Corvette’s new rear bumper features carbon-fiber beam
The 2020 Chevrolet Corvette C8 introduced itself this spring as a powerful, premium mid-engine sports car with several unique features that befit its complete redesign.
One such component is the vehicle’s rear bumper impact bar, which is made entirely of carbon fiber.
The rear bumper impact bar is the first major structural component on the Corvette to be made solely of carbon fiber, which presents its own unique set of repair concerns and challenges.
REPLACE INSTEAD OF REPAIR
General Motors recommends that any structural carbon fiber component be replaced, rather than repaired, should it be damaged in any way. In terms of the rear bumper impact bar, there are two specific repair procedures (and two associated part numbers) to select from, depending on the level of damage. This relates to whether just the rear bumper impact bar (Service Information Document ID: 5541003) or the rear compartment panel (SI Document ID: 5409318) needs to be replaced.
When removing just the rear bumper impact bar (without tub replacement), locate the cut line on the inner tub floor and then cut an access hole to reach the hidden flow drill screw. After cutting access openings in the rear bumper impact bar, apply heat to the inner underside of the bumper to release any adhesive, taking care not to drive heat into any undamaged components.
With both types of procedures, the installation process involves positioning the rear bumper impact bar on the vehicle using three-dimensional equipment, drilling pilot holes to install flow drill screws, and cleaning and preparing the mating surfaces for adhesive application on the structure and the replacement part.
STICKING WITH THE PLAN
Applying the adhesive differs by procedure. When replacing the rear bumper bar, both procedures require aluminum structural adhesive. When replacing just the bar without the top brackets (Part #84711557), it’s necessary to employ a special GM Structural Carbon Fiber Adhesive Kit.
This kit includes a 50ml cartridge of Crestabond M7-05 and a dispensing gun. The Crestabond M7-05 is a Methyl Methacrylate adhesive that bonds with a wide range of composite materials and has a working time between 4 and 7 minutes.
With both procedures, install flow drill screws (using the access hole without tub replacement), apply the proper sealers and anti-corrosion materials, NEVER paint the carbon-fiber beam, and reassemble panels and components using GM Genuine Parts in conjunction with GM repair methods to preserve bumper system performance.