Reference: Suspension Information

[iamgod]

"Lean Less

The inside scoop on anti-roll bars

story by john comesky

Any enthusiast worth his salt knows that ires have arguably the biggest impact on a vehicle's handling. Obviously, however, there are chassis dynamics that extend beyond the realm of tires. Once you increase the traction threshold at the road surface, then you may be ready to take the next step into improved vehicle handling: reducing body roll through the use of anti-roll bars.
Properly chosen (and installed), anti-roll bars will reduce body roll, which in turns leads to better handling, increased driver confidence and, ultimately, lower lap times.



What Is Body Roll?
Chances are, you've experienced the effects of body roll every time you're behind the wheel. It happens during almost every turn when one side of the car lifts, causing the entire vehicle to lean toward the outside of the turn.
The cause of body roll is simple physics: An object in motion tends to stay in motion until acted upon by an outside force. So in practical terms, as you drive ahead in a straight line, you're allowing a couple of thousand pounds of vehicle, fluids and passengers to build momentum in that straight line.
When you tell everything to change direction suddenly, through input at the steering wheel, the front tires may change direction thanks to the mechanical advantages of the steering system, but the momentum of the vehicle, fluids and passengers continues in the original direction. The tires are the only element capable of generating an outside force that can act against this momentum and change its direction.
At this point, one of two scenarios is most likely to occur. If enough momentum exists in the original direction, and the tires lack enough grip to act against the original forward energy, then the vehicle will slide out of the turn as the tires lose traction. However, if the tires have enough grip at the road surface, then instead of sliding, the vehicle's traction at the road surface will overwhelm the original forward momentum and act upon the original forces to induce a change of direction. Hence, a cornering maneuver.
But what happens to that energy? Even though we may have had enough grip to hang on through the turn, we know that the momentum of the vehicle mass will continue in the original direction. The result is a weight transfer toward the new outside edge of the vehicle-the same direction as the original forward momentum.
If enough energy is behind the weight transfer, then this energy will cause the outside suspension (in this case, the spring and strut assembly) to compress while the other side lifts and extends. An engineer type likes to describe this by saying that one side moves into jounce while the other moves into rebound. The rest of us call it lean or body roll.



Why Is Body Roll a Bad Thing?
We often hear that preventing body roll is "so important" that we must all rush out and buy this product or that product in order to prevent it. And many enthusiasts have consequently accepted that body roll is therefore bad. But what exactly does body roll do to negatively affect vehicle handling?
For starters, it disrupts the driver. This is probably the effect that most drivers can see and feel during their own driving experiences. And while this is not the most important negative effect of body roll, it is true that the car does not drive itself-no matter how many aftermarket parts you install. So keeping the driver settled, focused and able to concentrate on the task of driving is a foremost priority for spirited vehicle handling.
However, the most often misunderstood effect of body roll upon vehicle handling is the effect of body roll upon camber-and the effect of camber changes upon tire traction.
Put simply, the larger the contact patch of the tire, the more traction exists against the road surface, holding all else constant. But when the vehicle begins to lean or roll to one side, the tires are also forced to lean or roll to one side.
This can be described as a camber change in which the outside tire experiences increased positive camber (rolls to the outside edge of the tire) and the inside tire experiences increased negative camber (rolls to the inside edge of the tire.) So a tire that originally enjoyed a complete and flat contact patch prior to body roll must operate on only the tire edge during body roll.
The resulting loss of traction can allow the tires to more easily give way to the forces of weight transfer to the outside edge of the vehicle. When this happens, the vehicle slides sideways-which is generally a bad thing.



How to Prevent Body Roll
By definition, body roll only occurs when one side of the suspension is compressed (moves into jounce), while the other extends (moves into rebound). Therefore, we can limit body roll by making it harder for the driver-side and passenger-side suspensions to move in opposite directions.
One fairly obvious method to achieve this is through the use of stiffer springs. After all, a stiffer spring will compress less than a softer spring when subjected to an equal amount of force. And less compression of the suspension on the outside edge will result in less body roll.
However, stiffer springs require the use of stronger dampers (struts or shock absorbers) and have an immediate and substantial effect on ride quality. So, even though handling is improved, they may not be the easiest or most cost-effective way to achieve the objective of reducing body roll.
For many enthusiasts, the use of anti-roll bars-also known as anti-sway bars, roll bars, stabilizer bars or sway bars-provides a more cost-effective reduction in body roll with minimal negative impacts upon ride quality.



How an Anti-Roll Bar Works
Put simply, an anti-roll bar is a U-shaped metal bar that links both wheels on the same axle to the chassis. Essentially, the ends of the bar are connected to the suspension while the center of the bar is connected to the body of the car.
In order for body roll to occur, the suspension on the outside edge of the car must compress while the suspension on the inside edge simultaneously extends. However, since the anti-roll bar is attached to both wheels, such movement is only possible if the metal bar is allowed to twist. (One side of the bar must twist upward while the other twists downward.) So the bar's torsional stiffness-or resistance to twist-determines its ability to reduce body roll. Less twisting of the bar results in less movement into jounce and rebound by the opposite ends of the suspension-which results in less body roll."

