An old saying declares that “doing the right thing never goes out of style.” The issue here is determining what the right thing is. If you interviewed every shop in the country and asked if they always do the right thing when it comes to repairs, certainly a hundred percent would say they do. Yet, findings from an I-CAR report just a few years ago indicate that over half the industry doesn’t stay up to date with training, instead getting by with previous education, hoping that it will prepare them to fully restore new model vehicles to pre-accident condition.
These hopes simply aren’t enough to prepare shops to handle the repair instructions and recommendations that are often updated from one model year to the next—sometimes during the year. No where is this truer than with bonding.
Modern vehicles use full range of bonds from welds to rivets and adhesives. How these bonds are applied can vary greatly from one vehicle or application to the next. If your shop isn’t aware of updates, it risks creating bonds that not only won’t hold up during the life of the vehicle but could prevent critical safety systems from performing as they should during another accident.
The following repair steps and guidelines, submitted directly from General Motors, serve as reminders of (1) the sophisticated steps necessary to make bonds for today’s vehicles, in this case rivets on a 2019 Chevrolet Silverado, and (2) how recent OEM recommendations on bonding products can make a noticeable difference on a repair. Review both and consider how your shop is adapting to the latest directions and guidelines for bonding.
Rivet roundup
Refer to the following repair procedure provided by GM, taking special notice of where, when and how rivets are used. Also note the need to turn to other GM repair procedures during this work to ensure the job is performed correctly.
Removal Procedure
Before beginning, refer to the following GM documents:
- Approved Equipment for Collision Repair Warning
- Collision Sectioning Warning
- Glass and Sheet Metal Handling Warning
Note: The that the front end is constructed from high strength low alloy steel. Refer to GM’s High Strength Low Alloy Steel procedure.
- Disable the SIR system. See GM’s SIR Disabling and Enabling procedure.
- Disconnect the battery negative cable. See GM’s Battery Negative Cable Disconnection and Connection procedure.
- Remove all related panels and components.
- Remove both front fender bracket. See GM’s Front Fender Bracket Replacement procedure.
- Remove both front fender rear bracket. See GM’s Front Fender Rear Bracket Replacement procedure.
- Remove the sealers and anti-corrosion materials from the repair area as necessary. See GM’s Anti- Corrosion Treatment and Repair procedure.
- Perform a rough cut through the inner and outer rails in line with the center of gauge hole. Note: All cuts must be square to the surface.
- Remove the front-end section from the vehicle.
- Remove front compartment side rail bracket – rear right. See GM’s Front Compartment Side Rail Bracket Replacement – Rear procedure.
- Remove front compartment side rail bracket – rear left. See GM’s Resistance Spot Welded Full Panel Replacement procedure. Note: Do not damage or cut attaching panels and reinforcements.
- Remove all spot welds from the outer side rail.
- Apply heat to release adhesive from the outer side rail sectioning.
- Remove outer rail sections from the vehicle. Note: Do not damage or cut attaching panels and reinforcements.
- Remove all spot welds from outer side rail reinforcement.
- Apply heat to release adhesive from the outer siderail reinforcement.
- Remove the outer rail reinforcement. Note: Do not damage or cut attaching panels and reinforcements.
Note: Drive side rear bulkhead will remain on vehicle while passenger side rear bulkhead will be replaced with the new front end. Note: All cuts are square to surface.
- Cut the inner side rail at the appropriate location.
Note: Do not damage or cut attaching panels and reinforcements.
Note: All cuts must be square to the surface.
Note: The drive side rear bulkhead will remain on vehicle while passenger side rear bulkhead will be replaced with the new front end.
- Cut the inner siderail at the appropriate location.
- Remove inner rail sections from the vehicle.
- Remove remaining adhesive from vehicle.
Installation Procedure
Note: The new front end will come with a support bar bolted to the rear of the inner rails to ensure stability during transportation. Make sure to remove this bar prior to installation.
Note: The rear top portion of outer rail will be pitched upward for ease of install. Ensure that it is repositioned properly and welded accordingly during the installation.
Note: Slight modification of the passenger side rear bulkhead tabs inward will be required to allow for proper installation of the front end.
- Temporarily install the front end for proper fit. Position the front end to the vehicle using 3-dimensional measuring equipment.
- Temporarily install the radiator support body mounting bolts to ensure proper alignment.
Note: The new front end will come with pre-drilled holes on the outer side rail to allow for proper alignment of front end.
Note: The 6.7 mm (17/64 in.) holes will be used for rivet installation.
- Drill 6.7 mm (17 / 64 in.) holes through the outer side rail for rivet installation.
Note: The new front end will come with pre- drilled holes on the inner side rail to allow for proper alignment of front end.
Note: The 6.7 mm (17/64 in.) holes will be used for rivet installation.
