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Thread: Cracked Lower Bumper

  1. #1
    Administrator thegunguy's Avatar
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    Cracked Lower Bumper

    Like everyone here, I'm super cautious with not pulling in too far over the concrete space separator when parking the car, but despite my care, it seems that I drag the bumper every now and then. You know you've done it.

    Here's a shot of my latest repair form this afternoon.

    The design of the lower bumper and the aero fences on the bottom of either side seem to inelegantly point out that BMW does not have deep expertise in making low slung cars. For one, what idiot chose yellow plastic that just screams any time you pop off some paint or scuff the bumper? I'd much rather have replaceable piece that is designed to wear like the rubber strip on the bottom of Porsche's cars.

    I wonder if it would be a bad move to shave off the air fences (what always catches and cracks) and coat the bottom of the bumper with a layer of spray rubber, similar to what is used in truck beds. It would seem like this would 1) eliminate the problem area and 2) provide for some protection. The question is if there is a downside to changing the air flow around the tire. This might induce some front end lift, increase fuel consumption (yawn), or reduce brake cooling.

    Anyway, this isn't the first time I've done this repair, nor will it be the last. I just wanted to gripe.
     
    thegunguy

  2. #2
    Z8 Guru 2112's Avatar
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    What adhesive are you using?
    .
    2000 Red over black
    heavily modified for performance. Although, not to the level of GM's car

  3. #3
    Administrator thegunguy's Avatar
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    I just grabbed what I had on hand - Gorilla Glue. I'm not crazy about how much it expands, but if you use very small amounts it's not an issue. It seems to hold well.

    I'm not sure if it's water proof, but that's not much of an issue.

    I'm about to do my seat backs (again). I'm going to try that MXBON 105 stuff.
    thegunguy

  4. #4
    Team Z8 KenZ8's Avatar
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    There is an epoxy sold at body shops and Lowes/Home Depot that is specifically made for the new automobile bumper plastic materials. It is fast setting and remains slightly flexible and waterproof.

  5. #5
    Administrator thegunguy's Avatar
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    Thanks for the tip. I'll check it out for the next time. I wonder if it's for just joining parts or if it's designed to fill so that you can sand and paint. For these repairs, I just want something that has a good bond, not bond plus fill.

    I ordered some of the MXBON 105 to fix the seats. I think it'd be good for this repair too.
    thegunguy

  6. #6
    Team Z8 KenZ8's Avatar
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    It's "carvable" with an exacto blade when set, sandable, and accepts paint or a "Sharpie" which by the way matches the black area perfectly.