by Hib Halverson
When GM was developing the C7 Corvette platform back in the early 2010s, one goal was stiffening the car’s structure, suspension and steering. If you’re under a C7, one of the first things you notice are the aluminum “underbody braces” that tie the perimeter frame rails to the suspension cradles. Those braces were a result of meeting that “enhanced stiffness” goal.
Back in the day, for parts like those braces, GM used steel. However, as a weight reduction move, the Corvette Team designed aluminum braces. They offered an improvement in rigidity of the front and rear structures over no braces at all but, they were of marginal stiffness in bending. GM also considered braces made of composites and met with Glasforms, a manufacturer of composite parts, but learned that a challenge with a composite brace was optimal mechanical properties in torsion, compression and bending.
The C7 eventually went into production with the aluminum braces. They are cut out of 0.250-in. aluminum stock then finish-machined such that the fronts are 25-in. by 1.1875-in. and the rears are 22.1875-in by 1.375-in. They are drilled on one end but slotted on the other and attached with bolts. The front braces are held with a bolt at each end and the rear braces use one bolt in the frame and two in the rear cradle.
GM continued discussions with Glasforms and eventually decided to pursue carbon fiber/epoxy composite braces made by “pultrusion”, a process which draws resin-coated carbon or glass fibers through a heated die. Pultrusion offers a constant cross-section and good longitudinal fiber alignment but has limited strength in bending. Glasforms then hit on a design with pultruded, unidirectional carbon fiber and a transverse engineered fabric which offered 50% better strength in bending compared to the aluminum parts. The resulting brace assemblies are also about 10% lighter than the aluminum parts.
Prototypes were delivered to GM for vehicle shake and road testing. They were validated and now are an aftermarket upgrade for the C7 Corvette available as Chevrolet performance parts called 2014-2019 Z06 Carbon Fiber Underbody Chassis Braces (PN F-807) and sold by Zip Products.
01: Installing the CF underbody braces is pretty easy. Start with the two front braces. In some cases, such as some Grand Sports, most ZO6s and all ZR1s, you’ll need to drive the front of your C7 up on a pair of low ramps before you can get a floor jack under your front air dam or splitter. We used a set of Race Ramps which raise the front end three inches and are made with “stops” which prevent the front tires from inadvertently rolling off the end of the ramp. Once the front wheels are on the ramps, set the parking brake.
02: Put an 18-in. long 2×4 on the jack pad then roll the floor jack such that your 2×4 is under either of the front suspension cradle’s crossmembers. Lift the front end high enough for you to work under the car. DO NOT put any part of your body under any part of the car until it’s supported by jack stands.
03: Insert two Zip Products 2014-2019 Billet Aluminum Jack Pads (PN X-3197) in the slots just behind the wheels, then lower the floor jack so the jacking pucks sit on the jack stands.
04: The bolts holding the aluminum braces take an 18-mm, 1/2-in-drive socket on either a 1/2-drive ratchet or a 1/2-drive impact gun. Loosen the bolts on the slotted end of the braces and remove the bolts from the other ends. Remove the braces by sliding them out from under the bolts in the frame rails.
05: The Chevy Performance Carbon Fiber Underbody Chassis Braces come with new bolts, so pick two of the new bolts and install each brace. Position it such that each bolt is centered inside the metal overlays on the end of each brace. This ensures that bolts apply clamping force evenly to each end of the brace.
06: Use a torque wrench to tighten all the bolts to 74-ft/lbs.
07: Set the front end back on the ground, put wheel chocks in front of the front tires, then roll your floor jack around to the rear.
08: Depending on the height of the jack, you may or may not need to drive the rear wheels up on the Race Ramps. Roll the floor jack under the back of the car such that the 2×4 block is under either of the rear suspension cradles two crossmembers, then jack the car up high enough to work under. DO NOT put any part of your body under any part of the car until it’s supported by jack stands. Insert two jacking pucks in the two slots on the frame near the wheels then lower the jack to set the jacking pucks on two jack stands.
09: Loosen the bolts on the slotted end of the braces and remove the the four bolts from suspension cradle ends of the braces. The Chevrolet Performance CF rear underbody braces only take two bolts on the suspension cradle ends so discard two of the bolts you removed. Remove the braces by sliding them out from under the bolts in the frame rails.
10: The CF braces come with new bolts, so pick two of the new bolts and install each brace. Remember to position the braces such that the bolts are centered on the metal overlays. Use a torque wrench to tighten the bolts to 74-ft/lbs.
11: Set the rear end of the car back on the ground, remove the front wheel chocks and go for a test drive.
2014-2019 Corvette Carbon Fiber Frame Brace Install
Source: Zip Corvette Parts
8067 Fast Lane | Mechanicsville, VA 23111 | (800) 962-9632
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