 times per second. Supercar technology previously reserved for Ferraris and Lamborghinis is now available for your muscle car. Shock technology has certainly progressed rapidly in recent years, so let’s dig in to learn more. Here’s what Chris King had to say.
What Shocks Do“Shocks are definitely the key to a car’s overall suspension performance. Some link shock absorbers to the brains of the suspension system. However, at Viking we consider the shock absorber as the heart of the suspension, as both utilize fluid flow to optimize performance. The function of the shock absorber is to absorb and dissipate energy. In terms of overall vehicle dynamics, the role of the damper is seldom fully understood. Vehicle dynamics engineers often talk about the personality of a car and spend countless hours tweaking the damping curve to get just the right feel, which is often different depending on where and how the car is going to be utilized. For example, the tune for Europe is much stiffer and biased towards performance than the American tune, which has historically been all about comfort in a straight line. Body roll angle in a corner is determined statically by a combination of the spring rates and the antiroll bar. For a given cornering acceleration, the body rolls until the roll stiffness multiplied by the roll angle equals the cornering acceleration multiplied by the roll moment arm. The damper cannot affect the eventual roll angle, since damper force is a function of relative velocity, not relative displacement. However, it can control how the body gets to its eventual roll angle. In general, low roll damping feels alarming because the roll rate is high, and there is usually some overshoot and oscillation. A well-damped vehicle feels very progressive and the vehicle will stabilize at its roll angle more quickly, which adds to the driver’s confidence. This also results in more constant tire patch contact force, which in terms of vehicle dynamics is the dampers main job. Tires produce a traction force, which is roughly proportional to the contact force up to the limit of adhesion. If this force is varying wildly during the entry into a corner, the steering balance of the vehicle will also vary, which is extremely upsetting to the driver’s confidence. The same can be said in pitch during hard acceleration and braking, so at the end of the day the dampers real value is that it keeps the tire on the ground and the normal force as constant as possible.”
Twin- vs. Mono-tube“There are definite benefits to both twin-tube and mono-tube shock designs and there are some high-quality shocks in the marketplace of both designs. Many races and championships have been won over the years with each design. However, for Viking’s target market we strongly feel that the twin-tube provides much more flexibility, benefits, and a higher value than the mono-tube design. In our opinion, the twin-tube flat-out performs better in drag racing, street performance, road racing, autocrossing, and just plain old cruising. Mono-tube shocks, by design, have rod force at all times due to being gas pressurized. Twin-tube shocks are unencumbered by rod forces since they utilize a gas bag instead of gas pressure. A vehicle operating on dry, slick asphalt surfaces will respond better utilizing a shock absorber that does not have the unwanted rod forces from the gas pressure in a mono-tube shock absorber. The twin-tube design will maximize tire contact. If you look at a basic setup for a street application, ride quality is going to be optimized by having a softer compression setting. This allows the suspension to absorb the bumps without knocking your teeth out, while also utilizing firmer rebound settings to keep the car from continually oscillating down the road. This is even more prominent in the front end of a car where you are dealing with the motion ratio of an independent suspension, and therefore fighting a higher spring rate. A standard mono-tube shock has the opposite effect of what you want the shock absorber to do, as you have now added rod force, which is like increasing spring rate. This adds compression forces, which require even larger rebound forces to control the energy and return the vehicle to ride height in a timely manner.
“In contrast, off-road trucks or dirt circle track racers may prefer the gas pressure of a mono-tube shock absorber to assist in keeping the vehicle from planting the tire into the rough surface. There are ways to decrease rod pressure in a mono-tube shock, such as through the addition of a base valve. However, this is where value comes into play, as features such as these drive the cost of the mono-tube shock much higher. Furthermore, twin-tube shocks allow fitting a longer piston rod, which nets increased stroke in a twin-tube shock absorber within the same shock body envelope. This is due to the gas chamber required in the mono-tube design that is not necessary in the twin-tube.”
Double-adjustable Advantage“The twin-tube shock design also fits in very nicely with our goals when we started Viking. We saw a huge shortfall in the number of double-adjustable shocks being utilized in certain markets, mainly due to substantial price premiums for these types of shock absorbers. We felt the majority of the market was unable to optimize the shock settings on their vehicles, and were stuck with overall ride quality and handling that was far from great. To get the best in performance and ride quality, the compression and rebound valving must be independently tuned with a double-adjustable shock. At Viking, in order to provide the highest value double-adjustable shock absorber, there was no other option except a twin-tube design. This design allows access to both the compression and rebound circuits in the base of the body. In contrast, on a standard mono-tube shock, the gas pressure resides in the base of the body. As a result, when adding adjustability to a mono-tube shock, these shocks are generally only rebound adjustable via a gun-drilled piston rod, which is very expensive. In order to access the compression side independently of rebound, a canister is added, resulting not only in mounting issues, but significant cost increases. For us, easy access to both compression and rebound adjustments is one of the main benefits of the twin-tube over the mono-tube. Another huge benefit of the twin-tube is the large adjustment range in the shock absorber. When adjusting via a gun-drilled piston rod, the pre-determined range is much smaller than the range provided in the twin-tube design. Further, the end user must understand and define the adjustment range prior to ordering the mono-tube shock, since the window of adjustability is so much smaller.”
Valving“Drag cars, road racers, and street cars all have different needs in terms of shock valving. However, it does not stop there. Driver style and capability, track and road conditions, vehicle type, vehicle weight, horsepower, and tires all create different needs in terms of shock valving.
“It is extremely difficult to provide the exact ideal compression and rebound shock settings for a given vehicle and driver on any given day. However, Viking does provide a very good place to start. That is the ultimate beauty of having a double-adjustable shock, as you are able to tune for your specific needs. For drag racing, the racer needs to understand how he wants the car to react. Based on all the factors already mentioned, does the racer want to maximize weight transfer? If so, the front will be set with a stiffer compression and soft rebound, while the rear will have a soft compression and stiffer rebound. If the racer wants to limit weight transfer, the setting will go in the opposite direction.
“The same variables above will come into play for road racing. It is easier to narrow the range of adjustment for road racing versus a drag race setup, but various factors will still need to be considered, as the rear settings on a pickup truck will vary quite a bit from an early A-body.
“For street cars, the settings get easier yet to define. Ride quality is optimized by having a softer compression setting in order to allow the suspension to absorb the bumps without knocking your teeth out, and it’s matched with a firmer rebound setting to keep the car from continually oscillating down the road. This is even more prominent in the front end, where you are dealing with the motion ratio of an independent suspension and therefore fighting a higher spring rate.”
Compression vs. Rebound“The compression side of the shock valving controls the force required to push the rod into the shock absorber. On a car, this equates to how it feels when you hit a bump, pothole, or other rough terrain in the road. A softer compression setting will allow the car to have more suspension movement and to come down in the front or squat in the rear. Too soft of a setting may cause the vehicle to easily bottom out. This will result in a higher roll rate, which may cause the driver to feel less confident. Too stiff of a setting will result in a jaw-jarring feeling when going over bumps. It will also result in a less than ideal tire patch contact.
“In contrast, the rebound valving controls how quickly the shock extends after being compressed. A higher spring rate will cause the shock to extend quicker, as there is more stored energy, thereby requiring a higher rebound setting. The softer the rebound setting, the more the car will oscillate before returning to the vehicle’s natural ride height. A stiffer rebound setting will result in the vehicle slowly returning to ride height. Again, too soft of a setting will result in a higher roll rate, which may cause the driver to feel less confident. Too stiff of a setting may cause the vehicle to ratchet itself down as it proceeds down the road, and the shock never allows the vehicle to return to normal ride height.”