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Shock Technology, Micro & Mini Sprints

Text added 11/2011
As many of you have seen on my new car I have a full set of shock potentiometers. These data collecting devices allow me to evaluate exactly what my car is doing, how it is moving around. From this I can determine what the car needs and when it needs it. Using this data I have a new  shock package that offers an advantage on all size tracks.  This new shock valving offers less car hop on a wet track, a tighter can on the first half of the corner, the ability to run the car on a cushion without the car balling up on the right rear. They also virtually eliminate the need for a bump rubber if you use the new left rear shock. These changes are made through advanced technology pistons, change in shock bleed, and a different shim stack. You can view the shocks in the online store here.

Hyper Racing now revalves monotube shocks in house and tests the rebuilds on our Roehrig shock dyno.

Shock Article
Shocks are one of the most important parts of your race car. As time goes on it seems more and more emphasis is put on developing the correct shock valving. Although shocks are relatively small in size, their function and complexity is far above the normal human. It is one of those scientific fields where you do not need to understand everything, just that which affects you. On this page we will discuss much of what you need to know about Shocks.

What is a the Purpose of a Shock?
The suspension system controls movements of the chassis when the wheels hit bumps, or during natural weight transfer when the chassis is accelerating, decelerating, or negotiating a turn. Shocks and springs work together to control how the chassis moves. The springs (torsion bars) control how much the chassis moves (the final maximum travel) and also have an effect on overall chassis ride height. Shocks control the speed of extension and compression of the spring during its travel or weight transfer. A stiffer shock will slow down a spring's action; a softer shock will allow the spring to act faster.

• The primary purpose of the shocks and springs is to make the chassis stable and predictable while driving over bumps or ruts. If the shock/ spring combination is too stiff, the tire can be pulled off the track surface for a period of time, eliminating that tire's traction ability. If the shock/spring combination is too soft, the chassis can bottom out on the track, again hindering traction. This loss of traction in both scenarios can cause the chassis to skate and make the chassis unpredictable and difficult to drive. Also, it can make it impossible for the driver to tell if the chassis is tight or loose.
• The secondary purpose of shocks and springs is to control weight transfer while executing a turn. Springs control how much weight and shocks control how fast. The faster the weight is transferred to the rear under longitudinal acceleration, the tighter the car will be accelerating forward (forward bite, or forward drive). The faster the weight transfers to the right rear, the tighter the car is coming off the turn. Stiffer springs will transfer more weight to the rear as a result of a higher center of gravity (see the Rethink Dirt page for further explanation of this). A softer right rear and/or stiffer front spring will tighten the car in the middle of the turn (lateral traction or side bite).

Shock Terminology
“Dampening” or “damping” means “to depress, reduce or lessen.” These terms can be used interchangeably.
“Compression” is when the shock gets shorter; “rebound” is when the shock gets longer. For example, when the front bumper is depressed, compression occurs, when it is released, the shocks rebound.

Monotube Vs. Twintube

• Monotube shocks are also incorrectly known as gas shocks. Both monotube and twin tube shocks use gas pressure. Monotube shocks use high pressure gas (nitrogen) on the opposite side of a floating piston to keep a constant pressure and volume of oil in the shock body as the shaft adds and subtracts volume when the shock oscillates. Twin tube shocks use a lower pressure gas in a bag to achieve the same result.

  

• Monotube shocks have an advantage of control, since their larger pistons displace more oil for a given stroke. This is especially true for the rebound stroke. The greater the amount of oil moving through a shock's piston, the easier it becomes to regulate the flow and thus control the dampening forces of the shock. Although fading is generally not a problem for micro sprints, monotube shocks also will not fade due to heat. They stay cooler because the piston and oil are in direct contact with the outside wall of the cylinder allowing for better dissipation of heat. Monotube shocks also last longer because they have less moving parts to wear out.
• Twin tube shocks use a rupture-prone gas bag to hold the nitrogen. When this bag breaks the nitrogen mixes with the oil making the shock skip as the gas moves through the piston orifices. Bubbling noise can be heard when the shock is actuated by hand. In contrast, an advantage for twin tube shocks is they can still function properly with small dents in the housing because of the use of their inner cylinder.
• Rod pressure is the amount of force that pushes the shaft of the shock out. Rod pressure is undesirable because it essentially increases spring rate. This makes the car feel like it is on top of the race track. An advantage of twin tube shocks is that they have less rod pressure due to the smaller piston and the lower gas pressure. ARS monotube shocks use a unique foot valve to virtually eliminate rod pressure, this is a huge advantage to using ARS monotubes.
• So whether you choose the high performance monotube or the economical twin tube shock, remember that it is much more important to select the correctly valved shock for your car.

