bumper issue

[Belgian1979vette]

I have bumped into the following problem when replacing my damaged rear bumper. The replacement actually doesn't seem to tighten up to the fiberglass as the original did. After some research I've found that the factory bumper seems to have a ridge right on the outer edge of the bumper that is exactly the hight of the metal retainers normally sitting in between the bumper and deck.

The replacement doesn't have the ridge, so the metal keeps the bumper from contacting the fiberglass completly.

I've also ordered and used the aftermarket type of retainers that only have a rear supporting bar with thru bolts, but even with those the 2 parts do not completly contact. There is Always a gap of about 2 mm.

Any ideas ?

 

[DeeVeeEight]

I have bumped into the following problem when replacing my damaged rear bumper. The replacement actually doesn't seem to tighten up to the fiberglass as the original did. After some research I've found that the factory bumper seems to have a ridge right on the outer edge of the bumper that is exactly the hight of the metal retainers normally sitting in between the bumper and deck.

The replacement doesn't have the ridge, so the metal keeps the bumper from contacting the fiberglass completly.

I've also ordered and used the aftermarket type of retainers that only have a rear supporting bar with thru bolts, but even with those the 2 parts do not completly contact. There is Always a gap of about 2 mm.

Any ideas ?

I gave up and filled the gap, it was a pita to try and keep the seam looking uniform.

 

[MYBAD79]

Don't place anything between the two parts and try to tighten it that way.

Another (painful) approach is to use masking tape on the body surface, then apply some urethane putty (bumper repair epoxy) to the mating surface of the bumper and install it against the taped surface. The tape will prevent the bumper to stick to the body... Let it cure, remove bumper, sand , prime, paint ....

 

[damoroso]

I found the retainers limited how much you can move the bumper covers, so I left them out. Also at least on the 80-82's, the retainers go behind the bumper, and behind the fiberglass, so you have the fiberglass and urethane touching each other directly. Karsten's right, nothing should be between the parts. Oh, and if you can do it in the sun or under work lights to help soften it a bit, it helps too.

 

[Belgian1979vette]

At this point there is nothing in between them, with the aftermarket retainers.

I cannot fill the gap as I would need to fill the bumper. I can hardly see anything hold onto it in that location.

 

[damoroso]

Can you post some pics?

 

[68/70Vette]

I have bumped into the following problem when replacing my damaged rear bumper. The replacement actually doesn't seem to tighten up to the fiberglass as the original did.

Any ideas ?

Details about where the replacement came from. I know that some repro front bumpers don't fit. I bought one on ebay...looked beautiful, nice chrome, etc...but it didn't fit. I bought some rear bumpers from Paragon last year, haven't tried to mount them...they're supposed to be GM authorized parts. Actually I would have bought a front repro bumper from Paragon, if I knew it was one that would really fit. I have a couple of stock front bumpers that I can have replated to fit...but replating here in So Cal is just sooo expensive. The guys that do my replating plead mercy...they say the EPA has increased their operating expenses. For a small shop, they pay $40,000 in January for EPA licenses. They actually have some EPA waivers due to grandfathering....but if they sell their plating business, the waivers will not transfer. Essentially, they cannot sell their business. When they retire, their business becomes worthless.

 

[MYBAD79]

I cannot fill the gap as I would need to fill the bumper. I can hardly see anything hold onto it in that location.

I guess in other words: use masking tape on the body mating surface, roughen up the mating surface on the bumper, then bolt up the bumper as it is but use longer bolts that allow you to have a 5mm gap..... put some 3M 8115 or equivalent in that gap, tighten up the bolts, let the glue cure.... unbolt and remove the bumper.... remove or cut the excess glue, .... now your bumper is contoured to fit your body....

not saying you should just fill the gap, but re-shape the bumper to fit your body....

hope this makes more sense....

 

[Belgian1979vette]

Couple of things :
- car is in the body shop, so I cannot take pics at this moment.
- I have terrible experiences with the 8115 beneath paint (swelling in sunlight problem).
- Bumper is supposed to be an GM replacement from Eckler's. For the rest it fits as it should.