AFCO Takes Us To School – Dirt Racing Shocks 101

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How many times have your friends called you crazy for participating in your sport? If a few wins would make you appear a little more rational in the eyes of your friends and critics, try a little shock therapy; it might just help.

Shocks are the least understood facet of suspension – Ben Baker Of AFCO Racing

Keeping your butt in the seat, your wheels on the ground, and your body out of the chiropractor’s office may not seem like rocket science, but for our friends at AFCO Racing, it’s exactly that.

If science was never your strong suit, don’t worry. Consider this feature on Dirt Track Shock Technology 101 your crash course and cliff notes. Ben Baker of AFCO Racing is a jet propulsion engineer; I kid you not. And most importantly, he literally has your back. Baker is able to break down the ins-and-outs of the shock science into simple terms, bridging the gap between rocket science and racing, because he started out as a dirt track racer and pit crew member, himself. 

Who better to give the lowdown on properly tuning and setting up shocks for a night of dirt track racing, than a dirt track racer turned rocket scientist?

Meet Your Shock Therapist, Ben Baker, of AFCO Racing


Ben Baker of AFCO Racing

Jet fuel raced through Baker’s veins at an early age. At fourteen, Baker ventured into the race pits as a crew member for the late model dirt track racer, Allan Rettig. Baker’s interest in engineering and technology persisted. After college, he found himself in a government lab conducting jet propulsion tests. While challenging, he felt unsettled in the sterile environment of a government laboratory. He did not understand it at the time, but he was going through some serious track withdrawal.

Mark Bush, founder of AFCO Racing, was quick to diagnose Baker. The veteran and racing products CEO quickly injected racing back into Baker’s veins by offering him a position with his company. Bush’s prescription of dirt, mud and asphalt worked – and Baker responded. He traded in his lab coat for an AFCO fire suit.

AFCO Racing is a “working-class” business, specializing in the design and manufacture of high-quality racing products, including: shocks, springs, cooling and brakes. They combine quantitative analysis and sophisticated 3-D product design and engineering, with dyno and track testing and racer feedback, in order to stay competitive and precise on and off the track.  Their unique model allows them to their keep costs down by forgoing the big sponsorship deals and conducting their research in person, on the track, and through one-on-one therapeutic sessions with people like you.

Baker spends a minimum of 160 days a year providing shock therapy to fellow racers, owners and crews. Baker says, “I love meeting with customers, testing products, and performing installs. While this takes time and money, it is the only way to learn what really works on track.”   

Normally, Baker starts his diagnostics with a new racer by understanding your current set-up and configuration. He places your existing shocks on the dyno to capture baseline data. If desired, Baker and the AFCO technicians can then fine-tune your shocks so they accurately match the settings of your originals. The guesswork is gone.

Baker reminds us, “Shock absorbers affect the control of your car as much as any other suspension part. Yet, shocks are the least understood facet of suspension. Mechanics often rely on shock recommendations from others or, even worse, choose not to pay any attention to the topic of shock selection. If your mounted shocks are unsuitable, future chassis adjustments will improperly be made in a futile attempt to compensate for poor shock selection. This can result in reduced performance for the driver and frustration for the crew.  However, if a team understands shocks and handling, a well-tuned car can gain 1/10th-1/20th a second per lap on the competition on a ¼-mile track.”  

According to Baker, “This adds up over time. It can also save wear-and-tear on the car, and the driver.”


Making the right shock choices at the track is crucial to your success. However, Baker constantly reminded us that shock selection is just one part of a huge recipe that equals success on a track. Every choice you make for setup works in conjunction with your shock selection to be competitive.

Shocks 101

At its core, a shock absorber is a device crafted to resist change. When stimulated or pushed, the fluid inside the shock is forced through a series of small cavities on a piston. Some of these holes are always open (permitting fluid to pass through under mild pressure), while others are shielded and only allow hydraulic fluid to pass at moderate or high-pressure levels. Since there is dense hydraulic fluid encased within the cylindrical tube and on both sides of the internal piston, the shock system, as a whole, resists movement.

If your mounted shocks are unsuitable, future chassis adjustments will improperly be made in a futile attempt to compensate for poor shock selection. This can result in reduced performance for the driver. – Ben Baker of AFCO Racing

More specifically, the size of the cavities and the pressure levels at which the shielded holes become unshielded or opened, determines the stiffness of the shock. As a rule of shocks: the greater the force, the greater the amount of fluid, and the greater the resistance. To make sure a shock meets all of your racing performance criteria, the AFCO shock dyno team tests a shock’s resistance at a minimum of three different levels. The diagnostic team emphasizes the importance of evaluating a shock’s resistance at mild, moderate, and high pressures.

Baker further explained to us that low piston speed and pressure dyno simulations will simulate how shocks will perform in the corners. Moderate and high piston speed and pressure dyno simulations will establish how well a shock will handle bumps and ruts.

