Botello Dynamic Engineering (BDE) Systems LLC

Chevrolet Corvette C4 Rear Suspension 11" Lowering Bolt Kit

1984–1996 Chevrolet Corvette (Red Bushings) - Complete 12-Piece Rear Suspension Lowering Kit

What's Included

• Qty. (2) Grade 8 / Metric Class 10.9 DIN 931 11" Lowering Bolts with Yellow Zinc Chromate Finish – Made in the USA
  The longest C4 Corvette Lowering Bolt Kit available.
• Qty. (4) Grade 8 Oversized Washers (1.73" O.D.) with Yellow Zinc Chromate Finish – Correctly sized for maximum load distribution – Made in the USA
• Qty. (2) Grade 8 Flanged Nyloc Lock Nuts with Yellow Zinc Chromate Finish – Made in the USA
• Qty. (4) Energy Suspension Hyperflex Performance Polyurethane Rear Bushings (One Complete Rear Set) – Low-Profile Red Bushings – Made in the USA
• Qty. (1) Installation Guide with color photographs
• Qty. (1) Packing Slip
• USPS Priority Mail (2–3 Business Days) with tracking and insurance for U.S. customers

International Shipping

International customers pay $34.99 USD for export processing, customs documentation, tracking, and delivery. Import duties, VAT, taxes, and any country-specific fees are the responsibility of the buyer.

BDE-Systems LLC understands that many C4 Corvette owners are looking to reduce the factory wheel gap, especially after installing a new set of wheels or suspension ages. We own a pair of C4 Corvettes and always understood the need for adjustments to adjust the high factory ride height, adjust to custom/modern wheels, overall improve stance and appearance. While some owners use the OEM hardware to adjust ride height, the available adjustment is often limited and may not achieve the desired stance or overall appearance.

At BDE-Systems, we've specialized in Corvette lowering kits since 2014 and are proud to offer our refined 11" C4 Lowering Kit. This is the longest bolt kit available on the market = lower stance/greatest adjustment range. Short of a custom coil-over or dedicated track suspension, it provides a fast, affordable, and fully adjustable solution to improve both the appearance and ride quality of your Corvette.

Our lowering kits have been available through BDE-Systems.com, CorvetteForum, and eBay since 2014, and have been offered through Amazon since 2023.

Ride height is fully adjustable to accommodate your personal preference, suspension condition, and wheel and tire combination. This kit was developed using our own 1987 and 1994 C4 Corvettes, along with valuable feedback from CorvetteForum members, allowing us to refine a kit that meets a wide range of suspension needs.

Every BDE-Systems product is designed, tested, and used on the Corvettes we own and drive:

• 1987 Corvette TPI – Modified
• 1994 Corvette LT1 – Modified
• 2003 Corvette Z06 – Modified
• C6 Z06 – 714 HP on E85

We aren't a reseller or parts flipper looking for a quick sale—we're Corvette enthusiasts who engineer, test, and daily drive the products we sell.

Size Matters

OEM GM Bolt Length: 9.00"

Typical Aftermarket Lowering Bolt Length: 10.00"

BDE-Systems Lowering Bolt Length: 11.00"

Our 11" lowering bolt provides the widest range of ride height adjustment, allowing approximately 0.1" to over 4" of rear suspension drop, depending on suspension options, vehicle weight, mileage, and overall suspension condition—similar to any adjustable coil-over or lowering system.

Ride height is easily adjusted by simply threading the Grade 8 nut along the extended bolt to achieve your desired stance.

Strength Matters

BDE-Systems Lowering Bolts are engineered to meet the highest standards of quality, strength, and durability. Our bolts are manufactured to Grade 8 / Metric Class 10.9 specifications and comply with DIN 931 standards. In addition, every component in our hardware kit meets or exceeds ASTM A324 Grade BD and SAE J429 Grade 8 requirements, ensuring OEM-level strength throughout the entire assembly.

Unfortunately, not all aftermarket lowering kits maintain these standards. Some manufacturers substitute lower-cost Grade 5 hardware in place of the OEM Grade 8 design to reduce production costs. While suitable for general-purpose applications, Grade 5 hardware was never intended for critical suspension components and may compromise both performance and safety.

Compared to Grade 5, certified Grade 8 hardware provides:

• Over 21% greater shear strength
• Approximately 25% greater tensile and fatigue strength
• Increased resistance to stretching and permanent deformation
• Improved durability under repeated suspension loads

The same advantages apply when comparing Metric Class 8.8 fasteners to Class 10.9. Lower-grade fasteners reach their elongation and failure point significantly sooner than higher-strength hardware.

Unlike lower-grade hardware commonly used in general construction, household, and light-duty applications, Grade 8 fasteners are specifically engineered, heat-treated, and tested for demanding automotive and industrial environments. Their higher carbon content and alloy composition provide greater strength, durability, and resistance to shear, fatigue, and repeated loading.

Why Grade 8 Matters

• Higher tensile and shear strength
• Greater resistance to fatigue and deformation
• Improved long-term durability
• Increased safety and reliability in high-stress applications
• Manufactured to strict ASTM and SAE industry standards

Typical Aftermarket Hardware: Grade 5 or lower*

Many aftermarket kits do not identify the grade or class of the supplied hardware. If the hardware grade is not clearly specified, there's a good chance lower-strength fasteners are being used.

BDE-Systems Hardware: OEM-Equivalent Grade 8 / Metric Class 10.9

Our hardware matches the strength classification used by General Motors for the factory rear suspension.

