Corvette C4 1984-1996, Adjustable Suspension System - Lowering 10" Bolt Drop Kit w/BLACK Poly Bushings (12pc Set)

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Botello Dynamic Engineering (BDE) Systems LLC - Chevrolet Corvette C4, Suspension Lowering 10" Bolt Kit for 1984-1996 Corvettes (BLACK BUSHINGS), Complete 12-piece Rear Kit.

What's included with this sale:

  • QTY (2) Grade 8 Bolts, DIN 931 Metric in a 10" length in Yellow Zinc Chromate Plating - Our custom manufactured length for this C4 Corvette application – Made in the USA.
  • QTY (4) Grade 8 1.73” OD Oversized Washers, in Yellow Zinc Chromate Finish – Correctly oversized washers – Made in the USA.
  • QTY (2) Grade 8 Steel Nyloc (Locking) Nuts with Flared Base, in Yellow Zinc Chromate Finish – Made in the USA.
  • QTY (4) Energy Suspension Rear Bushings (1 complete rear set) made of Energy's HYPERFLEX Performance Polyurethane – Made in the USA – Style/Color: LOW-PROFILE, BLACK BUSHINGS
  • QTY (1) Install Instructions – Basic pamphlet guide including color images.
  • QTY (1) Packing Slip
  • QTY (1) USPS Priority Mail Shipping (2-3 Day Service) with tracking & insurance - USA customers only
***International Customers Pay $19.99USD for Export/Import, VAT Fees, International Customs Paperwork, Tracking and Delivery***


We understand that you may not be completely satisfied with the current wheel gap in your C4 Corvette. As fellow owners of two C4s, we can relate to the frustration of seeing our beloved cars sit higher than desired, especially after installing a set of attractive wheels. While some individuals attempt to address this issue by using OEM hardware to adjust the suspension, the results often fall short in terms of achieving the desired drop, material finish, and ride quality. At BDE-Systems, we specialize in developing lowering kits specifically tailored for Corvettes, and we are pleased to present our refined version of the 11" bolt kit. Short of opting for a custom coil-over/track setup, our C4 Lowering Kits offer a swift and cost-effective solution to enhance both the aesthetics and ride of your Corvette. These kits have been available for purchase on our website,, as well as on renowned platforms such as The CorvetteForum and eBay since 2014. We are proud to announce that as of 2023, our kits are also accessible through LLC.

It is important to highlight that the lowering/ride height provided by our kit is fully adjustable to your preference and wheel/tire setup. The development of this C4 kit was guided by our own 1987 and 1994 Corvette C4s, as well as invaluable feedback from select members of The CorvetteForum and their respective vehicles. This collaborative effort allowed us to consider a wide range of suspension requirements and formulate the comprehensive kit we present to you today.

Thank you for considering our C4 Lowering Kit. We are confident that it will not only transform the appearance of your Corvette but also significantly improve its ride quality.
THIS LOWERING/RIDE HEIGHT PROVIDED BY THIS KIT IS ADJUSTABLE TO YOUR LIKING - This C4 kit was developed using our own 1987 and 1994 Corvette C4s along with feedback from a few members of The CorvetteForum and their vehicles; thank to this, we used the valuable input for a variety of suspension needs and formulated the kit presented here today. Furthermore, we rigorously test and utilize all our kits and products on our very own BDE-Systems Corvettes that we are fortunate to own:

  1. 1987 Corvette TPI - Modded
  2. 1994 Corvette LT1 - Modded
  3. 2003 Corvette Z06 - Modded
  4. C6 Z06 we presently have at 714 crank HP on E85, our 2020 addition to the stable.

Rest assured; we aren't a reseller or parts flipper looking for a cheap & quick dollar - We daily drive what we sell, CORVETTE.



