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There are no off-the-shelf coilover options for the rear of my project car (solid rear axle, separate springs and dampers), and I've seen warnings from various car-related forums about attaching a shock/spring combo to the lower shock mount. This seems legit -- it looks a little flimsy to be supporting all that weight:

lower shock mount

But I confess I don't know if that's the only safety concern in terms of points of failure.

Is there any reason I can't just reinforce the lower mount with a bolt-in or weld-in bracket and then use a "real" coilover with it?

Another option would be some kind of axle-mounted bracket:

weld-on axle shock mount bracket

On a related note, this would probably change the mounting angle of the spring/shock by +/- n degrees, so will that also introduce new issues with the top mount? I haven't even done anything yet, and it's already snowballing.

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    I don't think it would be responsible for anyone here to answer this question without far more information regarding specifics of the setup. Your best bet is to consult with an engineer local to you that specialises in these kinds of things. – H. Daun Jun 14 at 2:07
  • That's probably fair. I'm looking more for general approach ideas here rather than just taking the answer at face value and doing something stupid (e.g. "forget coilovers, cut your springs!" CHOP). I will flesh out the question, though. Thank you. – 8bitartist Jun 14 at 5:01
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I am an engineer, and to cut to the chase: No way! It won't handle the forces, the geometry will be completely wrong, and the axle will not be located properly and constantly want to twist.

Your better bet is to figure out a way to incorporate the damper inside of the of the existing spring, and using the lower spring perch already on the axle. Only that area is strong enough and located properly to handle the forces that suspend the vehicle.

Another possibility is to have an expert welder cut away the lower sprint perches on the "donor" axle, and securely weld in the style of brackets you show in your picture - in the exact same place (the fore/aft centerline of the axle). That takes care of the lower coilover mount, but the upper can't go just anywhere and also has to be of suitable strength.

Keep in mind if you are installing a soild axle to deal with a larger engine with more HP/torque, you are also going to need trailing arm(s) or at least a snubber to deal with axle twist - something the factory body/suspension was most likely not designed to handle.

A panhard bar might also be needed to deal with left/right axle shift.

enter image description here

  • Thank you, this is excellent info. So the axle location will be an issue even with the factory 4-link in place? I had the (probably mistaken) idea that the 4-link would determine the axle's center. – 8bitartist Jun 14 at 5:24
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    @8bitartist if the "donor" axle ends up in exactly the same place as the original under load, the location won't be a problem. If the "springing" forces along the new coilovers act in roughly the same trajectory as the original coil springs, that too will not be a problem. Without seeing your project, I find it doubtful. You can't shift the "suspending" outboard of the front-rear centerline of the donor axle without imparting huge twisting forces other components won't be able to deal with. It's why the donor axle has the lower coil spring perch exactly on top of the axle. – SteveRacer Jun 18 at 2:09
  • That makes a lot of sense. I hadn't considered all the effects changing the spring trajectory would cause. I think considering my experience level (low), leaving the existing mounts and suspension geometry where it is and just finding a way to source shorter springs and/or struts for the OEM perches is going to be the path of least resistance here. – 8bitartist Jun 20 at 0:21
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    @8bitartist There is certainly an advantage to a "coilover" type suspension, for the reasons I discussed. The spring compression and damper trajectory are absolutely equal, since they share the same axis. Your latest plan sounds the most prudent, and will get your project on the road safely a lot sooner I suspect. Good luck! – SteveRacer Jun 20 at 3:04

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