 

[iamgod]

"Factors that Determine Stiffness
There are two primary factors that determine an anti-roll bar's torsional stiffness: the diameter of the bar and the length of the bar's moment arm. Diameter is generally the easiest concept to grasp, as it is somewhat intuitive that a larger diameter bar would have greater torsional rigidity.
Torsional (or twisting) motion of the bar is actually governed by the equation: twist = (2 x torque x length)/(p x diam4 x material modulus.) And since the diameter is in the denominator, as diameter gets larger, the amount of twist gets smaller. Which, in a nutshell, means that torsional rigidity is a function of the diameter to the fourth power. This is why a very small increase in diameter makes a large increase in torsional rigidity.
For example, to compare the rigidity of a stock 15mm bar to an aftermarket, 16.5mm one, simply use the equation 16.54/154. Some quick math yields the figure of 1.46. In other words, a 16.5mm bar is 1.46 times as stiff-or 46 percent stiffer-than a 15mm bar of the same design.
Add just one more millimeter to the diameter of the bar-for a total of 17.5mm-and the torsional strength skyrockets to 85 percent stiffer than the stock 15mm bar (17.54/15.04 = 1.85).
However, in addition to the diameter of a bar, there is another very important factor that determines an anti-roll bar's torsional rigidity. This factor is known as the length of the moment arm-or in common terms, the amount of leverage between the vehicle and the bar.
As with anything, an increased amount of leverage makes it easier to do work. This is governed by the lever law: force x distance = torque. As distance-or the length of the lever-increases, the resulting amount of torque also increases. (This is why it was easier to move your big brother on the teeter-totter when he moved towards the middle and you stayed out on the end. You enjoyed increased leverage at the end, while he suffered from reduced leverage near the middle.)
Because an anti-roll bar is shaped as a "U," the ends of the bar that lead from the center of the bar to the end-link attachment serve as a lever. As the distance from the straight part of the bar to the attachment at the end link becomes longer, the torque applied against the bar increases-making it easier for a given amount of energy to twist the anti-roll bar. As this distance is reduced, torque is reduced-making it more difficult for a given amount of energy to twist the anti-roll bar.
It is this lever law that is applied during the design of an adjustable anti-roll bar. By using multiple end link locations, the distance from the point of attachment to the straight part of the bar can be altered. Or, in engineers' terms, the length of the moment arm can be increased or reduced in order to make more or less torque against the bar.
Using a setting farther from the center of the bar increases the length of the moment arm, resulting in more torque against the bar, allowing more twisting motion of the bar, creating more body roll. Using a setting closer to the center of the bar reduces the length of the moment arm, resulting in less torque against the bar, allowing less twisting motion of the bar, creating less body roll.
The actual impact upon torque can be compared by dividing the center-to-center distances of the end-link attachment points. For example, say the center-to-center distance of the stock rear anti-roll bar is 200mm. We can compare this to the 160mm distance of the firmest setting of a four-way adjustable 17.5mm bar by simply dividing the distances (160/200 = .8). In other words, a 160mm center-to-center bar produces only 80-percent of the torque that would be produced by a 200mm center-to-center bar of the same diameter. Or simpler yet, by using the 160mm end-link attachment points, we increase the stiffness of the anti-roll bar by an extra 20 percent.





What the Heck Is TLLTD?
TLLTD stands for Tire Lateral Load Transfer Distribution. While this term may sound complex, it simply measures the front-to-rear balance of how lateral load is transferred in a cornering maneuver. It is commonly used to compare the rate of lateral traction loss between the front and rear tires.
Put simply, there is only so much force that a tire can handle. When we ask more of the tire than the tire can deliver, it "saturates," or loses traction. If the front tires saturate before the rear tires, then we call this understeer or push-which means that the car tends to continue moving in the original direction, even though the wheels are turned.
If the rear tires saturate before the front tires, then we call this oversteer or loose-which means that the rear of the car tends to swing around faster than the front, causing a spin. When neither of these conditions prevail consistently, then we describe the chassis as balanced.
We can measure and compare the steady-state understeer and oversteer characteristics of a vehicle by assigning a lateral load transfer percentage of the front relative to the rear. A TLLTD value equal to 50 percent indicates that the chassis is balanced-or both the front and rear tires tend to lose traction at roughly the same time. A front TLLTD value greater than 50 percent indicates that the front tires lose traction more quickly than the rear tires-resulting in understeer. And a front TLLTD value lower than 50 percent indicates that the rear tires tend to lose traction more quickly than the front-resulting in oversteer.
It is important to note that our discussion of TLLTD only considers steady-state cornering maneuvers, such as a long 270-degree on-ramp or off-ramp. Moderate-to-aggressive throttle or brake application can upset this balance during a transient condition, briefly transitioning a vehicle from understeer to oversteer."

 

[iamgod]

The Effect of Anti-Roll Bars Upon TLLTD
Ideally, you now understand how an anti-roll bar can be used to limit body roll, and you understand that reduced body roll can lead to a reduction in adverse camber changes for better tire traction. But what may not be obvious is the effect of anti-roll bar changes upon TLLTD (understeer and oversteer.)
In fact, given the above information, one might even assume that a firmer anti-roll bar, which leads to better camber control, would lead to better traction. If we add a firmer anti-roll bar to the front, traction loss diminishes, so understeer is reduced, right?
Wrong. Let's evaluate more closely the meaning of TLLTD-tire lateral load transfer distribution. Stated another way, we might describe TLLTD as the relative demand of side-to-side energy control that is placed upon the tires. Because a firmer anti-roll bar allows less deflection, it will transfer side-to-side energy (lateral loads) at a faster rate.
As the rate of lateral load transfer increases, additional demands are placed upon the tire. So if we install a firmer anti-roll bar in the front, then we increase the distribution of lateral load transfer toward the front tires. This increases the front TLLTD value, which will result in additional understeer, holding all else constant.
The same logic also holds true in the rear. A firmer anti-roll bar in the rear will increase the rate of lateral load transfer, placing more demand upon the rear tires, accelerating lateral traction loss and creating more oversteer, holding all else constant.
This is why blindly adding parts to your car may not produce the desired results. A wise consumer consults with-and buys from-knowledgeable experts that have the tools to make informed tuning recommendations.



