To start things off, we will be taking a look at our most popular and versatile suspension setup, the BC Racing BR Series. Most people assume that since the BR Series is our entry-level street setup, it lacks the quality and performance of our higher valued units such as the RM and ER Series. Fortunately, that is not true. The RM and ER Series (which will be covered in following segments) are simply molded for more specific uses, such as circuit and drag racing. The same quality, adjustability and durability remains throughout all variants of the BC Racing Coilover line.
The BC Racing BR Series Coilovers are perfect for a wide range of customer needs. They are well suited for daily driving, autocross, circuit racing and stance vehicles. The biggest strength of the BR Series Coilover system is the ability to customize it using varied shock and spring lengths with matched valving to suit your individual needs. Many of you are familiar with one of our variations named the “extreme drop” which will be covered in depth in a later spotlight.
A governing design element for BC Racing is to design our kits to be as similar to an OEM replacement as possible. We take care to design our suspension in a manner that not only bolts up easily in the factory location, but is also easy to adjust. Achieving this means utilizing any and all OEM mounting brackets and supports for brake lines, wheel speed sensors, etc. What does this mean to you as the customer? For example, if you own a Nissan 350Z, which is one of our more popular platforms, our kits are designed and fitted to sit in the OEM locations. The front bolts up perfectly with all necessary OEM brackets and the rear is the OEM designed independent rear setup (separate spring and shock). The OEM suspension geometry will then be kept as close to OEM as possible while allowing the adjustability our customers have come to demand. All BC Racing Coilover kits start with obtaining the factory OEM suspension and measurements of the vehicle. We then reverse engineer the suspension to produce a prototype kit. The OEM shocks and springs are shock dyno tested in order to determine the valving and spring rates of our default coilover configurations. Each setup is then tested on the vehicle in our own facility for a period of 6 months before it is officially released to the public for purchase.
BC Racing top plates are constructed from a solid piece of 6061-T6 aluminum ensuring a lightweight and incredibly strong design that is finished in our signature BC Racing Gold. Take a quick look at the picture above and you will see 3 main top plate designs. From left to right we have a camber/caster plate, camber plate, and rubber top plate. Currently, the camber/caster plate is available for a very limited number of vehicles equipped with MacPherson type suspension. If you require that type of adjustability, it is always best to check with us on availability for your specific application.
The BC Racing camber plate is standard on all kits that can utilize them (MacPherson style OEM suspension). The BC Racing camber plate will allow a maximum of 3 degrees of camber adjustment on its own like the camber/caster plate. Please note that this does not take into account the amount of natural camber you gain from simply lowering the vehicle. One thing to note about the camber plate as well as the camber/caster plate is that it will offer a trade off in terms of noise, vibration, and harshness (NVH). You gain camber adjustability but sacrifice NVH due to increased road noise being transmitted up through the metal bushings and into the cabin. For a track dedicated car this is generally preferred.
BC Racing rubber top plates are utilized frequently on our kits. If the front of the vehicle utilizes a camber plate, the rear will use a rubber top plate, although pillowball tops are frequently available for dedicated track vehicles. For all kits in which a camber plate cannot be utilized (A-arm suspensions) the top plates will be rubber front and rear. The main design feature of the rubber top plate is that it dampens NVH from reaching the cabin as much as possible enabling an OEM-like quiet ride. All rubber top plates have a durometer rating of 70A in order to achieve the best balance between performance and comfort.
The pillowball top plate shown above is used as an upgrade in the rear of a vehicle in lieu of the rubber top plate. Rubber is used as standard to limit NVH from making its way into the cabin although this upgrade is available on various chassis at the customer’s request. Please contact us directly to see what options are available for your specific platform. The pillowball top plate is a good upgrade for customers seeking a more track oriented, rigid setup where NVH is not much of a factor. A feature on our top plate combinations will be coming soon.
