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Bilstein Shocks for the Oval Track

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Oval Track Shock Specs

There are two basic types of shock absorbers used in today's short track racing: the conventional twin-tube reservoir shocks and the mono-tube gas pressure shocks pioneered by Bilstein.

Most short track racers still race on the older style, twin-tube shocks. But if you watch closely, you'll find more of your competitors switching to the up-to-date, mono-tube gas pressure shock absorbers. Although there are other brands of mono-tube gas shocks making an appearance in America's pit areas, Bilstein technology is so far ahead and so different, that their performance cannot be equaled.

Bilstein's larger piston area produces instantaneous response to the slightest suspension movements. Dead spots in a Bilstein are an impossibility.

Deflective disc valving in Bilstein shocks eliminates the need for check valves and tiny coil springs that cause inconsistencies in shock valving. All Bilstein shocks of the same part number produce, with little variation, the same damping force. Twin-tube shocks cannot be built with as narrow a band of consistency. In other words, when you bolt on a Bilstein, you know what shock valving is in your car.

Shock absorber performance fades away when the oil in the shock cavitates (foams). Conventional twin-tube shocks that are called "gas charged" contain a small plastic bag holding a minuscule amount of gas under little pressure. This design, while low in cost to manufacture, is ineffective on the track.

Under extreme G-forces, on rough tracks and in high heat conditions, "gas charged" twin-tube shocks do not resist cavitation as effectively as mono-tube gas pressure shock absorbers. This is the reason that all Winston Cup, Indy Car, Formula One and Off-Road racers long ago discarded twin-tube shocks in favor of mono-tube gas pressure technology.

Why Race on Bilstein Shocks?
  1. Because the valvings are consistent, your set-ups will be more precise. You will know what is on your car.
  2. Bilstein's larger piston and deflective disc valving develops control force when you need it, at the slightest movement of the suspension. You'll get weight transfer when you need it, better control under braking and your tires will stay on the track through the rough spots.
  3. Bilsteins do not fade. Your chassis will handle as good at the end of the race as it did at the start.
  4. Bilsteins are rugged. They last for years and are rebuildable and revalvable.
  5. When the advantages of Bilstein gas pressure shocks are tallied up, you will have spent less money on shock absorbers and collected more money at the pay window.

Bilstein's patented deflective disc valving system allows for exact valving of both compression and rebound movements.

Answering the Racer's Questions
The following are some commonly asked questions and their corresponding answers concerning Bilstein gas pressure shocks:

Q. Why is the shaft on a Bilstein shock always extended?
A. As mono-tube gas shocks, Bilsteins are under gas pressure to deliver the most responsive valving for ultimate control. This pressure, called the gas reactive force, and Bilstein's perfect internal seals force the shaft to be extended.

Q. Is the car more difficult to scale with Bilsteins?
A. Bilstein shocks have no effect on the results as you weigh the four corners. The gas reactive force in Bilstein shocks may raise your car's ride height slightly. Simply adjust the chassis downward to the desired ride height.

Q. Does Bilstein offer specific applications for the various dirt and asphalt racing series?
A. As the set-up charts in the catalog indicate, Bilstein has shocks valved specifically for both dirt and asphalt surfaces of various track lengths.

Q. Are Bilstein difficult to understand and use?
A. After reviewing the various set-ups in this catalog, you'll be ready to select the proper shocks for your specific race car. Bilstein valving is precise. Once you purchase your Bilsteins you can be certain that they will perform at peak efficiency throughout their long life.

Q. Why should I spend the extra money on Bilsteins when I can buy twin-tube shocks for less.
A. As we point out in this catalog, Bilstein shocks are fabricated from the highest quality components for long life performance. Typically Bilsteins are only slightly higher than twin-tube brands. Since they will far outlast conventional shocks, they cost much less over the long run. Bilstein shocks are the least expensive way to lower you lap times.