- Drill 6.7 mm (7/64 in.) holes through the inner side rail for rivet installation.
- Remove the front end and radiator support body mounting bolts from the vehicle.
- Temporarily install the rear rail bracket for proper fit. Position the rear rail bracket to the front end using 3- dimensional measuring equipment.
- The rear rail bracket will be located 24 mm (0.9 in.) from the inner side rail sectioning mark. Note: The 6.7 mm (17/64 in.) holes will be used for rivet installation.
- Drill 6.7 mm (17/64 in.) holes through the rear rail bracket for rivet installation. Note: The 6.7 mm (17/64 in.) holes will be used for rivet installation.
- Remove the rear rail bracket from the front end.
- Drill 8 mm (5/16 in.) plug weld holes on the rear rail bracket.
- Apply GM-approved Weld-Thru Coating or equivalent to all welding surfaces. See GM’s Anti-Corrosion Treatment and Repair procedures.
- Clean and prepare side rails and vehicle for adhesive according to adhesive manufacturer’s recommendations. See GM’s Metal Panel Bonding procedures. Note: Only remove E-coat where adhesive will be applied.
- Apply structural adhesive on the mating surfaces of side rails and vehicle according to adhesive manufacturer’s recommendations. See GM’s Metal Panel Bonding procedures.
- Apply structural adhesive on the mating surfaces of the rear rail brackets according to adhesive manufacturer’s recommendations. See also GM’s Metal Panel Bonding procedure.
- Install the front end to vehicle and clamp into place.
- Install the radiator support body mounting bolts to ensure proper alignment.
- Install rivets in the appropriate spots on the outer side rail. See GM’s Fastener Specifications procedure.
- Install rivets in the appropriate spots on the inner side rail. See GM’s Fastener Specifications procedure.
- Install rear rail bracket to vehicle and clamp into place.
- Install rivets in the appropriate spots on the inner side rail. See GM’s Fastener Specifications procedure.
- Install rivets in the appropriate spots on the outer side rail. See GM’s Fastener Specifications procedure.
- Reposition the outer rail as necessary to align front end to vehicle.
- Perform spot welds on the outer side rails.
- Perform MIG/MAG welds on the rear rail bracket.
- Install the front compartment side rail bracket – rear left. See GM’s Resistance Spot Welded Full Panel Replacement procedure.
- Install both front fender rear brackets. See GM’s Front Fender Rear Bracket Replacement procedure.
- Install both front fender brackets. See GM’s Front Fender Bracket Replacement procedure.
- Install all related panels and components.
- Apply the sealers and anti-corrosion materials to the repair area as necessary. See GM’s Anti-Corrosion Treatment and Repair procedures.
- Before refinishing, refer again to GM’s Anti-Corrosion Treatment and Repair procedures.
- Paint the repaired area. See GM’s Basecoat/Clearcoat Paint Systems procedures.
- Connect the battery negative cable. See GM’s Battery Negative Cable Disconnect ion and Connection procedure.
- Enable the SIR System. See GM’s SIR Disabling and Enabling procedure.
Rethinking structural adhesives
Applying structural adhesives is easy; just apply to the repair area like any other adhesive and follow the proper cure time, right? Wrong. Without training and using the OEM repair instructions, you’re almost guaranteed to botch this work. Along with always following these instructions, GM provides the following recommendations.
Rule 1: Use structural adhesives wherever any adhesive needs replaced.
For GM vehicles, use structural adhesives for all adhesive repairs with one exception—replacing the adhesive used on door skins. GM says there’s good reason to stick with super-strong adhesives instead of using multiple glues. Doing so will help you avoid using a non-structure adhesive where one is needed, a serious mistake that can affect how a vehicle handles and responds significantly. Further, structural adhesives provide the strongest possible bond. It only makes sense to use them wherever possible.
Rule 2: A mechanical bond is mandatory
Structural adhesives can’t do their job alone. Without exception, a mechanical bond of some type—a weld, rivet, screw, etc.—also must be incorporated.
Rule 3: No MIG Plugs
MIG plugs must NEVER be used with structural adhesives since they can damage the adhesive bond. GM declares that properly cured structural adhesives work extremely well with resistance spot welding. Where a spot weld cannot be applied, use structural rivets or flowform screws instead.
Rule 4: Use only recommended structural adhesives
When structural adhesives first made their appearance in new vehicles, shops were limited in their options. With more choices available today, it’s more important than ever for repairers to find the one approved by an OEM for specific work. Not all structural adhesives are created alike. Using the correct option and applying it with the recommended application steps is critical in creating an OEM bond.
Doing anything less can mean returning an unsafe vehicle to a customer or at the very least one that no longer rides, performs or handles certain sensory information—such as wind and road noise—as it once did. Customers might very well notice the difference.
Their safety and satisfaction, as with any other type of repair work, is ultimately a result of doing the right thing.