The BC Racing pillowball casings feature chromium plating for rust protection to improve longevity and efficiency of the casing. The Allen bolts we select for use on our camber plates are stainless steel for durability and longevity through the harshest of environments. Our top nut design secures the shocks piston shaft to the top plate and are made of carbon steel with a yellow zinc plating. The top nut has a built in bushing to help the nut bite down and lock onto the pillowball casing for added strength and safety.
BC Racing utilizes the highest quality Koyo bearings available between the top plate and the top of the spring. It is a sealed and self lubricating bearing that is pressed into our upper spring seat during the assembly process. The 6061-T6 aluminum is milled down in the center and the Koyo is pressed in. A yellow zinc plated misalignment spacer is then used to mate the top of the Koyo bearing to our pillowball casing. The entire assembly allows rotational movement to decreases friction when the steering wheel turns. Without this bearing it is possible for the spring to bind during turning which creates a “twang” type spring sound.
BC Racing utilizes 3 main spring designs as pictured. We have from left to right: linear, S-barrel, and V-barrel. All of these springs have their intended uses in our coilover systems depending on the OEM suspension design as well as the design of our kits Every one of our springs is made of SAE9254 steel material and utilizes a Zinc coating under the outer powder coating to ensure rust does not penetrate the metal of the spring and compromise performance/reliability.
The linear springs we offer cover a wide variety of suspension setups available. The liner spring is an industry standard 62mm I.D. (inner diameter) available in many different lengths and rates to suit our customer’s needs. We have springs available in as small as 120mm length and as great as 260mm length.
There are instances when we are not able to utilize a linear spring. Such is the case on many independent rear suspension vehicles. For these instances we use an S-Barrel type spring. This S-barrel spring uses the same 62mm I.D. measurement on both ends but in the center the winds are bowed out to allow for greater spring stroke with the use of a shorter spring. The S-barrel is perfect for the rear of most independent rear vehicles simply because when the spring compresses over rough terrain, the winds will not touch and create noise.
On many newer vehicle applications, none of the previous options are useable for the rear of an independent suspension chassis. Many manufacturers now use different sized mounting points for OEM springs. In these instances, we create a custom wound spring classified as a V-barrel. Utilizing a V-barrel allows our spring to fit in the OEM spring cup while allowing us to size the other end for our height adjusters. Full height adjustability is retained to our specifications but there is a draw back; since the spring is custom wound for the application, your choices in shorter and stiffer/softer springs are limited, and sometimes to a single option. Through constant development of our kits, if we see demand for a higher or softer rate, we will produce it and begin to offer it to our customer base.
A common question associated with our springs relates to understanding how to properly read the part number in order to determine the rate, length and size. Consider the above spring for instance and the break down. The picture above shows an S-barrel type spring with the part number clearly printed in white. The rubric to deciphering the labels is:
62- Refers to the I.D. of the spring on both sides
180- Refers to the static length of the spring in mm
08- refers to the spring rate in Kgf/mm
On a V-barrel spring you will notice 4 sets of numbers instead of the 3. The rubric to decipher this is:
62- Refers to the ID of the smaller end of the spring
97- Refers to the ID of the spring where it mates to the OEM spring bucket
210- Refers to the static length of the spring in mm
08- Refers to the spring rate in Kgf/mm
Using this information correctly while taking into consideration shock length will allow you to properly customize our kit to suit your individual needs.
The lock rings we use are made of the same 6061-T6 aluminum found in our top plates. The lock rings utilize a thread pitch of M53x2.0 on our most common BR Series shock to thread onto our shock bodies. Each lock ring is sandblasted at our factory and then coated with a yellow anodize to help protect it from harsh environments.
The picture above is of our spring seat. The spring seat is where the bottom of the spring sits. Between the spring and lock ring there will be a hard plastic spacer known as a spring seat isolator. This ensures that there is no metal-to-metal contact for the quietest operation possible. This spring seat is also responsible for spring preload.
