dampers and transient load transfer - The Technical Forum ...

Posted 19 August - 10:20

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Good points have been highlighted in this discussion. I would like to provide a summary and occasionally add insights.

Dampers serve multiple purposes. They manage the dissipation of energy disturbances caused by road conditions and inertia, influence the vehicle's transient response to abrupt inputs, provide the driver with feedback, and regulate the heat transmitted to the tires. Additionally, they impact variations in load on the contact patch and platform disturbances while dissipating disturbance energy. The former directly influences grip, while the latter affects aerodynamic downforce variations. Unfortunately, not all variables can be optimized simultaneously. Therefore, the optimal damper settings hinge on the specific vehicle, its tires, the driver’s preferences, and the track conditions.

Setting up dampers for a racing vehicle is a sophisticated endeavor, and it falls under the expertise of a racing engineer. The tools at their disposal include "hardware in the loop" tests, mathematical modeling, real-world track testing (on-track data collection and driver input), and, crucially, their own experience. It is important to recognize that achieving the best setup cannot be done in isolation with any single method. It’s worth noting that “single corner” assessments are generally unproductive, except in rare and unique situations. While some basic guidelines can be useful, they are often more appropriate for fine-tuning or masking persistent issues encountered during track testing. Such adjustments seldom enhance overall vehicle performance, but they can assist a driver in maximizing the existing setup.

Mathematical modeling stands out as the most flexible tool available, providing sensitivity analysis at various points during a maneuver to identify the most effective adjustments for desired outcomes. However, this modeling is generally ineffective without complementing hardware in the loop tests, which include tire evaluations, kinematics and compliance assessments, and multi-post rig tests. Among these, multi-post rig tests are perhaps the most informative, revealing significant dynamic properties and helping achieve a "generic" optimal track setup, regardless of the initial conditions (this view is admittedly subject to personal bias but is rooted in experience).

It's reasonable to assume that “optimal” overall damping coefficients can be identified for any specific vehicle, in conjunction with selected springs and tire characteristics. Their values will vary based on the properties of the vehicle and tires, as well as the definition of what’s considered optimal. The relationship between these variables is intricate, and multi-post rig assessments are among the best methods for refining overall damping coefficients. While linear dampers dissipate disturbance energy most effectively (assuming the vehicle behaves linearly), they may not fulfill all other necessary conditions.

It's noteworthy that the damping coefficient indicates the energy dissipated per cycle, while the damping style reflects the "shape" of the load-velocity trajectory, determining where energy is dissipated within a cycle. Generally, a "digressive" damping style means the damping coefficient decreases with increasing peak velocity, whereas a "progressive" style indicates the coefficient increases with higher peak velocities. There are several other damper characteristics, such as internal compliance and dependencies related to temperature, acceleration, position, and time (frequency), which I will not delve into here.

General observations about damping styles, assuming overall damping coefficients remain constant, can include:

- Shifting damping from rebound to compression phases can enhance minimum contact patch loads (thus improving grip) but may increase platform disturbance, potentially raising average ride height during on-track performance. This could permit a lower static ride height, resulting in overall performance gains.

- Excessive platform disturbance may be mitigated by introducing "blow-off" mechanisms, which limit the maximum compressive damper loads, effectively sacrificing mechanical control in favor of aerodynamic control.

- Shifting damping from compression to rebound phases could lower minimum contact patch loads (reducing grip), decrease platform disturbance, and likely lower average ride height during on-track runs. This adjustment may be advantageous in scenarios with regulated minimum static ride height requirements.

- Certain damper designs are better suited for rebound-biased settings, although contemporary 4-way adjustable dampers typically accommodate a broad spectrum of damping styles.

- Digressive damping styles on dampers linked to the steered axle may reduce steering response time, potentially introduce noticeable transient understeer, and elevate heat input to the tires.

- Conversely, a digressive damping style on dampers linked to the driven axle can hinder traction and may induce recognizable transient oversteer, likewise increasing heat input to the tires. Such transient oversteer could diminish steering input magnitude, reducing speed loss when entering high-speed corners.