Strength Matters

BDE-Systems Lowering Bolts have been meticulously engineered to adhere to the highest standards of quality and strength. Our bolts are classified as Grade 8/Metric Class 10.9, complying with the esteemed DIN 931 certification. Furthermore, it is essential to highlight that the entire hardware kit provided by BDE-Systems LLC also meets or surpasses the rigorous Grade 8 standards as outlined by ASTM A324 Grade BD and SAE J429. This guarantees the utmost level of quality, durability, and strength in the components.

It is important to emphasize the significance of these designations, as it is not uncommon to find kits in the market that utilize Grade 5 hardware instead. Such a substitution of the original Grade 8 design not only bypasses the scrutiny of GM's Engineering Team but also poses a risk to both your vehicle and personal safety. These shortcuts are typically motivated by cost-saving measures, compromising the integrity and performance of the kit.

Grade 5 hardware is characterized by its lower quality and is primarily intended for general applications, such as carpentry, household use, and low-stress domestic purposes. The absence of appropriate certificates of conformance or lot traceability for lower tensile strength hardware further emphasizes the disparity in quality. Conversely, Grade 8 hardware, like that employed by BDE-Systems, undergoes stringent testing, and conforms to specific standards, ensuring its suitability for demanding automotive applications. Grade 8 hardware stands as a superior choice compared to Grade 5 due to several significant factors that contribute to its enhanced strength and reliability. In the realm of fasteners and mechanical components, the grading system provides a standardized means of categorizing the tensile strength and overall quality of materials used. Here are the key reasons why Grade 8 hardware surpasses Grade 5:

  • Tensile Strength: Grade 8 hardware exhibits a higher tensile strength compared to Grade 5. Tensile strength refers to the maximum load a fastener can bear before breaking. Grade 8 fasteners are engineered to withstand greater forces and loads, making them ideal for applications that demand high load-bearing capacities and structural integrity.
  • Carbon Content: The disparity in tensile strength can be attributed to the higher carbon content in Grade 8 hardware. Carbon is a crucial element that enhances the strength and hardness of the material, enabling Grade 8 fasteners to withstand greater stress and deformation without compromising their integrity.
  • Alloying Elements: In addition to carbon, Grade 8 hardware incorporates alloying elements such as chromium, molybdenum, and vanadium, among others. These elements further enhance the strength, hardness, and overall performance of the fasteners, providing them with superior resistance against deformation, shearing, and fatigue.
  • Durability: The increased strength and robustness of Grade 8 hardware translates into improved durability. Grade 8 fasteners are designed to withstand harsh conditions, heavy vibrations, and extreme temperatures without compromising their structural integrity. This durability ensures long-term reliability and minimizes the risk of failure or damage.
  • Safety and Reliability: The use of Grade 8 hardware ensures a higher level of safety and reliability in critical applications. By utilizing fasteners with superior strength and load-bearing capabilities, the risk of fastener failure, structural collapse, or mechanical breakdown is significantly reduced, enhancing overall operational safety and stability.
  • Industry Standards: Grade 8 hardware adheres to strict industry standards and specifications, such as those outlined by organizations like the American Society for Testing and Materials (ASTM) and the Society of Automotive Engineers (SAE). These standards ensure consistent quality and performance, as well as compatibility with various industry applications and requirements.

In summary, Grade 8 hardware surpasses Grade 5 in terms of tensile strength, carbon content, alloying elements, durability, safety, and compliance with industry standards. The superior properties of Grade 8 fasteners make them the preferred choice for applications that demand robustness, reliability, and optimal performance under demanding conditions. By selecting Grade 8 hardware, engineers, manufacturers, and individuals can ensure the longevity, safety, and efficiency of their projects or equipment.

  • Common Aftermarket Bolt Rating: Grade 5 or worse - It is important to note that a common rating for aftermarket bolts is often Grade 5 or even lower. When purchasing from a vendor who does not explicitly specify the Grade/Class Bolt, there is a high probability that substandard materials are being used. These inferior materials are typically obtained at lower costs locally or through online channels, and then resold to unsuspecting customers.
  • BDE-Systems Bolt Rating: Grade 8/Class 10 - Our bolt grade matches the OEM GM factory bolt Grade 8 rating.