I Want a 50 Percent TLLTD On My Car, Right?
Since on paper a 50-percent TLLTD indicates a balanced chassis, many enthusiasts are tempted to jump to the conclusion that this is therefore desirable. They may think that all cars should obviously come this way from the factory. Unfortunately, this is not the case-and the considerations are not that simple.
In reality, a car with a 50-percent TLLTD is literally on the constant brink of oversteer. And there are many factors that can quickly and easily take the car from the brink into a full-scale, out-of-control, spinning-in-circles disaster.
For starters, consider the effects of weather conditions that might create a wet or icy road surface. Or imagine that the driver happens to apply too much brake late into a turn-a common mistake among novice drivers. Or consider the effects of varying tire temperatures, tire pressures, or tire wear-all of which will have major impacts upon lateral traction thresholds. And of course, varying weight distribution, as a result of changing fuel tank levels, passengers, or the number of subwoofers in the trunk, will also impact TLLTD.
With all of these things to consider, automotive design engineers are forced to create a more conservative TLLTD. As a result, they intentionally target higher front TLLTD values so that stock vehicles will be prone to understeer-the assumption being that understeer is safer and more predictable for the average driver.
For example, a stock DOHC Saturn is tuned to produce a front TLLTD of approximately 63.4 percent-a relatively conservative target. (But give Saturn some credit, as this is on the aggressive end of the conservative spectrum, especially compared to other front-wheel-drive economy cars.)
As a general rule, an average street-driving enthusiast is probably willing to accept some compromises-within reason-of a more aggressive TLLTD in exchange for better handling. A suitable target is probably a front TLLTD value of approximately 58 percent, a value that is considered aggressive, but suitable for street driving.



How do I Create the Right Handling Balance?
Since most enthusiasts do not have the knowledge or software needed to calculate chassis characteristics such as TLLTD, the responsibility falls upon knowledgeable tuners.
Obviously, TLLTD and body roll will both be affected by changes to springs and anti-roll bars. While understanding the effects of multiple changes can get confusing, the answer is usually only a phone call away.



John Comesky is the owner of SPS, the largest Saturn tuning company in the U.S. SPS covers all aspects of Saturn performance: engine, suspension, brakes and wheels and tires. They can be reached by phone at (937) 296-1417, and their Web page may be viewed at www.spswebpage.com. "

http://www.grassrootsmotorsports.com/swaybars.html

 

[iamgod]

"Repent

story by don alexander-illustration by ruben cueto

Picture this: At the race track, you're unloaded and ready to go for the first practice session. After the session is over, you feel lost because your car's handling is way off. You make changes that should help, but in the next session, the car feels even worse. The same scenario continues for the remainder of the event, and you're very unhappy with the result.
There is a good chance that one or more of the following chassis tuning sins is the culprit behind your situation. Any one of these problems can be your undoing; most racers are guilty of breaking several of the rules regularly. Here's a primer to help you spot-and correct-these most common causes of bad handling. May you find salvation at the checkered flag.

Thou Shalt Have a Solid Baseline
One key to being fast and competitive is repeatability-and you cannot repeat results if you do not know where you started. That's why you need a good chassis baseline. You can start with the baseline settings recommended by your chassis builder or suspension guy. If you have the experience, however, you can create your own. And best of all, if you have records from previous outings at the track you are headed to, you'll have a head start.
You should at least record the following: frame heights, crossweight percentage, rear and left-side weight percentages, all four tire circumferences, fuel load, gear ratio, wing settings, spring rates (bar neutralized), shock valving, toe, alignment, pinion angle, Panhard bar height or Watt's linkage settings, and any other settings than can affect the handling.

Thou Shalt Not Prepareth at the Track
This happens too often. You run out of time or have inadequate help before a test or race, so you end up preparing the car at the track-or at least finishing the job there.
It is very difficult to create a good setup at the track; you can do a much better job at the shop. And track time is expensive for a test day; wasting that time playing in the pits is not effective. If you're prepping your car at the track during a race weekend, forget any chance of a good result.

Thou Will Taketh Tire Temperatures
Tire temperatures are your link to what goes on between the tire contact patch and the track surface. I find it difficult to make sound tuning decisions without tire temps. Tire temperatures should be taken religiously every time the car comes off the track-even after a race.

Thou Will Take Segment Times
Time around the track is gained in very small increments. Chassis adjustments can make a car faster (or slower) around the track, but may cost time in certain areas of the race track. Knowing this can add to the data available for you to make sound tuning choices.
The only way to accomplish this is to record times in several segments of the race track. (For example, timing how long it takes to get through a series of corners.) You don't need to take times in every segment on every lap, but taking segments at various points for each session will prove very valuable, especially in testing."

 

[iamgod]

"Thou Shalt Not Have Excessive Crossweight
Crossweight, the measure of right front and left rear combined weight versus total car weight (both with driver), is a useful tuning tool. In road racing or autocrossing situations, excessive crossweight will help handling in one direction but hurt in the other-and it hurts more one way than it helps the other way. Crossweight should be set at 50 percent, if possible, and never less than 49.5 percent or more than 50.5 percent.

Thou Shalt Keepeth Thine Records
This may be the most costly sin of all. There is just too much data to track if you don't write everything down in an organized way. Even if you luck into a good setup, without records you will be unable to repeat it without going through the complete process all over again.
The best time to record notes is back in the shop after a race. If you have a good race setup, these notes will tell you how to get back to it the next time you race at that track under similar circumstances. And if the results were not so good, at least you know you need to do something different.

Thou Shalt Not Listen to Too Much Advice
Everyone is a setup expert, or so most people would have you believe. If you want to be successful, then you must learn enough to make your own tuning decisions within your own team. Listening to advice from others is one thing, but putting it to use is another.
Even if the person offering advice is very knowledgeable, that person likely does not know your situation, preferences, resources or needs. Most often, the person offering advice is less knowledgeable than you are, and usually only knows a couple of things that could cure your perceived problem.

Thou Will Haveth a Game Plan
Any plan is better than no plan at all. Take the time to create a game plan for each race, beginning with your realistic objectives, maintenance schedules, testing and race strategy. Remember that part of a good game plan is the flexibility to alter the plan as needed. Usually, no plan equals no result.

Thou Shall Determineth the Exact Problem
A handling problem can occur anywhere on the track. Is it corner entry, mid-turn or corner exit? Does it happen everywhere? If a problem occurs in one place, does it result in a different problem someplace else?
The classic example of this situation is corner-entry understeer that a driver over-compensates for at the exit of the corner, creating an oversteer condition. The driver says the car is oversteering, but the real problem is the corner-entry push. Adjusting for the oversteer will make the problem worse.