Q. The companies that sell only twin-tube (low pressure gas) shocks say their design outperforms mono-tube (high pressure gas) shocks. How can I know the truth?
A. Take a trip to a local discount department store that sells replacement shocks for cars and trucks that drive on the street. You'll find shocks priced from about $8.99 to $29.99. All of the shocks on display will be twin-tube shocks. Their price reflects the fact that twin-tube technology is relatively unsophisticated and very low cost to produce. At a new car dealership you'll find that low cost base line cars and trucks are factory equipped with twin-tube shocks that add little to the cost of the vehicle. Factory installed Bilsteins can also be found on Mercedes Benz, Ferrari, Porsche, Chevrolet, Z-71 trucks and many other high performance vehicles from around the world. World class automotive engineers wouldn't consider equipping any high performance vehicle with twin-tube shocks. Finally, take a stroll through the pit area at a NASCAR Winston Cup, Busch, Craftsman Truck, CART, IRL, IMSA, or Formula One race and you'll find not a twin-tube shock in sight! By searching out the facts, you will know the truth; and the truth will make you fast!

Shock Valving Nature

The amount of damping force produced by any shock absorber, twin-tube or mono-tube, is dependent upon the speed at which the shock's piston is traveling when the damping force is measured. Therefore, the velocity that your race car's suspension travels vertically determines the piston speed inside the shock. The faster the piston is forced through the shock's reservoir of oil, the stiffer the shock becomes on both the compression and rebound strokes.

A shock dyno cycles the shock absorber through a wide range of piston speeds (called "shaft velocity" in the industry). The amount of damping force developed is measured along a series of increments in mm/sec or inches/sec.

How to Shock Tune Your Chassis

Study the current Bilstein set-up recommendations for your particular type of racing. These combinations are tested and proven successful, but due to many variables that come into play under racing conditions, it is to your advantage to have a basic understanding of how shock damping rates affect your lap times. Adjustments can then be made with reasoning and understanding.

Simply stated, shock absorbers convert the kinetic energy of the spring movements into heat. This heat is then dissipated into the air through the shock tube or body. In practical application, shock absorbers are necessary to maintain maximum tire patch contact to the track as the car corners and negotiates irregularities on the racing surface.

Spring rates determine how far your chassis rolls, pitches or squats. Shock rates determine the length of time it takes for each of these movements to occur.

Rebound damping controls the movement of that part of the car's sprung mass that is stored in a compressed spring. The rebound damping rate determines how long it takes for the compressed spring to return to static ride height. The larger the rebound figure, the more the shock resists the compressed spring's effort to rebound, and the longer it takes for the chassis to return to the static ride height.

Compression damping controls only the oscillation of the car's unsprung weight. Therefore, it is normal to use less compression damping than rebound damping. The exception occurs when we choose to slow the downward movement on a particular corner of the car to mimic the effect of a stiffer spring.

Trouble Shooting the Car on the Track
If your car is:

Loose (Oversteer) from 0 to 90
Increase compression rate on front.
Decrease rebound rate on rear, or only on the left rear.

Tight (Understeer) from 0 to 90
Decrease compression rate on front, or only right front
Increase rebound rate on rear, or only on the left rear.

Loose (Oversteer) from 90 to 0
Decrease rebound rate on front.
Decrease compression rate on rear, or only on right rear.

Tight (Understeer) from 90 to 0
Increase rebound rate on front.
Increase compression rate on rear, or only on right rear.

When analyzing corner entry, or deceleration handling, realize that the chassis is affected by:

Compression rate in front
Rebound rate in rear

When analyzing corner exit, or acceleration handling, realize that the chassis is affected by:

Rebound rate in front
Compression rate in rear

Bilstein shocks are famous for their superior performance on very rough asphalt or rutted dirt tracks. You may need to choose a shock with more compression damping than found on our set-up sheets under extreme rough track conditions. We have included this section in our catalog to broaden your understanding of the function of shock absorbers and to show you the effect they have on handling.

Keep in mind that there are many adjustments on your chassis other than shock absorbers. The oversteer/understeer balance may be affected by stagger, tire compound, wheel spacing, spring rates, sway bar, panhard and others. Shocks can be used to fine tune your chassis to gain that last few tenths of a second on the track.

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The majority of the information on these pages has been copied from the Bilstein.com website and is the property of Krupp Bilstein of America. 1999-2002 All rights reserved.
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