Grade 8 bolts exhibit superior tensile and shear strength compared to Grade 5 bolts, with certified levels of over 21% higher in shear strength and 25% higher in fatigue/tensile failure levels. This advantage extends to metric bolts as well, specifically when comparing Class 8.8 to Class 10.9. The lower grade bolt, in both cases, reaches its maximum elongation and fracture point significantly earlier than the higher-grade bolt, which demonstrates its superior resistance to deformation.

Since the 1950s, General Motors (GM) has been utilizing Class 10/Grade 8 bolts in the rear suspension of their automobiles and Corvettes. The selection of Class 10/Grade 8 bolts by GM reflects their confidence in the strength and reliability of these bolts for critical automotive applications. It is worth noting that all BDE-SYSTEMS LLC kits we offer maintain the same class/grade as the original equipment manufacturer (OEM) used by GM plants. By aligning with GM's choice of Class 10/Grade 8 bolts, BDE-SYSTEMS LLC ensures that their kits maintain the highest standards of quality and performance. This commitment to utilizing the same class/grade as the OEM highlights their dedication to delivering products that meet or exceed the specifications and requirements set by reputable automotive manufacturers. 

Here is just a small sample size of CorvetteForum users that you can look up as they have had their lower GRADE 5 BOLTS FAIL - You don't need to purchase from us but please ENSURE you are getting GRADE 8 materials only: 

  • CorvetteForum Senior Member Greengear - failed lower grade bolts
  • CorvetteForum Senior Member Kinkajou - failed lower grade bolts
  • CorvetteForum Senior Member FR 73 454 - failed lower grade bolts
  • CorvetteForum Senior Member Danbo - failed lower grade bolts
  • CorvetteForum Senior Member C5Natie , he and I had our friend in LA total his C4 over a weaker rear bolt failing at highway speeds, fortunately accident was not fatal - failed lower grade bolts




 Quality and Certification Matters

BDE-Systems LLC is an approved Amazon FBA Business Partner (2023). We maintain on-site Certificates of Conformance and Lot Traceability records for the materials utilized in our products. While we have done this for many years, our recent certification meant that our records underwent a thorough evaluation by LLC during the application process for our current Amazon FBA Business Account, resulting in successful approval. By diligently preserving Certificates of Conformance (CoC) and Lot Traceability records, we uphold a high standard of accountability and quality assurance. These records serve as tangible evidence of our commitment to meeting and exceeding industry requirements and regulations, and our commitment to you. The evaluation and approval of our records by LLC for our Amazon FBA Business Account further validates our adherence to stringent quality control measures. This endorsement from a reputable platform highlights our dedication to upholding the highest standards in our business operations.

When evaluating kits or components, it is crucial to prioritize transparency regarding the material, grade, and class of the hardware being utilized. Kits that fail to mention or provide details about the hardware used are highly likely to incorporate Grade 5 alternatives. By being vigilant and selecting kits that adhere to Grade 8 standards, you can safeguard the performance, reliability, and safety of your vehicle.

Our hardware finish exceeds OEM GM standards as our bolts, nuts and washers are treated to a yellow zinc chromate coating to protect your new kit from the natural elements for many years to come. Yellow zinc chromate is a chemical conversion coating that is applied over zinc plating during the surface coating process. Zinc plating is a soft, ductile, marginally solderable, corrosion-resistant finish. It protects the substrate and corrodes before the base metal, unlike most other commonly plated metals, thus protecting your new Grade 8 Steel parts.

With the combination of the rear Grade 8/Class 10.9 bolts, Grade 8 non-marring flanged nyloc nuts, Grade 8 oversized washers (hardware in a matching yellow zinc chromate, providing years of protection from the elements) and Hyperflex Polyurethane low profile bushings, this is the best quality and performance C4 bolt lowering kit that any Corvette manufacturer or vendor carries.