Thou Shalt Not Have a Suspension Bind
Suspension binds create an inconsistent handling situation. If a bind is present, it is just about impossible to properly tune the suspension. If the car does not respond the way you think it should to suspension changes, check for bind in the suspension. Checking for binds should be part of your routine setup process.

Thou Shalt Not Have a Dead Shock
A bad shock can be very difficult to feel. Check the shocks if you cannot get the chassis tuned effectively. Feel for a dead spot or lack of resistance in both rebound and compression.

Thou Will Set Thine Car up According to Driver Experience
Often, the fastest setup for a given car is too aggressive for a driver without some experience. When the suspension is too stiff, especially the shock valving, it is difficult for the driver to feel what the chassis is doing. The car reacts too quickly for the driver to sense what is occurring.
Softer springs and shocks, while slower for the experienced driver, may be faster for the inexperienced driver.

Thou Shalt Not Make Corner Weight Adjustments at Only One Corner
To adjust corner weight percentage, you must change frame height. Suspension geometry is designed to work best at a certain frame height, and changing the frame height can alter the suspension geometry in a negative manner.
Making one big change at one corner can cause this problem to happen. The trick is to make small changes at all four corners. Instead of putting a turn in the right front, put a quarter-turn in the right front and left rear, and take a quarter-turn out of the left front and right rear.

Thou Shalt Not Try to Cure Handling Problems With Only One Element
Any handling problem can be changed by adjusting several different parts on a car; it is ineffective to change only one or two items to improve the handling. Often engineers, whether their specialty be shocks, tires, springs, or whatever, will try to cure a problem by using what they know best.
This is often not the most effective way to solve a problem. It is important to look at the entire system as a whole, then make changes that suit the system best and offer the most favorable compromise.

Thou Shalt Not Make More Than One Change at a Time
While more than one suspension adjustment may be needed to cure a handling problem, it is always best to make only one change at a time. Make a change, and then go test.
Making more than one change at a time can produce results that are difficult to analyze. Which change helped, and did one change actually hurt?

Thou Shalt Not Stray from Recommended Frame Heights
This can cause binding in the suspension or, at a minimum, cause undesirable suspension geometry. Don't stray too far from home.

Thou Shall Measure Accurately
Recording inaccurate measurements is as bad as not keeping records in the first place. This can lead to all kinds of problems.

Thou Will Carry a Consistent Fuel Load
Changing fuel load will always be a setup and tuning problem. As fuel is burned off, handling will change as the weight in your fuel cell changes. If you do not tune with a constant fuel load, your data will be inaccurate and the results misleading. No more than a two-gallon fluctuation is acceptable. One gallon is a better mark. Remember that each gallon of gas weighs about seven pounds.

Thou Will Establish Good Crew/Driver Communication
If the crew and/or driver are not sure of the concepts of tuning and are not clear about the language, all sorts of problems can occur. Everyone on the team needs to be on the same page.

Thou Will Control Over-driving
If a driver is over-driving the track or car setup, most of the data, whether from the driver or tire temperatures, will be less than accurate. Over-driving not only abuses the tires, but also masks real handling problems.

Thou Shalt Not Make Changes Which are too Big
If a change is too big, it can cause handling problems that are worse than the ones you already have. On the other hand, a change too small can be difficult to detect by the driver or on the stopwatch. Big changes include altering more than two numbers on shock valving, more than 15 percent in spring or bar rate, more than two percent crossweight or more than a 1/4-inch change in ride height.

Thou Must Understand the Whole System
Understanding the whole system is very important. The key is to understand how any change affects the tire contact load and traction. Always thinking in terms of tire contact patch load and traction will help you focus on making the best change possible for the situation.

Thou Must Recognize Changing Track Conditions
Track conditions constantly change. The car may get faster during the day even though the lap times are slower, because the track may be slowing more quickly than the car is getting faster. If in doubt, return to the starting setup to see how the track has changed.

Thou Will Not Chase Old Tires
At some point, tires get too hard to be fast. There is a point beyond which, no matter what you do, the car will not get faster. Chasing an old set of tires is ineffective.





About the Illustrator
Ruben Cueto is an illustrator with a unique style and a diverse clientele. After graduating from Long Beach State University, he has gone on to do artwork for Forbes, Information Week, NEA Today, and the Los Angeles Times. Mr. Cueto's portfolio is online and can be viewed at http://home/earthlink.net/~rubenc49 with an email link at the site. "

http://www.grassrootsmotorsports.com/repent.html

 

[iamgod]

"Shocking Behavior

If you knew the extent of the effects that shocks have on handling, you'd be... well... shocked.

story by david s. wallens -- photos as credited

Given enough time, most enthusiasts can figure out how an anti-roll bar or a set of trick brake pads will increase their car's performance, but how many out there truly understand the benefits of a good set of shock absorbers? Probably too few, which is unfortunate. Properly selected and tuned, shocks can make or break a car's foundation.
If you're one of the masses who believe that a stiffer shock is always the right way to increase performance and decrease lap times, then read on.
"Perceived stiffness cannot be better by definition," explains Jay Morris, owner of the racing shock company Advance Design and parent company Ground Control. "Perceived stiffness would be a misconception compared to actual stiffness, which should benefit the race car.
"Why the distinction? Because there is such thing as a perceived stiffness that is not actually stiff. This is found in a shock that is a poor design with internal leakage preventing any real handling benefit, but which is very stiff over bumps in a misguided attempt to improve handling. The driver feels the bumps more, but the chassis is still uncontrolled. This is usually the very worst handling setup for any car."