- A progressive low-speed characteristic on either axle generally enhances contact patch load variations for minor inputs, but at the cost of reduced platform stability and lower tire heat input rates (which isn’t usually beneficial for slick tires).

- Additionally, employing a digressive front damper for compression and a digressive rear damper for rebound can effectively reduce vehicle pitch during braking, given that driver inputs are relatively low velocity.

- Finally, a digressive front damper rebound and a digressive rear damper compression strategy can similarly decrease vehicle pitch velocity under acceleration.

I apologize for the length of this post. I hope some of these insights will prove beneficial.

Since APEX launched these custom suspension setups centered around JRZ RS dampers, two questions have been most frequently raised by our Product Experts: "What makes these components stand out?" followed by queries about ideal spring rates, rear shock mounts, and additional accessories.

As automotive enthusiasts, our passion often centers around specific car brands, although our opinions on vehicle modifications may vary significantly. Within our close-knit team at APEX, it's evident that we appreciate cars in different ways, each with unique performance goals, perspectives, and expectations. This philosophy has guided APEX for over a decade, motivating us to offer a diverse selection of wheel fitments that meet our customers' various performance demands and budget constraints. Rigidly imposing limited “cookie cutter” wheel options on our audience would necessitate compromises, a path APEX adeptly avoided. This approach also extends to our suspension solutions in recent years.

We have carefully selected industry-leading suspension parts from three top manufacturers to create fully customizable coilover packages. With JRZ’s extensive experience in producing motorsport-grade dampers spanning over 60 years, we are confident that the JRZ RS line provides an excellent foundation for every configured kit.

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Understanding the Basics

Before delving into the nuances of the JRZ RS dampers, let's revisit some fundamental suspension principles. Having a sound understanding of the various components that constitute a coilover is crucial for making an informed purchasing decision. This is well summarized by motorsport expert Jay O'Connell in the SAFEisFAST series, and we have compiled the essential notes below.

• Springs act as the load-bearing elements that keep the vehicle elevated above the ground.
• Spring rate determines their stiffness, measuring the force required to compress them a certain distance.
• Numerous factors influence the choice of appropriate spring rates, with the main consideration being the need for stiffness adequate to support the car against aerodynamic loads.
• Ideally, the softest springs feasible should be used; softer springs typically yield greater tire grip. 
• Higher spring rates come into play when higher speeds result in increased aerodynamic forces (track conditions and specific car aerodynamics).
• Softer spring rates apply in scenarios with lower speeds and lesser aerodynamic forces.

• Dampers are tasked with managing the energy release stored in springs due to vehicle weight. They play a critical role in controlling vehicle mass and movement to maximize tire grip.
• When traversing uneven surfaces, compressed springs release their energy rapidly. The dampers' job is to moderate that release, maintaining vehicle stability and minimizing impact.
• Neglecting motion control due to deteriorated shock absorbers can detrimentally affect grip and overall stability.

• Rebound - Regulates energy release from springs when the wheel and tire move away from the body (shock expanding).
• Compression/Bump - Manages wheel and tire movement into the body/suspension (shock contracting).

• Bump stops protect dampers from bottoming out during suspension travel. They allow for lower ride heights without stiffening springs because they catch the car before it hits the limits of travel.
• However, it's important not to ride on bump stops, as this indicates the vehicle is low on travel.

• Anti-roll bars aim to mitigate chassis roll, maintaining tire camber angles relative to the ground to enhance grip throughout the lap.
• Stiffening the front bar can induce more understeer, while stiffening the rear bar typically leads to more oversteer.
• In understeering conditions, softening the front anti-roll bar can help regain grip at the front tires. Conversely, stiffening the rear bar may lessen grip at the back, complicating the handling of the already stable end.
• There are multiple approaches to addressing understeer/oversteer situations, starting with anti-roll bars. Adjustments may also involve spring rates, damper settings, and vehicle rake, leading to potential complexity in tuning.