Adjustability Matters

BDE-Systems C4 10" Lowering Bolts provide an increase of 1.00" in overall length when compared to the OEM bolts, this allows for an extended threaded rod portion to be used for compressing/decompressing of the C4 suspension, which provides an increased range of ride height adjustment (well past simply dropping your C4 using the OEM bolts). We found that the 9.5" bolt length would leave some adjustment room on the table and often left the nut at the end of the bolt threads. We tried a 12" bolt and while it worked, it’s not a length we recommend on certain models as select aftermarket wheels may change the wheel offset/height/width and in turn, alter the general suspension geometry and spacing in relation to the bolts/suspension components vs the wheel/tire, possibly causing interference or a tire puncture. We found the 10" bolt to be an excellent compromise in both areas, lowering/adjustable range and maintained a safe distance from potential interference with the rim and tire, even with aftermarket wheels. IF YOU NEED ADDITIONAL DROPPING PAST THIS KIT, WE DO OFFER AN 11" BOLT KIT, WHICH IS OUR ORIGINAL, LONGEST AND BEST-SELLING KIT. PLEASE SEE OUR OTHER AD FOR OUR 11" BOLT KIT.




 Trusted Partnerships Matter - Completing the Package:


To round off our Complete Rear Lowering Kit, we've partnered with Energy Suspension Bushings for our bushing needs. Energy Suspension is a well-established company in the suspension market for OEM or aftermarket components with an impeccable reputation in the field. 

Have you ever heard the rear of your Corvette squeak and squeal? Or perhaps notice a slight height difference between each side? It could be that your original crushed rubber pads have gone out on you. When replacing the rear bolts, out along will come the OEM GM rubber pads that will most likely be beat down and cracked so why not take this moment to replace them with Energy Suspension’s Hyperflex Performance Polyurethane? Longer lasting performance polyurethane pads are smart to install whenever the spring assembly is reassembled. Benefits of our low-profile poly pads:

  1. Adds a dramatic amount of performance and durability to any vehicle
  2. Helps the vehicle be in control when maneuvering through turns, during standing start accelerations, braking, even over bumps and berms.
  3. Made of Energy's HYPERFLEX performance polyurethane.
  4. Improved traction and handling




The Advantages of Lowered/Adjustable Suspension

In general, having the vehicle lower to the ground can increase the grip of the tires on the roadway by reducing the suspension travel to have body weight and momentum shifted to the rear wheels. Additional stiffness can be desired in a suspension, and this is one of the perks that some drivers mention after lowering their suspension.

Body roll reduced
When the center of gravity has lowered one generally reduces body roll which in turn increases the responsiveness of the car. C4 Corvettes aren't known rollover adverse vehicles but if there was a threshold or propensity of it, it would be reduced by lowering it.
Stock wheels and body spacing
This may not be news to you Corvette owners out there, but the suspension and ride height varies from Corvette to Corvette. Reports vary on stock height, but we've seen heights from about 26" to about 30", and we attribute this to suspension condition, year & model variances in suspension options and miles on suspension. This kit is an excellent way to remedy those variances and stabilize the rear end.
Aftermarket wheels and body spacing
When moving into the aftermarket wheel world it is often a necessity to lower the ride height of one’s vehicle to close the wheel gap and achieve that perfect stance. Our 1994 Corvette has 19" aftermarket wheels while our 1987 Corvette has 17" aftermarket wheels (OEM wheels were 16") so the kits allowed us to match the wheels to the ride height very easily – This will apply to your Corvette, the adjustability will work with your wheel and tire setup.
Better aerodynamics
With a lowered suspension, there's less air going underneath the vehicle, and this can create a better outcome for wind drag on a car. GM did design the vehicle with a rake for stability at high speed so keep at rake if that's your intended range - adjusting and monitoring the height at speed in conjunction with adjustments is recommended. The speeds we are talking about are off-road speeds not seen on commercial/commuter/highway roads. In other words, adjusting your height is fine for regular street and highway use without need to worry but if you drive in the 130+MPH range for sustained periods of time then monitoring/adjustments are recommended, just like any other lowering.