What Do Shock Absorbers Do?
Thanks to their common name, most people think that shock absorbers absorb the shocks and bumps experienced by the car as it travels down the road. Technically, this is not true.
In reality, the springs carry the load of the car and regulate the suspension's reaction to any bumps or dips in the road. They're the ones that really absorb the shocks. The shock absorbers time the springs' reaction by changing kinetic energy (the spring moving up and down) into thermal energy (the heat built up as the shock's oil passes through the various pistons and valves).
"Springs hold the car," explains Lex Carson of JRZ Suspension Systems. "Shocks control the spring loading and unloading."
Since the shocks are damping the springs, technically shock absorbers should be called dampers. However, we'll stick with the name shocks or shock absorbers, out of a matter of habit. A strut is basically a shock that is also a load-bearing member, but once again we'll stick with the catch-all name of shocks.
To understand how a shock works, picture a car driving down a road that is perfectly flat except for one speed bump. If the car simply has springs but no shocks, once the car passes over the speed bump, the springs will continue to oscillate until they disperse all of the kinetic energy they gained by compressing. As a result, the car will pitch and buck as it drives away from the speed bump.
Now picture a car with both springs and shocks encountering the same speed bump. The springs would once again absorb the bump, but this time the shock absorbers would damp the spring's oscillations (by converting the kinetic energy into heat), allowing the car to calmly drive away from the bump.
Unfortunately, we all live in a world filled with more than one bump. Our cars are constantly encountering all sorts of bumps and dips. Throw in a few turns and place the car in a competitive or sporting environment, and you can see how your suspension is trying to do many things at once. This is why a good set of shocks can make the difference.

Defining Our Terms
Like anything in life, there is a certain lingo used when talking about shocks-words like bump, compression, rebound and extension. These words describe the valving or action of the shock.
Bump (or compression) is when the shock rod is compressed into the shock body. Rebound (or extension) is when that rod is extended from the shock body.
Note that the same shock can have different bump and rebound characteristics. You can have a shock that has a slow bump (hard to compress) but a fast rebound (easy to extend). Matching the bump and rebound characteristics of a shock absorber to your car and venue is the trick. Hopefully, we can help you here.

Who Needs Good Shocks?
"Good shocks are probably the second most significant handling change you can make to a stock car," says autocross and road racing national champion Jeff Altenburg, "tires with an alignment being the most significant.
"The only car I competed in without [upgraded] shocks was my 1989 Formula 350 Firebird," he continues. "I ran one event in it at Jacksonville on an undulating lot, and it was floating like crazy. I had a set of hydraulic Konis for the next event which was the Sebring Pro Solo 1991, and the difference was night and day. I won the event and the Challenge."
While some limited-production performance cars like the Miata Sport and Camaro 1LE come from the factory with high-quality shocks, most cars are sold with only commercial-grade pieces.
"The average enthusiast needs a good set of shocks because he is an enthusiast," explains Advance Design's Jay Morris. "A difference in handling and performance will neither be discovered or cared about by a non-enthusiast, so why spend the money? This is the attitude (and usually correctly so) of the car manufacturers, so the average stock or replacement shock is engineered to be adequate, safe and inexpensive as priorities over performance.
"This begs the question of why can't a performance shock also be cheap? It is not so obvious. The primary reason is that a performance shock is both stiffer and simultaneously accurately stiffer. With the increased stiffness comes a requirement for less internal leakage, or bypass. For the non-enthusiast, internal leakage is softer and preferred.
"In an inexpensive shock, the advantageous internal leakage inherent in using cheaper parts (o-rings instead of actual piston wipers, for instance) is utilized as part of the softer damping characteristics desired in the non-enthusiast shock. This puts the base cost below any performance shock, because of the lower quality of parts reducing the need for accurate tolerances. An economist could probably work out an inverse exponential function to describe this, but let's just say that it costs a lot less."
Shocktek's Michael G. O'Callaghan further explains the problems encountered by most street cars: "Typically, when the shocks are at the end of their life cycle, the rod seal will fail (hopefully slowly) and the shock absorber fluid will leak out. The damping characteristics of these aged shocks are not good: the overall damping forces are much lower, the damping curves have changed and there may be air in the shock which may act like a spring. Bottom line: wheel hop, uncontrolled porpoising, excessive body roll. Very dangerous in a collision avoidance maneuver.
"A lot of the readers of Grassroots Motorsports might be changing the mission of a car, such as modifying the car to be more competitive in a weekend autocross, or installing stiffer springs, sways and shocks to make the car corner better on the street," he continues. "In this case, the idea of a 'good' shock is that it is very important to match the components carefully when modifying the suspension of a car.
"Not only does the shock have to control wheel motion and body sway," he further explains, "but it has an important influence in controlling the dive and squat of the car during braking and acceleration. And, of course, making sure that the shocks remain functional is an important preventative maintenance function that car owners should perform on a regular basis."
Enthusiasts who lower their cars-whether for looks or performance-also need to consider upgraded shocks. In most cases, the stock shocks will not properly operate when teamed with short, stiffer springs. "OEM equipment is not meant to be operated below stock height," explains Truechoice's Greg Calhoun. "Another thing to keep in mind is that when you lower a vehicle, travel is taken away from the unit. If there is not enough travel, the unit has the chance of bottoming out."
Those enthusiasts involved in competition also need to think about their vehicle's equipment and the effect those parts have on their lap times. "A vehicle's performance is directly related to the performance capabilities of its equipment," explains Jim Arentz, design engineer for Penske Racing Shocks. "When put to extreme conditions of a racing environment, typically the stock equipment does not provide the optimum handling package. Most road cars are equipped to handle everyday driving over a variety of road conditions.
"Racers need dampers that will outperform the stock parts in extreme driving conditions where comfort and ride aren't always a priority. The handling becomes paramount as the control of subtle variations in chassis platform movement and bump recovery can amount to a large gain in lap speed."
Charles Cadieux of Dynamic Suspensions further explains. "A properly-sprung and damped vehicle has a better chance of maximizing the tire contact patch, therefore better grip, better turn in, braking, acceleration, etc.""