Our basic lock ring is located under the spring seat. This ring is special because its primary function is to torque against the spring seat and lock it in place. The lock ring will torque and secure itself to the spring seat securely once properly tightened so that the preload does not change unless the customer decides to make a change. The spring seat and basic lock ring are the two rings that are responsible for gaining leverage to make height adjustment for our coilover systems. Please note that you do not turn the rings independently to adjust height, you simply use them as a leverage point to rotate the shock body into and out of the lower mount to adjust height, but they must be locked together to achieve this.
Take a look at our lower lock ring and you will notice it is much different than the others. The lower part of the lock ring is conical in shape to allow the lock ring to bite into and secure the shock body, which prevents it from moving in any direction. It is possible to over tighten this lock ring resulting in an inability to adjust ride height. It is recommended to only hand-tighten this lock ring using our supplied spanner wrenches.
The lower lock ring is tasked with keeping the shock locked into place once final ride height is selected. The lower lock ring must be loosened before making any sort of height adjustment and locked down properly afterwards using our spanner wrenches.
If you want to lower the vehicle, you spin the spring seat clockwise to thread the shock body into the lower mount.
If you want to raise the vehicle, you spin the above pictured lock ring to thread the shock body out of the lower mount. Both the spring seat and lock ring have to be locked together to make this possible without changing spring preload.
In the picture above you will see our BC Racing shock bodies. We are now at the center point of our kit. As you can see, we have a wide variety of shock types, lengths and diameters. Pictured above is just a small sample of the varying shocks we offer for different applications. Each vehicle depending on our data from R&D, and accounting for the OEM suspension design will utilize a different style of shock. Each shock is hand assembled in our factory and dyno tested before use in our kits. Shocks are paired together by their compression and rebound numbers after dyno testing to a 5% variance from side to side. This means that in your kit, the fronts and rears are paired almost exactly the same to ensure proper ride quality and performance of the suspension. The shocks used in most of our systems utilize a 53mm shock body. In the event there are space concerns, we use smaller diameter shocks to ensure proper clearance and operation of the suspension under load. Each shock is coated in black chrome for a clean, cohesive appearance, and to help with corrosion resistance.
As many of you know, we provide an extreme drop option for some of our popular kits. Generally, an extreme drop version of our kit utilizes a 1-inch shorter shock paired with an appropriate length spring. This customization allows our customers an extra inch to inch and a half drop over the standard kit. If a customer has a request for an even lower drop, we are willing to work with those needs and attempt to tailor the kit to the customers requested specifications. The reason extreme drop kits are limited to a 1-inch lower drop is because of standard chassis clearance issues. Many cars, such as the VW platforms, cannot go past our regular kit’s drop without modifying the subframe. Not every customer is prepared to make such a modification on his or her vehicle to achieve a certain appearance. A one inch lower drop is generally the lowest we can safely provide without necessitating extra modifications to a vehicle’s chassis. We are in business to provide performance enhancing suspension but safety and ride quality are of primary concern.
Last but certainly not least is the lower mount. The lower mount is where our suspension bolts to your wheel hubs. Each lower mount is designed to be an OEM replacement. We provide any and all OEM mounting points and brackets that were on the OEM shock. The lower mount, and the upper mount, is where reverse engineering the OEM suspension plays its biggest role. The process ensures everything is welded and mounted in OEM positions so that your brake lines, wheel speed sensors, and harnesses are a direct fit. Our lower mounts, whenever possible, are made of STKM13C steel and all brackets are welded robotically. Once the lower mount is completed, it is then sand blasted and powder coated in order to prevent rust and corrosion.
In instances when the OEM suspension is designed as a fork or eye-bolt type, we engineer the lower mount of out the same 6061-T6 aluminum as our top plates. Each lower mount is milled from a single piece of aluminum based precisely on the measurements obtained through the reverse engineering process. Each lower mount is then checked against OEM measurements for quality control before receiving a black powder coat.
Article by- Sam Bracero