Help! Paint cracked on new rear bumper
 

I had my car repainted a couple months ago and the rear bumper developed two small cracks below the tail lights right before it curves outward. I took the car back to the paint shop, they repainted it, put it back on the car, and it cracked again. They said the culprit was the sharp edges around the rear end of the car were rubbing on the bumper cover, causing it to crack. They said my options were to have them grind down the edges and have them reweld the area to smooth it out. I have a feeling that this is not the solution, unless the car was in a rear end collision prior to me owning it and the repair was done incorrectly. As far as I can tell from the Carfax and the previous owners' records of the car it has not been in a rear end collision, but this is a 26 year car. :biggrin: Is there something missing here? Is this a common problem?
https://cimg6.ibsrv.net/gimg/www.rx7...adf1b004ba.jpg
https://cimg9.ibsrv.net/gimg/www.rx7...ada07e3251.jpg
back side of bumper where the rubbing is occurring.

https://cimg7.ibsrv.net/gimg/www.rx7...a908dcf296.jpg
Bumper is rubbing against these points.

also VERY much more likely is the bumper isnt its original shape anymore causing this issue. the solution would be to get another bumper or have them grind down the edge like they said.

I don't know if this is normal, but I doubt the car would be designed to allow rubbing between the bumper skin and those surfaces as the shop is suggesting. My best guess from your pictures is that some adjustment of the bumper skin relative to the underlying metal structure is necessary to create clearance in those spots. Perhaps the shop can add shims/washers to the bumper skin's mounting studs - then when they fasten it with the nuts, there should be a bit more clearance between bumper skin & structure.

I agree. Or, perhaps they can install a thin but firm sheet of plastic or something over the rub marks on the inside of the bumper to protect it so that those rub points don't dig in. Don't let them grind down factory body metal.

As you said, it’s an old car. Foam shrunk, body flexed a millimeter, and plastic covers change shape or shrink too. And since the car wasn’t hand built those two areas probable had barely enough clearance during original assembly.
If it fit and looked good previously...with the exception of the paint cracking in just those places, then I wouldn’t screw with anything other that the two points indicated by arrows. They are not cosmetic in any way. And if it’s just a couple of millimeters if clearance needed, I actually wouldn’t have issue with tapping them down instead of grinding. It won’t affect crash-worthiness.
The shop probably should have caught it the first time. Glad they’re standing behind it. As much as anything I might be concerned about material build-up on the cover.

pic of the cracks?

Wow! Thanks for all of the replies and suggestions. Unfortunately I do not have any pictures of the cracks. Went over to a friends house and noticed the same issue on his car, just to a lesser extent. I think y'all are right in saying that the bumper overtime has most likely sagged and the foam has compressed. Will be talking to the shop on Monday about more options. Last Friday I gave them the green light to tap the metal edges down with a hammer. If the issue persist I may try to replace the foam. Will keep you updated.

Assuming they are a pro shop and are adding product additive to paint to allow for flex?

Affix some foam on the offending metal underneath and call it a day.

Mine cracked on the raised bumps on either side (The inner arrow on your pic), I think I fitted the bumper too tightly. I resprayed the bumper again and refitted it without pushing it in as far when tightening down the fixing bolts and it has been fine since.