 

[iamgod]

"Are My Shocks Shot?
So, how do you know when it's time for new shocks? Even if your car came with better-than-average shocks, they may be at the end of their lifespan.
"Generally when your shocks are shot, you will feel a lack of control or crispness in the suspension," says JRZ's Lex Carson. "The car may begin to bounce or float when you go over bumps or uneven pavement changes."
"First, the car will feel different on the track or on the road," continues Michael O'Callahan. "It might be different steering characteristics, different behavior over bumps or any other anomaly. Next, visually check the shocks for leaks. And finally, if you're still stumped, you can always have the shocks dynoed."
Note than sometimes you may have a spring problem and not a shock problem. "Spring problems tend to be persistent and consistent, shock problems tend to usually occur only in transitions," explains Jay Morris. "Theoretically, if you have a problem in the middle of a corner (shocks in low-influence mode) it will be springs. Virtually any other time can be shocks or springs."
Sometimes you'll need to take the shocks off the car and inspect them to determine if you have a problem. "A shock problem is easily detected usually by hand-compressing a damper off the car and comparing to another damper that seems to be working correctly," explains Penske's Jim Arentz. "The feel of the damper as it's compressed, the speed at which the shaft returns to an extended position, and the feel of the adjusters are easy hints at problem areas. For the best proof, a shock dynamometer usually can determine the source of a problem instantaneously, whether caused by system contamination, damaged parts, or an incorrectly-built damper."
Note than an on-track (or off-track) incident can also cause problems with your shocks. "If the car has been involved in an incident by hitting a wall, guardrail, or another car, then it is best to at least have the shocks looked at," explains Greg Calhoun of Truechoice. "Most times after a hit, the shock will need to be serviced depending on how heavy the hit was."

You Get What You Pay For
The first tough decision you must face is deciding how much to spend. All of us have budgets, all of us hate to lose, and all of us have to balance the two. In all types of racing, you should buy the best shocks you can afford. Inevitably, you'll second-guess yourself many times and curse yourself for not going to the next level. Hopefully you'll be able to sell some of your first mistakes to your competition.
Shock absorbers come in many sizes and styles. They also vary in price from $25 each to more than $2500 apiece. "The $100 shock doesn't have the technology or the sophistication that a $1000 shock has," explains Lex Carson. "It's like the difference between an IT car and a WSC car."
Why the big difference in prices? The high-dollar shocks have bigger shock shafts, bigger pistons and bigger valve stacks. They are also built with more care to tighter tolerances. All of this costs more to manufacture. We're not saying everyone needs to spend 10 grand on shocks, but buying the best ones you can afford is usually the smart move.
"Excluding a few glaring examples of cheap shocks intentionally disguised as good shocks, you get what you pay for," explains Advance Design's Jay Morris. "Sometimes in performance, sometimes in additional features, or if you spend enough, both."
For example, Jay points out how a $199 Bilstein Sport shock for a Camaro offers good valving and monotube quality, but no adjustment. That same $199 will also buy one Tokico Illumina, which has softer but adjustable valving. However, a true race shock for that Camaro that offers qualities found in both shocks-rebuildable valving, monotube quality and adjustable compression and rebound-can start at $399 each.
Where you buy the shocks and which company you use should also be a factor. Shock tuner Guy Ankeny of Pro Parts West says you should ask yourself the following questions: "Does the person you're purchasing shocks from know about the type of racing you do-or want to do-with the car? Does the shop have references for the types of shocks or shock work that they're trying to sell? Can the person selling you shocks give you any assistance in chassis setup?"
Shocktek's Michael G. O'Callaghan also notes that customer service should be strongly considered when buying shocks. "Can you get decent product support?" he asks. "Even the name-brand manufacturers can get you lost in a maze of phone tag to get even the simplest question answered."
Danny Criss from Leda Suspension also recommends looking at the quality of components and recommendations from other customers. "Serviceability and initial cost play a role as well," he explains. "Customers should be careful when comparing different manufacturers' shocks and struts to ensure that they are comparing apples with apples. A good question that customers should ask themselves is, 'What kind of performance do I want, and what is the budget?'"
Michael O'Callaghan also warns against purchasing low-quality shocks. "Bargain performance shocks can be very inconsistent in their damping characteristics which you'll be able to feel very easily," he says. "Brand name means nothing. Some of the poorest-quality shocks are made by the biggest brands, simply because their shocks are low priced. In fact, some of the very expensive shocks have pretty poor quality."
In response to the recent import performance boom, many new shock companies have sprung up on the scene. Some are truly geared towards the performance enthusiast, while others are better suited for common street use.
"When buying shocks, especially lately, reputation is more important than hype," explains Jay Morris. "Many companies have become aware of the demand for quality suspension components and have thrown their hats into the ring with hastily-developed shocks.
"Paradoxically, high-quality companies are left at the bus stop regarding new customer perception (Bilstein). Even then, there are so many inexperienced 'experts' in the Internet chat rooms that a lot of misinformation is being repeated as gospel. Try to get an opinion from someone who has owned more than one shock.""

 

[iamgod]