Since the 1950s, General Motors has relied on Grade 8/Class 10 hardware in high-stress rear suspension applications, including the Corvette. Every BDE-Systems lowering kit maintains the same OEM strength classification, providing the durability, reliability, and safety expected from a critical suspension component.

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 has been an approved Amazon FBA Business Partner since 2023. As part of the approval process, Amazon.com LLC evaluated our quality documentation, including our Certificates of Conformance (CoC) and Lot Traceability records, validating the quality control standards we've maintained for years.

We maintain complete on-site Certificates of Conformance and Lot Traceability records for the materials used in our products. These records provide accountability, material verification, and manufacturing traceability, demonstrating our commitment to consistent quality and customer confidence.

When comparing lowering kits, always verify the material, grade, and class of the supplied hardware. Manufacturers that do not clearly identify these specifications are often using lower-grade alternatives. Choosing a kit built with certified Grade 8 / Metric Class 10.9 hardware helps ensure the strength, reliability, and safety your Corvette's suspension demands.

Our bolts, nuts, and washers feature a durable yellow zinc chromate finish that exceeds the corrosion protection of the original OEM hardware. Applied over zinc plating, this conversion coating protects the steel by sacrificing the zinc before the base metal, helping resist corrosion and preserve the appearance of your Grade 8 hardware for years to come.

Combined with our Grade 8 / Metric Class 10.9 hardware, non-marring flanged nyloc nuts, oversized hardened washers, and Energy Suspension Hyperflex low-profile polyurethane bushings, BDE-Systems delivers one of the highest-quality and best-performing C4 Corvette lowering kits available.

Adjustability Matters

BDE-Systems C4 11" Lowering Bolts are 2.00" longer than the OEM GM bolts, providing the maximum range of ride height adjustment available. The extended threaded section allows for greater suspension compression and decompression than the factory hardware, giving you significantly more adjustment than the OEM bolts alone.

During development, we tested multiple bolt lengths to determine the optimal balance of adjustment range and safety. We found that 9.5" bolts limited the available adjustment and often left the nut near the end of the threads. While a 12" bolt provided additional adjustment, it also increased the possibility of interference with certain aftermarket wheel and tire combinations due to changes in offset, width, and suspension geometry.

Our 11" bolt proved to be the ideal solution, delivering the maximum practical adjustment range while maintaining safe clearance from the wheel, tire, and surrounding suspension components—even with most aftermarket wheel combinations.

If you're looking for a modest ride height adjustment over the OEM bolts, we also offer a 10" Lowering Bolt Kit. Please see our other listings for additional details.

 Trusted Partnerships Matter - Completing the Package:

Energy Suspension Hyperflex Performance Polyurethane Bushings (Low-Profile)

To complete our C4 Rear Lowering Kit, we've partnered with Energy Suspension, one of the most respected names in performance suspension components for both OEM and aftermarket applications.

If you've noticed squeaks from the rear suspension or a slight difference in ride height from side to side, worn factory rubber spring pads are often the culprit. During installation of your new lowering bolts, the original GM rubber pads are removed, making it the ideal time to upgrade to Energy Suspension Hyperflex Performance Polyurethane Bushings.

Unlike aging rubber pads that can crack, compress, and deteriorate over time, Hyperflex polyurethane bushings provide long-lasting durability while helping maintain consistent ride height and suspension performance.

Benefits of our low-profile Hyperflex bushings:

• Improves suspension performance and durability
• Helps maintain vehicle stability during cornering, acceleration, braking, and uneven road surfaces
• Manufactured from Energy Suspension's proven Hyperflex performance polyurethane
• Improves traction, handling, and overall suspension response

The Advantages of Lowered/Adjustable Suspension

A properly lowered suspension can improve both the appearance and driving characteristics of your Corvette. By lowering the vehicle's center of gravity and reducing suspension travel, weight transfer is better controlled, resulting in a more responsive driving experience.

Reduced Body Roll

Lowering the center of gravity helps reduce body roll during cornering, improving steering response and overall vehicle stability.

Improved Ride Height Consistency

Ride height can vary significantly between C4 Corvettes due to model differences, suspension options, mileage, and component wear. We've seen factory ride heights ranging from approximately 26" to 30". Our adjustable lowering kit allows you to compensate for these variations and achieve a more consistent, level stance.

Ideal for Aftermarket Wheels

Aftermarket wheels often increase the visible wheel gap, making ride height adjustment desirable for a cleaner, more aggressive appearance. Whether you're running factory wheels or larger aftermarket combinations, our adjustable kit allows you to fine-tune the suspension to complement your wheel and tire package.

Improved Aerodynamics

Lowering the vehicle reduces the amount of air passing beneath the chassis, which can improve aerodynamic efficiency. General Motors designed the Corvette with a slight factory rake to enhance high-speed stability, and we recommend maintaining that rake whenever possible.

For normal street and highway driving, no additional adjustments are necessary. Vehicles operated at sustained speeds above 130 MPH—such as in closed-course or competition environments—should have ride height evaluated after any suspension adjustment, as with any performance lowering system.

About BDE-Systems LLC

Founded in 2014, Botello Dynamic Engineering (BDE) Systems LLC was established to bring innovative products and solutions to the Corvette community. Based in Ventura County, California, we proudly source our materials within the United States.

As a disabled U.S. Navy Veteran-owned business, we remain committed to quality, innovation, and customer service. A portion of our eBay sales supports the Navy SEAL Foundation and its mission to assist Naval Special Warfare families and veterans.

Thanks to the support of the Corvette community, we have expanded beyond the C4 platform into the C2, C3, C5, C6, and C7 markets while continuing to develop, test, and refine new products using our own Corvette fleet.

Eli Botello
Owner, BDE-Systems LLC