Rear Strut Coil-over Conversion and Load Paths

I am in the process of adapting some ebay coilover sleeves to my Escort ZX-2 rear struts.

In the oem configuration, the main spring force is transferred to the strut mount plate through a rubber isolator and then directly into the chassis. The bumpstop fits inside a ‘cup’ and when active, it acts on the rubber ‘bushing’ section of the strut mount.

If I just use the upper spring perch as-is, all of the spring and bumpstop load will be acting on the rubber bushing section of the strut mount.

Since I don’t want to blow out rear strut mounts on a regular basis, modifying the spring perch so that it acts on the strut mount plate is what I should do, right?

If I also open up the ID of the spring perch, the bumpstop will be able act just like in the oem setup as well.

How do rear strut coil-over setups typically work? Are people running all the load through the rubber bushing section or is this an uncommon configuration?

Pictures for reference:

I think I'd make an aluminum plate (like a great big flat washer) to transfer the spring load to the upper strut mount in the original way.

I'm planning on making it work like the factory setup. I'm mostly wondering at this point if this is something common that is generally ignored or what.

Do I see two springs there ?

iceracer wrote: Do I see two springs there ?

I do.

My KSport RR coilovers have a pillowball mount

Yes, two springs for now. I'm trying to make the crappy ebay kit work for me. Stack two super short, high rate springs and get a useable length with half the rate. When I figure out what actual length and rate I want, I'll go to one spring. I'm only putting coil overs on the rear for now so one ebay kit gives me all four springs.

With the pillowball mounts I'm assuming that all the loads go through the pillowball, correct?

Still wondering if this is something common that is generally ignored or what.

probably generally ignored. are you planning on hitting the bumpstops a lot? unless you're planning on using the bumpstop as part of some kind of progressive rate spring setup, i don't think its going to be an issue so much that you are blowing out strut mounts on a regular basis. i'd worry more about a super stiff shock damping rate blowing out strut mounts before i worried about the bumpstop doing the same.

The concern is that all the coil spring load all the time is being applied to the rubber bushing where previously only bumpstop spring loads were (plus the usual damping force) in the oem configuration.

I guess I need to take a closer look at the actual strut mount and maybe take apart one of my old ones.

This is a cone-squishing rallycross car so its suspension will get more of a workout than typical.

Perhaps you could use a shock mount from a Miata? What is the distance between the 2 studs?

Not sure if that would solve the problem or if it works the same way but it is just a thought.