"Options and Choices
Besides quality and reputation, there are some nuts-and-bolts options to consider that are well-suited for the enthusiast. The ability to externally modify damping characteristics is a desirable feature. If you can easily tune your shocks to compensate for tire wear, poor surface adhesion and sometimes even poor driving, you'll be ahead of the game. Note than some shocks can only have their rebound adjusted (single-adjustable shocks), while some can have both rebound and compression adjusted (double-adjustable shocks).
"Double-adjustable shocks are geared to the serious enthusiast who requires specific ride/handling capability," explains Leda's Danny Criss. "The single-adjustable units are simple and easy to adjust and more than adequate for the average guy."
As a driver moves up the ladder, then maybe double-adjustable shocks should be considered. "At some point in a driver's career, independently double-adjustable shocks may be appropriate," says Michael O'Callaghan. "Certainly in purpose-built race cars at the higher levels, double- or even triple-adjustable shocks are appropriate. However, they are always more expensive and sometimes a lot more expensive.
"From my observations, the average guy at an SCCA event would not gain a significant advantage from independently double-adjustable shocks. Those who have them usually change the settings in the same direction at the same time. (When they stiffen the rebound, they also stiffen the compression.) This method of adjustment can be done much more cheaply by a single adjustment, double-acting shock or strut, in which the rebound and compression are changed by the same percentage by a single adjustment.
"Shocktek sells both single- and double-adjustable shocks and struts (based on Bilstein components), and the singles outsell the doubles by a wide margin."
Penske's Jim Arentz doesn't see double-adjustable shocks as so confusing, however: "Double-adjustable shocks are easy enough to understand (basically one bump adjuster and one rebound) that the average enthusiast will be able to understand with some experience and track time."
When purchasing shocks, you should ask if they are serviceable. Shocks comes in two basic flavors: sealed and rebuildable. The rebuildable ones can be repacked and tuned for your exact needs. The sealed ones can only be thrown away when they wear out, and have no potential of ever being upgraded. Of course, the rebuildable shocks have a higher initial cost.
"Konis are a very good off-the-shelf shock, but can be a great shock when rebuilt to autocross or road race specs," explains Guy Ankeny. During this rebuilding process, changes are made to the valving so the shock is better suited for its ultimate use.
"Off-the-shelf shocks are best for the average street enthusiast," says Truechoice's Greg Calhoun. "When doing custom-valved shocks, the customer is usually racing the vehicle in some form, whether it be track events, autocross, or drag racing. When the customer is in fact racing the vehicle, Truechoice will discuss with them exactly what is being performed with the vehicle and its setup to determine the proper valving for their application.
"Custom valving can also be performed to the standard street car, depending on its setup. If the vehicle is lowered in excess of 2 - 2 1/2 inches, it may be a case where the shocks will need to be revalved and shortened. This is necessary to allow for the increased spring rates and sufficient suspension travel."
"Custom valved shocks are for the discriminating enthusiast," says Advance Design's Jay Morris. "When someone is experienced enough to tell the difference in performance and/or lap times, they should consider cost vs. benefit of custom valving; often the price is worthwhile. Some shocks are exclusively custom made, and although they cost extra initially, there is no custom charge to be paid.
"Please note that there are two types of revalving: the limited revalving used to try to use a street shock on a race car, and true revalving of a purpose-built racing shock which optimizes compression and rebound levels, rates of change and limits."
Also note than several companies can successfully convert a street shock to full-race specs, installing the appropriate guts into a street shock shell for production-based race cars.
All of these better race shocks can be rebuilt or revalved at factory-authorized facilities. Depending upon the brand of shock and work performed, rebuilding and revalving can cost $20 to $135.
Rebuildable shocks can also be freshened to like-new condition at the end of the racing season or before a major event. "Shocks should be rebuilt at least every other year to keep them tip-top," says Guy Ankeny. "Fresh oil does make a difference."
Even if the high-dollar shocks totally shatter your piggybank, you can still shop wisely. "The very least anyone can expect to pay is to find a mass-produced street shock that by coincidence or substitution has sufficient damping for racing," Jay Morris explains. "These shocks usually don't last as long, and racing voids the warranty, but the cost/benefit ratio is very favorable."

Damper Designs
There are three basic designs of shock absorbers: twin-tube hydraulic, twin-tube low-pressure gas, and monotube high-pressure gas. Each of the three has its own abilities and functions, and you will find all three in street or street-derived racing applications.
One of the most common misconceptions is that a gas shock is filled entirely with gas and no oil. In fact, all three designs use hydraulic oil-they just may have a nitrogen gas charge pressurizing the oil in the shock.
The twin-tube hydraulic, as the name implies, has two cylinders (or chambers) and no nitrogen. The inner cylinder is where the rod and piston live and work, and the outer chamber is a reservoir for oil and air. As the rod travels in and out of the inner cylinder during stroking action, it displaces oil from the inner to the outer cylinder, then draws it back inside. Although this is the oldest of the three designs, it still maintains certain benefits and has a place in performance damping.
The twin-tube low-pressure gas shock is much the same as the hydraulic, except that it has a low-pressure nitrogen charge (usually 5-15 bar/70-210 psi) in the outer chamber, instead of an air pocket. Some manufacturers seal the nitrogen in a plastic bag, while others will allow the nitrogen in solution with the oil.
The original theory behind placing the nitrogen inside was that it would put the oil reservoir under pressure and therefore raise the oil's boiling point, reducing the tendency for heat-related fading or foaming as it passed through the valves. That really isn't much of a concern today as the quality of oil has increased in performance dampers. Plus, modern performance shock design has moved away from needle valves and o-ring seals that are affected by heat and viscosity changes, and most street cars and many race cars simply will not generate enough heat to challenge the oil in a proper performance shock.
However, when the nitrogen gas is in solution with the oil, it can give the added effect of damping really minute harmonics and motions that otherwise would not be big enough to make the damper's piston move.
The final design is the monotube high-pressure gas shock. The monotube's entire body serves as the chamber; this allows for a larger piston area, and therefore it has the ability to transfer more damping information over a smaller stroke area. Displacement of oil by the incoming rod is handled by a chamber at the bottom of the unit that contains a high-pressure nitrogen charge (20+ bar/ 300+ psi) and is separated from the oil by a floating piston.
Each design offers certain advantages and disadvantages, so the best choice will depend upon the intended application.
A twin-tube design, when compared to a monotube, has a longer stroke capability and greater oil volume in a similarly-sized unit. Therefore, the twin-tube will tend to give a smoother or more forgiving ride characteristic and still supply the firmness for proper handling control in vehicles that see average or long suspension stroke length.
The larger piston area of the monotube will give more control over much shorter stroke lengths or at the lowest piston speeds, but also tends to ride more harshly for exactly the same reasons. In racing applications where heat generation is more likely to be a factor, a monotube can cool itself more quickly because the shock body is the wall of the working cylinder.
You are likely to find monotubes on non-production-based race cars (formula cars and such), where control over very short strokes is mandatory and ride quality is not an issue, or on production-based race cars where once again control is more important than ride quality. Most of the rebuildable, high-end race shocks will use a monotube design.
Note that gas pressure in the shock can extend the oil's heat tolerances, but can also affect ride height because the greater pressure can act as a slight booster to the spring rate. Cars that run lower spring rates don't want the boost, so they usually use hydraulic shocks or must be willing to compensate for the gas pressure.
Monotubes can also operate while mounted on their side or at any angle, so they are more conducive to racing pushrod suspensions, while twin tubes must operate from upright to no more than 45 degrees from upright (which is still fine for most production-based suspensions)."