  1. Buy from anyone you'd like but for your own safety, find a reputable manufacturer, reseller or source as a few dollars difference CAN buy peace of mind.
  2. DONT REPLACE YOUR OEM Bolts WITH GRADE 5, CLASS 8, unmarked, OR local hardware surplus parts.
General and/or Limited Liability clauses WILL NOT protect a corporation, company, or individual selling lower grade hardware in place of the OEM Grade 8 hardware.
Please bear in mind that ultimate shear strength of a fastener is typically about 60% of its ultimate tension strength. In addition, cyclic fatigue and continual loading cycles will EVENTUALLY stress the subpar steel leading to a failure (usually at speed, under road strain).
GM and nearly all vehicle manufacturers use GRADE 8 Bolts in high stress suspension components such as the rear of your Corvette.
BDE-Systems LLC will only sell you the correct, OEM strength Metric Class 10.9/Grade 8 Hardware Required by General Motors Corp. Certs of Conformance and Lot Traceability records kept on site and are available for review.




FREE USPS Priority Shipping & Tracking is included to The United States with the sale price unless otherwise noted.

***WORLDWIDE SHIPPING! *** We can ship to virtually any address in the world and are glad to serve our Corvette Customers overseas. The free shipping applies only to Continental US customers, but we do have a global business shipping account and all other locations only pay a flat rate of $19.99 as the International Shipping Rate. This includes customs paperwork, export/import and VAT fees.

Items will be shipped within 1 business day after receiving a clear payment, same day shipping is carried out when/where possible.


 Returns Policy

We accept returns although we rarely see them; however, if there is ever an issue or concern, we are always willing to work it out if you contact us immediately. We will always strive to reach an amicable agreement upon any reports of concerns. You may also return an item if we shipped the incorrect item to you (wrong color or incorrect item) - at which point we will refund the new, unused item cost within 14 days of delivery for a full refund. We'll also pay the return shipping costs if the return is a result of our error (you received the wrong color or incorrect item, etc.). You should expect to receive your refund within three weeks of giving your package to the return shipper, however, in many cases you will receive a refund within a faster time frame, that is a worst case/special circumstance scenario. This period includes the transit time for us to receive your return from the shipper (3 to 7 business days), the time it takes us to process your return once we receive it (2 to 4 business days), and the time it takes the bank system to process our refund request (1 to 2 business days). We strive to ensure your satisfaction and our customer support line is there to walk you through the installation, answer technical questions and offer advice on installation methods. If you need to return an item, please Contact Us with your order number and details about the product you would like to return. We will respond quickly with instructions for how to return items from your order.


Thank you for taking the time to visit us here at Botello Dynamic Engineering (BDE) Systems LLC. We were founded in 2014 with the intention of bringing the Corvette market a breath of fresh air with new products. We’re an LLC based out of Ventura County California and all our materials for our products are sourced in the United States. BDE-Systems is a minority owned, disabled US NAVY Veteran with all our eBay sales generating a percentage of charitable contributions to The NAVY SEALS FUND at Thanks to the response in the C4 Corvette market over the last few years, we have been able to expand into the C2, C3, C5, C6 and C7 market Corvette market - Due to all the continued and consistent sales/community support, we purchased a C5 Z06 and a C6 Z06 Corvette. These vehicles are not just enjoyed by us daily, they have served as "test mules" and allowed us to release/research additional products or services in this field; thankfully, we also gained new partnerships in the Corvette and Automotive Industry in doing so.


Thank you,

Eli Botello

Owner of BDE-Systems LLC