Progressing Appropriately - JRZ RS Dampers

Often, aftermarket suspensions aimed at car enthusiasts do not genuinely enhance your vehicle’s handling capabilities. There’s no shortage of lower-grade dampers or coilover packages marketed attractively, so it’s crucial to comprehend what you’re purchasing. One common request from customers wanting new suspension components is the ability to adjust ride height. This feature is essential for various reasons beyond merely eliminating unsightly wheel gaps, as it serves as a fundamental aspect of any coilover design, warranting a higher standard of quality.

Premium coilovers are engineered around quality dampers tailored to a specific spring rate operating range. The calibration of these two components is essential to guarantee exceptional control over the vehicle’s dynamics on various road and track surfaces. The ultimate goal is to mitigate unwanted behavior transmitted to the chassis, preserving tire traction to maximize grip while offering consistent predictability for the driver. This should not be misconstrued with excessively stiff suspension, a common myth among car enthusiasts. It’s crucial to remember that not all coilover packages deliver equal performance.

The JRZ RS-Line is artisan-crafted on the same production line as the elite motorsport-grade dampers priced at $8,000 and beyond. The build quality and meticulous craftsmanship are unparalleled, evident the moment you unbox and inspect the components. Each piece undergoes anodization treatment, ensuring no exposed surfaces susceptible to corrosion. Given the hand-made nature of these dampers, every set is personally reviewed by a skilled technician, ensuring consistent quality before shipping to you.

Performance & Comfort A unique compression blow-off system filters out larger, high-velocity impacts encountered on rough roads or while navigating race track berms, situations that would typically challenge lower-end coilovers.

Longevity The upgraded shaft bearing enhances longevity between service intervals while simplifying rebuild processes. When service is due, JRZ collaborates with two partner service centers in the U.S. to perform all necessary work.

CNC Machining The internals of the JRZ RS Line dampers utilize CNC machining for precise damping characteristics. RS dampers are produced on the same lines as those for the Motorsport line.

Strut Coating Constructed from high tensile steel to endure extreme side loads, the McPherson struts from JRZ receive a premium black coating resistant to corrosion, sourced from an advanced supplier.

Experience the Difference Damper adjustments with JRZ are intuitive compared to other brands. Each adjustment "click" is discernible, not just through tactile feedback as you adjust rebound and compression settings, but also for the driver, enhancing the driving experience. For those who share our passion for suspensions, dialing in your JRZ setup becomes an enjoyable exploration.

The Key Question - How Much Do You Want to Fine-Tune Your Suspension?

In discussions with a diverse range of customers, this question often emerges as a pivotal consideration. Most agree on the desire for aftermarket dampers to perceptibly enhance handling characteristics, but the extent to which one is willing and able to fine-tune their dampers to optimize results is subjective. Since dampers constitute the central component of any high-performance suspension system, it's vital to weigh everything before deciding. What long-term goals do you have for your vehicle? Are you planning to compete in events with regulatory constraints? These factors should shape your purchasing decisions for lasting satisfaction.

I want to emphasize that all JRZ RS dampers are proficient in enhancing vehicle dynamics. When paired with appropriate supporting suspension elements and precise chassis alignment, they can considerably enhance the driver’s vehicle control capabilities. The question is how deeply you want to engage with tuning. As we explore the different available RS dampers, each model increases your capacity for fine-tuning suspension in a more detailed manner. Features that allow external modification of damping traits are particularly desirable for those pursuing improved lap times or competitive standing. Enthusiasts and racers often undertake the task of adjusting rebound, compression, and even nitrogen pressure to accommodate tire wear, track surface changes resulting in inconsistent grip, and even driver misjudgments.

RS ONE - Single Adjustable Dampers

The RS ONE is a single adjustable damper offering 21 precise clicks of adjustment, capable of handling a variety of spring rates. By simply turning one knob, users can adjust both rebound and compression, seamlessly transitioning between comfortable street setups, aggressive track configurations, or anything in between. The RS ONE design emphasizes simplicity without sacrificing standout performance. If you're not one to frequently alter spring rates, alignment settings, or other chassis setups, and prefer a reliable suspension that requires minimal intervention, the RS ONE dampers are an ideal choice.

