Black Plastic Bumper Modifications (ABS)

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  • November 17, 2009 at 1:57 am #17015

    Hey Guys,

    I’ve got a later set of bumpers for my current project car and need to shorten the sides a little to match up with some rubber trim that I have on the car already. My thought was to cut the bumper ends, remove the section I don’t need and epoxy/weld them back together.

    Never done it – what is the best way to do this (I’m pretty sure they are ABS – old 80’s Volvo)?


    November 19, 2009 at 6:07 am #17054

    I’m trying Norton Speed Grip epoxy for the first time…it’s drying up in the garage right now. I’ll post more when it’s done.

    November 19, 2009 at 6:13 am #17056

    Thats what I bin using for a while now , but on bumpers I plastic weld when possible. speed stick works ok If you laminate a piece on the back side for strength. Sorry for the late response :blush: was gonna respond a day or so ago and got side tracked and forgot :stoned

    November 19, 2009 at 6:41 am #17058

    As a hack, I like to melt some mesh into the repair, sand the shiney spots and put SEM problem plastic on it.

    November 19, 2009 at 7:52 pm #17070

    I used some aluminum mesh on the backside – they will have to be painted as the profile isn’t perfect (doesn’t have to be for this job) – I don’t have a plastic welder, or I’d try that for sure.

    November 19, 2009 at 8:11 pm #17071

    Take a piece of what you cut off, use a heat gun to melt it and use a screwdriver or similar to spread it out onto the bumper. Being the same material it will make a solid repair. You can even embed mesh in front.

    November 19, 2009 at 11:10 pm #17073

    before I had a plastic welder which is a glorified wood burner kit a soldeiring gun worked not to bad when you got the technique down

    November 23, 2009 at 4:44 am #17149

    Back to the project – I got sidelined with a few other little projects this week and didn’t get back on the job until Saturday. Here’s how I shortened my later bumpers to fit my car (again the idea was to make it fit my existing trim).

    First up, measure the length of the trim and mark it on the bumpers when installed (Yellow marks).
    Rear (going to have to shorten it about 6″):
    Note the rather poor condition of this set of bumpers (they were free).

    Front (better, only 2″ to loose out front):

    Then cut the ends of the bumpers off – a jig saw worked best.

    Then take the cap (this is the rear bumper) and position it to get the correct length relative to the trim line. Then cut back to this point.

    In preparation for epoxy, I roughened up the back side and V’d out the cut line (fitting was completed first) on both parts. I found that my carbide burr left a pretty decent finish for the epoxy.

    Apply the reinforcing mesh. On the front bumpers I used my soldering iron to melt the mesh into the bumper.

    I used foil tape on the back side to keep the epoxy in place.

    The material to stick it back together. Norton Speed Grip Epoxy, reinforcing mesh and applicator. My bodyshop supply pal let me borrow the gun for the night – great guy.

    Finished – set it aside to cure.

    I then used some flexible filler to make the bumpers look a little better. I used this where the bumpers were gouged, or dented. I also filled the license plate screw holes in the front bumper (we don’t have front plates in Alberta).

    The product says it’s fast and it is – open time is about 4 minutes. I counted it down using songs on my radio – only one song’s worth of working time from squeezing it out of the tube to application – you have to move.
    I then sanded out the rest of the bumpers to ensure good adhesion of the bumper paint. Areas that were not damaged were prepared with a burgundy 3M pad.

    Then on with the bumper paint. The first few coats revealed a bit of plastic fuzz in the repair areas – so I sanded it off with 400 wet and dry and shot it again.

    Here’s the finished product. They aren’t perfect as there are many little dings, sandblasting pits etc – but they sure are a lot better than before.

    Close ups:

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