Gas Pressures
The nitrogen gas pressure in a monotube shock is required at all times for it to function properly. The gas pressure can be adjusted to suit various track conditions. Changing gas pressure effects the car in a manner that is like increasing spring rate  (stiffer bar) and adding turns to that corner. You can think of it as though adding 80 psi is like going to the next stiffer bar size.

Less pressure on the right side shocks will tighten the car in the middle of the corner. Increasing the pressure in the front shocks will provide more weight transfer to the rear providing more forward bite, less pressure in the front will provide less forward bite.

Setting Gas Pressures
The pressure in the ARS monotube shocks can be adjusted from 10 psi to 100 psi. To start set the front shocks at 20 psi and the rear shocks at 10 psi.

• Back the wing nut off all the way on the inflation unit before screwing it on the Schrader valve of the shock.
• Tighten the hex nut coupler onto the valve of the shock.
• Screw the wing nut all the way clockwise so it opens up the shock valve.
• Pressurize the shock to the desired pressure using nitrogen gas only.
• Screw the wing nut counter clockwise all the way to seal the shock valve.
• Gas pressure can be heard escaping from the shock as the inflation unit is removed.
• 5 to 7 psi will be lost every time the inflation unit is applied to the shock.

ARS Shocks
ARS shocks contain the highest quality components for maximum performance. Hyper Racing is the world’s largest distributor of ARS Shocks. We work with ARS through extensive track testing to develop new and better valving combinations. This year’s line up of shocks features a new wide range adjustable compression right rear shock, the B3274.5/7-2. This is Mike’s new best friend out on the track. ARS has perfected other shock valvings to make your handling even more spot-on.

Building a Quality Shock

• ARS dynos every shock built and allows no overlap in valving numbers, maintaining the tightest tolerances in the industry.
• ARS removes all air  and pressurizes the shock properly avoiding cavitation.
• Each twintube valve is individually flow tested to ensure consistent dampening.
• The 3200 ARS series (mono tube) shock utilizes a base valve installed between the floating piston and the valving piston to isolate the pressure, allowing for substantial reduction in rod pressure. Maximum traction is obtained because pressure build up is dramatically reduced with the use of the low rod pressure. The base valve design requires so little gas pressure that certain valvings have only 3 lbs. of rod pressure. This low rod pressure creates more driver feel which is lost in many high pressure shocks. The 3200 series shock will accept gas pressure from 10 lbs. to 100 lbs. which provides for fine tuning the chassis balance with gas pressure.
• Shock Codes that end in an 'S' do not need any gas pressure to function, thanks to a secrete that I am not allowed to reveal.
• Shock Codes that end in an 'X' have a new designed valve the virtually eliminates any hysteresis. Hysteresis is the residual forces in the shock as it changes direction. The bottom line is it really helps shocks control the car on a rough track.

Shock Lab
Hyper Racing’s Shock Lab will come to the rescue! A run on the Roehrig Shock Dyno can detect malfunctioning shock(s), identify problems with chassis handling, plot rebound and compression dampening curves, and compare your shock to a standard shock of the same valving. If a problem is found, or if you just wish to revalve, we will either service the shock in-house or send it out to our partners at ARS. Click here to see the shock specs we look for when we dyno shocks.

The shock recommendations listed on the sheet below is now outdated but it can be used as a reference for those of you that do not have the new style shock valving. As of 11/2011 we came out with a whole new set of shock valving combinations that greatly improve chassis handeling, you can view the shocks here.

Here are some sample dyno sheets.