Dirt Modifieds

Left Rear

The new FPORS designed for left rear shocks have been a big improvement to this corner of the racecar. Excessive gas pressure makes the chassis hop like a pogo stick bouncing on and off the limiter chain. This shock requires less gas pressure than even a base valve shock. The left rear shock’s main function is to hold the left rear up under deceleration or part throttle conditions. A standard left rear shock that would require 125 psi. to 250 psi. in gas pressure can be built in the FPORS design with 50 psi. to 75 psi. The FPORS shock can be built with any valving curve to fit your valving requirements on the left rear suspension.

 

Right Rear

Midway in the 2026 season we developed a new right rear shock valving for dry slick tracks. Problem: When tracks get slick and the chassis requires side bite. Mechanics are increasing R.R. Spring rate by adding spring rubbers or installing a stiffer spring. This helps side bite but now hurts forward bite because the stiff springs kills forward bite. Solution: We created a dry slick only shock that sticks the right rear tire on corner entry and has great forward bite. Now it is not necessary to add excessive spring rate to the R.R. and kill your forward bite. You cannot run this shock when the track is fast and heavy because it will make your chassis way too tight.

The standard right rear shock is still great for fast/heavy track conditions. This shock has more high-speed control to stop the oscillation in the rough. Both shocks have plenty of rebound adjustment range to fine tune for the changing track conditions. We always mark your dyno sheets for recommended settings for track conditions.

 

Right Front

The right front is possibly the most important shock on the car. The rebound dampening in this shock controls the chassis attitude throughout the corner. Too much rebound hurts forward bite, and too little rebound unloads this corner creating a push condition. It is important to have enough low speed rebound to hold attitude but not too much high-speed that it makes this corner too rigid.

The low-speed compression needs to be soft enough to allow the chassis to get down on corner entry and enough high speed to keep the chassis from slamming the bump stop on corner entry. We have built special pistons just for the right front shock to accomplish these requirements.

This corner is very critical on shock and body lengths for different chassis builders. The right front shock body needs to hit the bump stop at the right time and rate.

 

Right Front bump stops

The foam Christmas tree bump stops are the most tunable for the right front corner. We sell a soft, medium, and hard durometer. We also have urethane bump stops at several different rates, but they are very progressive spring rates. This makes the tuning window of choosing the correct rate and travel very narrow unless the track is always the same.

 

Left Front

The left front shock is available with an internal droop spring (in series that allow internal droop limiters) to hold cross weight in the chassis. The internal spring length depends on what chassis you are racing to make sure the engagement is correct. The L.F. rebound and the internal spring holds cross weight in the chassis, which creates forward bite. Too much rebound pulls the tire off the ground and makes the chassis push mid-corner to exit.

After we dyno your shock, we will send you dyno sheets showing your complete adjustment range and recommend adjustment position.

 

SHOCK DYNO TESTING SERVICE

Now that the racing season is over, this is the ideal time to start preparing for next season. Many of our customers send all their shocks in to be dynoed at this time of the year, so that they can be checked after a long season of racing.  To encourage all our customers to assess their shocks’ condition before the next season, we’re offering a reduced cost for shock dyno services on any A.R.S. shock—only $10 per shock until January 31, 2027. This reduced shock dyno offer will give you a chance to evaluate the condition of your shocks after a season of racing and at the same time review any new valving combinations.

When sending your shocks to us for service, please enclose a note with return address, phone number, and a brief description of what you would like done to your shocks. A shock maintenance form is available from our website. After the shocks are dynoed, we can call you with the results and discuss the outcome of your shocks or any new shock combinations. Many customers send all their shocks to us during this special dyno offer, so send your shocks in as early as possible to avoid any delays in preparing for next season.

Package 1 – $2,600
($2,710 with one C/O Kit)

Fronts & RR – 7200 series Rebound Adjustable shocks

Left Rear – 7200 series Compression Adjustable shock

This shock package contains 3 rebound adjustable shocks (L.F., R.F., & R.R. plus the left rear compression adjustable shock. All shocks are 7200 series base valve design. The shocks can be built with adjustable eyes or non-adjustable eyes that need to be removed for adjusting. Some Modified rules require removing the shock eye to adjust the shock.

Left Front

Left front adjustment allows you to fine tune the rebound to hold cross weight in the chassis which creates forward bite. Too much rebound dampening pulls the tire off the ground and makes the chassis push mid-corner to exit.

