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Thread: Top of the rear shock support looks odd...

  1. #1
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    Top of the rear shock support looks odd...

    I recently put in KW coil-overs. They're working well, although it seems like a rear passenger side bushing is squeaking. While looking at them, I noticed this bit of weirdness.

    This is my rear driver's side:

    IMG_9997.jpg

    And here's the passenger side.
    IMG_9998.jpg


    The driver's side is recessed, and the passenger side is bowed upwards. This seems bad. My question is, how bad?

    Thanks!

    -- Joe

  2. #2
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    I pulled the shock, and it doesn't look good...

    IMG_0005.jpg

    Since I would prefer not to replace my frame, I'm thinking of something like, say, getting some half-inch steel plate and welding it in. It won't have the curved support that the original did, but it'll be so thick that it probably doesn't matter.

    Any thoughts on this idea, or other solutions to repair this?

    Thanks!

    -- Joe

  3. #3
    Senior Member Bitsyncmaster's Avatar
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    I would think a 1/4" steel plate would do.
    Dave M vin 03572
    http://dm-eng.weebly.com/

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    DMC Midwest - 815.459.6439 DMCMW Dave's Avatar
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    Quote Originally Posted by Bitsyncmaster View Post
    I would think a 1/4" steel plate would do.
    Considering that the entire frame is pretty thin, 1/4" would be overkill. Might also cause you to split the bushings.

    Also try not to upset the geometry too much i.e. such that the top of one shock is higher than the other. This wouldn't be a big deal with the original springs, but if your coil overs support the top of the spring on the shock itself it would be somewhat critical to avoid having one corner of the car sprung different from the others. IF that is the case you probably need to reinforce the top plate on both sides of the car.
    Last edited by DMCMW Dave; 09-15-2023 at 12:59 PM.
    Dave S
    DMC Midwest - retired but helping
    Greenville SC

  5. #5
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    I'll get some 1/4" and 1/8". I'm sure I'll find some use for the other piece.

    I was going to try to hammer down the top that was buldging upward, but I can't fit a hammer in there, and I don't feel like removing the body. My current plan is to try to crush it down by drilling a hole in the middle of the two plates and using a large bolt to compress them and hopefully flatten the bulge.

    A friend suggested it's probably not worth the trouble to weld the plate in either, but rather just drill some holes and bolt it in place. I'll just have to see how hard it is to drill through that part of the frame with a power drill (I can do the plates on the drill press).

    I was thinking of putting plates on both the top and bottom, but maybe that's overkill too.

    Dave W, you're right about the coil-overs -- the top is supported by the top plate. So I may indeed be doing both sides. Which probably isn't a bad idea.

    Thanks!

    -- Joe

  6. #6
    DMC Midwest - 815.459.6439 DMCMW Dave's Avatar
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    TBH I've always been a bit skeptical of coilovers for this reason - you are supporting the weight of the car on things that weren't designed for it. In the back, this part. It should be part of the installation to weld or bolt reinforcing plates to the frame, preferably on the inside rather than above. Unfortunately, doing it on the inside also means dealing with the depressed area that in your case became inverted.

    In the front, the original spring design has the springs on the round perches spread across a relatively wide part of the lower control arms. With coilovers, the entire front weight of the car is supported on the lower shock bolts which were only intended to carry the dynamic load of the shock absorbers, and only on the sides of the arms in a pretty concentrated area. I'd expect that, if you are converting to front coilovers, you really ought to be beefing up the sides of the lower control arms or converting to something aftermarket that is a bit stronger in this area.
    Dave S
    DMC Midwest - retired but helping
    Greenville SC

  7. #7
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    The good news is that I put in billet aluminum lower control arms and adjustable uppers in the front, so I do have the front reinforced as well. Good point about the difference between coil-overs vs separate shocks and springs with regards to cars like ours that weren't explicitly designed for them.

    As for the rear, to increase the strength of that rusted-out area, I'm going to add some thick washers. The goal here is just to make it less likely for the center of the steel plate to flex inward, although I'm not sure I really have to worry about that. The KW coil-overs don't actually seat there, instead using large truncated conical pieces that distribute the force around the edges similar to the springs original springs, but the shock itself is still bolted through the center, so it can't hurt to have the extra reinforcement.

    -- Joe

  8. #8
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    Since the frame was made of 16 GA mild steel (around 0.052"), 1/4" (0.250") would be a lot more than you need. More important than thickness, you need to add gussets and angles to help distribute the load over a larger area of the frame.
    David Teitelbaum

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