 

[iamgod]

"Before You Call
So let's say you have decided what vendor to go with and you have credit card in hand; now what do you do? Before calling, Danny Criss from Leda recommends you have at a minimum the following info on hand: vehicle year, model and use (street, road race, rally, autocross, etc.).
If the shocks are for a competition car, he also recommends being aware of any limitations set forth for that particular series. While the general trend in racing has been a loosening of the limits set on shocks, you're still better off knowing what you can and cannot run before making any financial commitments.
Retailers need to know the true use of the car, stresses Jay Morris. "No Walter Mittys allowed except for the Walter Mitty Challenge. No retailer likes to field complaints from customers who said they were going to go through drivers school and never did." Morris adds one more caution for prospective customers who may still be coming to grips with reality: "We also need to know how much room you have left on your credit cards."
If the car is a purpose-built car (vs. a production-based race car), there is some other info the shock builder will need, points out Penske's Jim Arentz: "Make and year of car, type of racing, inner spring diameter, spring length, needed bump travel, fully extended length of existing damper on car, number of adjustments desired, and type of chassis mounts."
From the info you provide, the shock company should be able to hook you up with the right shock. "The tuner should be able to calculate natural frequencies (or recommend spring rates) and a good guess at the damping characteristics, while on the phone," explains Shocktek's Michael O'Callahan. "Note that this information should not be a guess out of the blue, or from 'experience,' but should be based on the physics of automotive suspensions."

Rebuilding What You Have
Many of us can't afford to buy new shocks, but we would still like to improve our chances of winning. Upgrading your present shocks may be an economical way to vastly improve your car's transient handling characteristics and bump control.
For instance, if you bought off-the-shelf Konis or Bilsteins, you can have the internal valving modified so that it reacts more quickly or offers more resistance in bump or rebound. Koni shocks that initially came with only adjustable rebound can be upgraded to double-adjustable specs (both adjustable rebound and bump). Likewise, Shocktek can convert non-adjustable Bilsteins to either single- or double-adjustable specs.
This can be done at a substantial savings when compared to purchasing new shocks. At the time of the upgrade, you could also have the valving modified to suit your specific type of racing. Autocross shocks would be valved differently than road race or drag shocks.
Having your shocks upgraded is good, but just as in purchasing, be cautious. This work should be done by factory-trained personnel (who have access to a shock dyno), and hopefully by someone who also understands the type of racing you do. Look for references and look for the reputation the company has within your racing circles.



sources
Advance Design
(530) 677-8600
www.ground-control.com

Bilstein Corporation
8845 Rehco Road
San Diego, CA 92121
(619) 453-7723

Boge
3658 Atlanta Industrial Blvd. NW
Atlanta, GA 30331
(404) 699-1131

Carrera Racing Shocks
5412 New Peachtree Road
Atlanta, GA 30341
(770) 451-8811
www.carrerashocks.com

Dynamic Suspensions
85 Valleywood Drive
Markham, ON L3R 5E5
(905) 470-8778

GAB
48511 Warm Springs Blvd. #210
Fremont, CA 94539
(510) 490-7078

H&R
3815 Bakerview Spur #7
Bellingham, WA 98226
(888) 827-8881

Koni North America
1961A International Way
Hebron, KY 41048
(606) 586-4100
www.koni-na.com

Leda Suspension
13705 West 11 Mile Rd.
Oak Park, MI 48237
(248) 542-2370
www.leda.com

Neuspeed
3300 Corte Malpaso
Camarillo, CA 93012
(800) 423-3623
www.neuspeed.com

Overseas Dustributing
210 East Fourth Avenue
Vancouver, BC V5T 1G5
(800) 665-5031
www.overseas-auto.com

Penske Racing Shocks
PO Box 1056
Reading, PA 19603
(610) 375-6180
www.penskeshocks.com

Progress Group
250 Viking Avenue
Brea, CA 92821
(714) 257-0644
www.progressauto.com

Pro Parts West
21417 Ingomar Street #7
Canoga Park, CA 91304
(818) 888-8904

RD Enterprises
1300 Hill Street
El Cajon, CA 92020
(800) 683-2890
www.shox.com

Shocktek
227 Hathaway St., East
Girard, PA 16417
(814) 774-8808
shocktek@ibm.net

Truechoice
4677 Northwest Pkwy.
Hilliard, OH 43026
(800) 388-8783
www.truechoice.com

Tokico
1330 Storm Parkway
Torrance, CA 90501
(310) 534-4934 "

http://www.grassrootsmotorsports.com/shocks.html

 

[iamgod]

http://www.grassrootsmotorsports.com/cornerweight.html


corner weighting info

 

[Tay2610]

Absolutely amazing

 

[Zak8022]

god......damn.....thats alot of info.

thanks god.

 

[iamgod]

Originally posted by Zak8022
god......damn.....thats alot of info.

thanks god.

no problem............8)

 

[Zak8022]

btw..... can a mod sitcky this.... its freakin great info.

 

[Lewal]

Very informative... Ever since I got my civic I learned so much more about how cars work.

 

[iamgod]

Originally posted by Zak8022
btw..... can a mod sitcky this.... its freakin great info.

i dont think its cool enough to be a sticky

 

[Blue2k2]

wow...thats awsome...props on the post...now i have bathroom material for weeks

 

[Zak8022]

Originally posted by iamgod
i dont think its cool enough to be a sticky

eh, screw that... who cares about cool... people should read this stuff. i havent even read it all yet... but what i read was awesome, and extremely helpful.

 

[iamgod]

Originally posted by Zak8022
eh, screw that... who cares about cool... people should read this stuff. i havent even read it all yet... but what i read was awesome, and extremely helpful.

thats why its here 8)

 

[SiGSR]

Good read, very informative as well... everyone should be required to read it.