Right Front

Right front rebound controls the chassis attitude throughout the corner. Too much rebound hurts forward bite, and too little rebound unloads this corner creating a push condition. It’s important to have enough low speed rebound to hold attitude, but too much high speed rebound makes the chassis too rigid. The special right front piston allows the chassis to get down and turn on corner  entry and still have enough high speed compression to keep the chassis from slamming down.

Left Rear

Left rear shock is compression adjustable to provide enough range to hold the chassis up and make sure the left rear corner does not fall down and lose attitude. Too much compression makes the chassis too rigid which hurts traction. Too little compression will allow the chassis to fall too quick and lose rear steer. The base valve in this shock allows you to reduce the pressure and not make the chassis too rigid.

Right Rear

Right rear shock is rebound adjustable which allows you to soften the rebound enough for heavy track conditions and stiffen the rebound for maximum traction. We lock in the compression dampening and adjust the gas pressure for heavy to dry/slick tracks. We adjust this shock more than any shock on the car to accommodate changing track conditions.

The Schrader valve can be removed and plugged if required by your racing series rules.

Package 2 – $1,850
($1,960 with one C/O Kit)

Fronts & LR – 7200 Series Mono Tube Non-Adjustable Steel Shock

Right Rear – 7200 Series Mono Tube E-Model Adjustable Steel Shock

 Fronts & Left Rear

The 7200 Series shock is a large steel body mono-tube (gas) shock. This shock uses CNC machined aluminum internal parts designed for racing with no aftermarket parts.  This shock is designed for racers that are required to use a steel body.  This shock contains the latest base valve technology to provide low rod pressure which maximizes traction.  The advantage to the low pressure design is for when the racetrack becomes slick and tires lose their grip, the pressure is not increasing.  This provides more consistency from the first lap to the last lap by decreasing spring rate build up in your shock.  This shock comes with a Schrader valve to fine tune the gas pressure.  If your race series will not allow Schrader valves, the shock is available with pressure pre-set and cap in the port hole to make it legal. This is a Non-Adjustable shock. This shock accepts 2 1/2″ & 5″ O.D. Springs and is available in 6″, 7″, 8″ & 9″  shaft lengths.

Right Rear

The 7200 Series shock is a large steel body mono-tube (gas) shock. This shock uses CNC machined aluminum internal parts designed for racing with no aftermarket parts. This shock is designed for racers that are required to use a steel body. This shock contains the latest base valve technology to provide low rod pressure which maximizes traction. The advantage to the low pressure design is for when the racetrack becomes slick and tires lose their grip, the pressure is not increasing. This provides more consistency from the first lap to the last lap by decreasing spring rate build up in your shock. This shock comes with a Schrader valve to fine tune the gas pressure. If your race series will not allow Schrader valves, the shock is available with pressure pre-set and cap in the port hole to make it legal. This is a E-Model Eye Adjustable shock. This shock accepts 2 1/2″ & 5″ O.D. Springs and is available in 6″, 7″, 8″ & 9″ shaft lengths.

Package 3 – $1,600
($1,710 with one C/O Kit)

All Four Corners – 7200 Series Mono Tube Non-Adjustable Steel Shock

All Four Corners

The 7200 Series shock is a large steel body mono-tube (gas) shock.  This shock uses CNC machined aluminum internal parts designed for racing with no aftermarket parts.  This shock is designed for the racers that are required to use a steel body.  This shock contains the latest base valve technology to provide low rod pressure which maximizes traction.  The advantage to the low pressure design is for when the racetrack becomes slick and tires lose their grip, the pressure is not increasing.  This provides more consistency from the first lap to the last lap by decreasing spring rate build up in your shock.  This shock comes with a Schrader valve to fine tune the gas pressure.  If your race series will not allow Schrader valves, the shock is available with pressure pre-set and cap in the port hole to make it legal.  This is a Non-Adjustable shock.  This shock accepts 2 1/2″ & 5″ O.D. Springs and is available in 6″, 7″, 8″ & 9″ shaft lengths.

Package 4 – $1100
($1,210 with one C/O Kit)

All Four Corners – 2200 Series LB Twin Tube Non-Adjustable Steel Shock

All Four Corners

The 2200 Series shock is a large body twin tube steel shock.  This shock uses CNC machined aluminum internal parts designed for racing with no aftermarket parts.  This shock was designed to fir the rule of “Steel Body Shock” that saves the racer money.  This shock in Non-Adjustable.  The smooth body shock will accept a coil-over kit that slides over the body.  The large steel body shock accepts 2 1/2″ & 5″ O.D. Springs and is available in 6″, 7″, 8″ & 9″ shaft lengths.