With competitive pricing and prompt delivery, teao genuinely aspires to be your supplier and partner.

RS TWO - Double Adjustable Dampers

The RS TWO is a double adjustable damper, non-remote version that offers independent adjustments for both compression and rebound. This capability fosters more precise tuning, allowing users to achieve the desired suspension balance. The RS TWO offers 21 precise clicks of rebound adjustment via a knob on the strut’s upper portion, along with 14 clicks of compression adjustment from the knob located at the bottom of the strut.

For those looking to engage more deeply in the suspension tuning process or seeking the flexibility for more detailed adjustments as they advance their driving skills, the RS TWO offers straightforward capabilities without the complexity of external reservoirs.

RS PRO - Double Adjustable Dampers

With championship-caliber external reservoirs for optimal control, the RS PRO is a double adjustable damper. Like the RS TWO, it allows independent tuning of compression and rebound, making it suitable for both comfortable street setups and competitive racing. The RS PRO features 21 rebound clicks on the strut’s top knob and 14 compression clicks on the external reservoir.

The RS PRO serves as an effective choice for the suspension connoisseur, track enthusiast, or serious competitor. These dampers, complete with external reservoirs, cater to those eager to explore various spring rates, alignments, and setup features, all aimed at pushing their vehicles and their capabilities to the limit.

RS PRO 3 - Triple Adjustable Dampers

The RS PRO 3 represents the pinnacle of JRZ's offerings, featuring triple adjustability with championship-winning external reservoirs for superior control. It provides 21 precise clicks of rebound adjustment via a top knob, plus 14 high-speed compression and 8 low-speed compression adjustments through knobs located on the external reservoir.

Independently tuning high and low-speed compression allows both competitive racers and track enthusiasts to extract the utmost from their suspension systems. Double adjustable setups don’t permit users to isolate high and low-speed compression damping distinctly. Low-speed compression governs suspension responses over minor bumps, while high-speed compression manages rapid, abrupt surface transitions, such as navigating berths or sudden surface changes.

While additional adjustments may introduce complexity, it is essential to recognize that setting low-speed compression to maximum stiffness will cause the damper to function similarly to the RS PRO double adjustable variety. This gives users flexibility as they refine their cars over time, enabling fine-tuning to achieve an ideal setup tailored to specific track conditions. The RS PRO 3 is the go-to choice for passionate track enthusiasts and competitive racers seeking any potential edge over rivals.

Remote Reservoirs - Applicable to RS PRO & RS PRO 3

External reservoirs greatly enhance performance capabilities, facilitating a larger fluid volume and improved cooling efficiency. For track enthusiasts and competitors, external reservoirs are critical for maintaining consistent damping performance, ensuring reliability from the starting line to the checkered flag. Nitrogen pressure adjustments in the external reservoir, ranging from 150 to 350 PSI, are vital for racers seeking customized suspension setups.

The connecting lines to these reservoirs are sufficiently long for easy installation under hoods or in trunks, positioning them in cooler, accessible locations. All PRO packages come with front quick-disconnect lines for straightforward setup.

Some enthusiasts within the BMW community possess extensive experience and knowledge, enabling them to make informed decisions with relative ease. For others, information can be overwhelming; thus, we recommend one-on-one consultations with APEX Product Specialists to discuss individual goals, expectations, and budget effectively. We may not possess all the answers, but through collaboration with JRZ, Ground Control, and Hyperco, our staff delivers exceptional customer service both before and after your purchase. Remember, configuring and installing a suspension package is only half the journey. To maximize the benefits of your new purchase, it's crucial to know that expert support is available throughout the process.

Next, we'll delve into our Ground Control adjustable camber plates, rear shock mounts, baseline alignment suggestions for the E46 on both street and track, and take a closer look at our Hyperco linear race springs, helper springs, and guides. Stay tuned!

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