Rebound and Compression

Rebound is a shock’s resistance to expansion. Rebound will affect how quickly the tire is unloaded or returned to its original position. Compression is a shock’s resistance to compacting. Compression control will determine how the suspension will react under load, or when encountering a bump.

If your series allows it, AFCO has adjustable shocks that allow you to adjust the rebound and compression on the fly.

“50/50” shocks are shock absorbers that have equal rebound and compression settings. Split valve shocks are shock absorbers with unequal rebound and compression. For example, a shock that has 80 percent of its total stiffness in compression control, and 20 percent of its total stiffness in rebound control is an “80/20″ shock. Like shock stiffness, the ratio between rebound and compression will greatly influence handling.


Navigating bumps and ruts that form in the track is vital to your success. You won’t always be the leader, to pass cars you will have to go out of the preferred line and deal with some track conditions.

Balance and Timing

Do not overdo it. If your suspension is too stiff, your tires will begin absorbing the bumps. If your tires are serving as your suspension, they will not keep contact with the track. According to Baker, “When you lose touch with the track, you lose RPM. Ideally, when a quick moving car tire strikes a large bump, the suspension should respond smoothly and with as little change in the stance of the frame, as possible. This allows the tire to hold.” However, if the firmness is too great or the spring is too taut, the tire will jump whenever encountering a bump or major rut. If the suspension is exceedingly solid, the whole car can actually bounce and the tire will lose contact with the surface.


Shocks can seem extremely complicated, but the folks at AFCO will work with you to determine what type of shock build you need to be competitive week in and week out.

Keep in mind that in the “bump” phase, the spring is actually working in conjunction with the shock to resist rebound. However, in the “rebound” phase, the spring is working against the shock. The spring is trying to spread the shock and push down the suspension. This illustrates why most 50/50 shocks will have more rebound than compression at speed.

If the rebound is too stiff, the shock will not allow the spring, and thus the suspension, to return to its original position quickly after a bump or rut. The tire has now lost contact with the track. In this scenario, the shock can literally hold a tire off the track for a brief time. According to AFCO, this can cause your car to skate up the racetrack whenever encountering bumps and ruts. The fix is softer shocks, assuming your springs are not too firm.

Still, do not go too soft on us! Your car will experience wheel hop if things get too soft. Wheel hop begins when a bump or rut causes the suspension to move violently, causing your tire to actually bounce off the track. When wheel hop occurs, the coil is in an over-compressed state and briefly stores up an enormous amount of energy. When released, the tire violently slams back on the race surface and begins bouncing like a basketball. Assuming a smoother track past this point, the tire will repeatedly bounce, dispensing a little less stored energy each time. This uncontrolled progression will last until the shock can catch-up and control the energy in the spring. The cost of wheel hop is a loss of traction, resulting in a loss of speed.

Baker summarizes by saying that, “A shock is a timing device. Tire plant is critical to turning faster laps.  Good shocks will keep your tires on the ground, and your RPM up.”


Shock fade is a condition where loss of dampening action occurs because of liquefied frothing inside a shock absorber. AFCO is constantly testing for shock fade. To combat this, AFCO uses their dyno to conduct simulations. AFCO tests to a 10,000-lap standard. Balancing the life of a shock with the potential for fade is a constant undertaking.

Ben Baker brags about the quality of AFCO shocks, “Heat is the enemy of a shock. During a recent real world test on a 100-degree day, AFCO shocks traveled over 100 laps on a mile dirt oval, and only reached 130 degrees at the conclusion of the race.”


AFCO’s shock assembly featured above, at their headquarters in Boonville, Indiana.

AFCO Shocks – Setup and Maintenance

AFCO Racing provides an affordable and high-quality line of shocks, engineered specifically for circle dirt tracks, slick and rough track surfaces. With AFCO Racing Products, commitment begins right out of the box. When you unpack your new TwinTube or MonoTube shocks, you will find a detailed tuning guide. Research and testing went into the suggested shock settings already in your hand. And, that commitment and testing continues, as they encourage and welcome racer feedback. Additionally, if AFCO does any work on a shock, they will drain and replace your shock fluid for you.

As the race season progresses, AFCO suggests crews have their shocks serviced and change fluids halfway through the season. If racing several times a week, consider two comprehensive inspections with fluid changes per season. As a best practice, check your shocks weekly.

The crash course that Baker and the folks at AFCO Racing provided us on shocks gave us a better understanding of dirt track shock technology, and another advantage for when the rubber meets the ground, and stays down. 

Article Sources

About the author

John Gibson

John has been around dirt track racing his entire life. In fact, he was almost born at Monett Speedway in Monett, Missouri. He has raced everything on dirt and asphalt from karts, to Indy cars, to 650 horsepower stock cars in the USAR Pro Cup where he currently races.
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