Repairing cracked paint on a plastic bumper?

Discussion in 'Compounds, Polishes, Paint Cleaners, and Glazes' started by krshultz, Mar 16, 2010.

  1. krshultz

    krshultz Nuba Guru

    Hey gang -

    As I think most of you know, I autocross my Honda S2000. A lot. Over the course of hitting the occasional cone at speed, the front bumper takes a serious beating. It has been repainted twice, and in spots, the paint is cracking from the bumper itself flexing on impact. I am wondering if there is any way to fix it. Here are two photos:



    Apologies for the photos, hopefully, you can see what I'm talking about. It was very difficult to catch the cracks in a photo.

    I can barely feel the cracks with my fingernail, which leads me to believe that they're in the clear coat. I'm considering trying my luck wet sanding them out. I'm also thinking about maybe masking off the surrounding areas, and shooting the cracks with a tiny amount of clear, to maybe fill them in a bit. That's a bit outside my experience level though, I've never really worked with *adding* paint to a vehicle. Only in removing it. :)

    Have any of you ever addressed something like this?
  2. Misha

    Misha Nuba Guru

    intrested in same thing. have cracks on back bumper

    problem is it in paint coat which is under clear if im not mistaken so it might not be possible to fix without repaint or wetsanding through clear and then respraying?
  3. pektel

    pektel DB Forum Supporter

    IME, cracked paint is not repairable.
  4. billyblooshoes

    billyblooshoes DB Forum Supporter

    Chances are the clear is cracked all the way through. The fractures cannot be repaired with correction. Since its a smaller area that's affected, a body shop should be able to sand down that area, respray it, and then blend it in.

    Edit: since the plastic of the bumper flexes on impact and the paint and clear are non flexible but bonded to the plastic, worst case is that the clear, paint, and primer are all fractured. Either way, its the same fix.
  5. togwt

    togwt Nuba Guru

    Agree- sounds like a repaint with a flex addative included in the paint
  6. christian900se

    christian900se Obsessive Detailer

    It is most likely a repaint, but I would try wetsanding and polishing because you really don't have anything to lose at this point.
  7. krshultz

    krshultz Nuba Guru

    Billy - that area in the one picture is a small one, but there are others. A second one appeared after last weekend's SCCA National Tour event that is much larger. It spans the full width of the air intake, down low, closest to the ground. Those pictures are simply the two I got that captured some of the cracking. It's all over the place. :(

    Christian - yeah, that's the direction I'm leaning in at the moment.

    What I need to do is find a different body shop. I've had nothing but problems with the guy that did this. He wouldn't stand behind the work the first time it cracked - something about "I can't do anything about it if you're going to autocross the car." I instructed him to reinforce the back side of the bumper with some resin, to stiffen it up and maybe prevent the thing from bending. Well, I had the bumper off recently for a different project, and he didn't do it. So I paid him an hour and a half of labor for him to not do anything. :shakehead: He's a well regarded guy within the local motorsports community, so it was real disappointing to find that he'd half-assed the work.
  8. wagonproject

    wagonproject Jedi Nuba

    Paint will only crack if something strikes it, if you dont beat it around it wont fail, putting additive in paint on a flexible surface that takes quite a bit of abuse (such as front airdams) wont stop the paint from cracking.

    Flex is only temporary, it's used for installing flexible items on a vehicle. It gives the installer an extra big window of pliability when handling bumpers. It has no lasting properties.....the ppg tech sheets state "flex is not needed if item is already on the car" I use to just spray it on front bumpers due to the boss but since a long time I haven't used it once. Clear stays decently flexible for about 5 days after spraying.
  9. Denzil

    Denzil Guest

    Oh, I thought flex was a permanent property when it's applied with the paint. I didn't know paint could still crack from the paint flexing so much.
  10. kustomizingkid

    kustomizingkid Nuba Guru

    I don't understand why you don't clear bra that mofo... or add a co(w)ne catcher... lol
  11. agpatel

    agpatel OD On Detailing

    Talked to my dad about this, works in industry, flex agent can only do so much...yes it can bend but paint does not do well in impact forces. If the crack is only in the clear, he said it was pretty rare as it is normally a wet on wet painting so they become on almost, then you can sand down and spray clear and fix it somewhat...if through base coat then not fixable. You can sand down that are and primer, base, clear then blend and come out well...this is what I did on my rear bumper and came out perfect.
  12. krshultz

    krshultz Nuba Guru

    Yeah, I know, I probably should. Lots of reasons why I haven't. A clear bra didn't seem like it would solve the problem. The paint is flexing with or without a clear bra over top of it, so it seemed to me like it wasn't a solution to the problem. Second, this particular bumper has been pretty torn up for a while now, so it seemed like a waste. Last time I had it painted (after a tire carcass incident on the highway), the insurance company wouldn't pay for a new bumper. So I guess I figured I'd eventually have to scrap it anyway. It's getting to that point now.

    There's also the problem of cost. A clear bra install would be several hundred dollars, and when the dollar figures get into that territory, I have to consider my tire budget. Nevermind that said money could, eventually, go towards having some paint work done on the car at a proper body shop.

    Stupid hobby. You're right, I know you've suggested the clear bra route before, and it would certainly keep parts of the car from getting worse than they are. When money gets a little less tight, I'll consider it carefully.
  13. kustomizingkid

    kustomizingkid Nuba Guru

    Win the lottery?
  14. edwinbong

    edwinbong DB Forum Supporter

    get a bumper dedicated for autox?
  15. krshultz

    krshultz Nuba Guru

    Actually, that was my plan. When the insurance company fixed the last one due to a non autocross incident (tire carcass on the highway), I tried to get them to pay for a replacement bumper cover. They declined the request. I was going to use the old (current) one for autocross purposes, and keep the new one for the winter months.
  16. detailjohn

    detailjohn Detailers Advertising Scheme

    It will definitely be a repaint, but you may be able to get away with a blend repair since it's so low on the car, and silver is fairly easy to blend. But if you're going to race it, you gotta put a clear mask on.

  17. edwinbong

    edwinbong DB Forum Supporter

    thats how i ran my car during autox events. just swapped to a junk bumper and when i got back home, switch back.
  18. agpatel

    agpatel OD On Detailing

    So I was in my design meeting this morning and we were talking about how add some padding to a rod and thought about using pipe insulation, this made me think of you Karl, haha. How about putting it on the bottom lip, it has a slid cut down the side, and gives a little extra cushion to absorb some of the impact and this MAY help your issue. It would also make your s2k one of a kind at the events :lol:


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