Pascal, did you figure out what your 5in fr spring rates were?

I think the springs in my notchback road car are overload coils in the rear and some trimmed Buick springs in the front. Never been in a rally car but seemed like they would work well.

Luke did some calcs a few years ago and found these springs were pretty much the same as the S&R springs with one coil cut off. I forget if I cut one or two off

https://www.moog-suspension-parts.com/moog-cc653 At the time I think I got a pair of them from Rockauto for $57/pair.

These were the rears:

https://www.jegs.com/i/Moog/719/CC205/1 ... CoQAvD_BwE

Rear
https://www.rockauto.com/en/parts/moog, ... pring,7512

Front
https://www.rockauto.com/en/partsearch/?partnum=CC653

Interesting. So, those look like about the same spring rates I've seen floating around, although the fr's would have gone up a bit if you cut a coil off. If I go the route of modifying the lower perch, these are available between 400-500lb spring rates. Free height is a little shorter than an SPG spring, but if you added a spacer to get it back even and then the higher rate should net additional ride height.

https://www.speedwaymotors.com/Hyperco- ... 444181-475

I got excited when I found d the spring sliders because it seemed like a way to more easily run coil over springs without having to go crazy on the shocks

Did you finish the fab for those? I like that idea too. Maybe that will be phase 3.2

No didn’t finish. Whole car is waiting patiently.

Was trying to design a bracket for the upper a arm so that the spring slider lower mount was as low as possible. So that the upper mount didn’t need some crazy tower for mounting. Then it could be a much easier install, allow for more spring options, easier spring changes, and adjustable preload.

Inner drivers: I remember you told me that when you did a post-mortem on that inner driver that we broke at NEFR you found out that the driver that broke was 3/8" (10mm) shorter than the driver on the other side. I never found out why there would be different lengths (left vs. right?, 99 vs. 900? manufacturing error?)
The inner driver that I broke at that rallycross all those years ago was a result of the front motor mount coming out of the frame mount and the engine bouncing around in the engine bay.

Hydraulic Bump Stops: You could replace the old rubber bump stops with the hydraulic bump stops. They're not super expensive at around $200 (though they're expensive compared to cheap chunks of rubber). I think they're expensive when they're built into a full strut assembly, but since we have a separate shock and spring we can fit a separate bump stop, too.
They're basically an additional progressive-rate shock absorber for the suspension system that only comes into play as the suspension nears the end of its travel. They're soft in the first 1/3 of travel, they get stiffer in the middle 1/3 of travel, and get much stiffer in the last 1/3 of travel. They're user adjustable (the user inflates them with nitrogen) so you have to tune the stiffness. I think they'd make a big difference in the way the car handles the big bumps.

In the image above you'd be putting the hydraulic bump stop inside the spring. The bump stop would need to attach through the spring tower and hopefully tie into the cage.

Springs: There are online spring rate calculators that you can use to get a fairly close calculation for the spring rate. You need to take some measurements (wire diameter, coil diameter, # of coils, shape of the ends of the coils, etc.) and plug that into the calculator.
https://www.thespringstore.com/spring-rate-calculator.html
Somewhere around I have an excel spreadsheet of 99/900 spring rates based on calculations I did at one point (manually). I'll have to see if I can find that.

The springs on Seth's 2dr that he posted links to (a Moog front spring and an overload rear) made the car quite tall and stiff. Mike, you drove it for reccee one year with the three of us in the car. We had a lot of ground clearance. I don't know what the rates were but it felt good from the passenger's side.

I think the front springs are a common diameter on American cars and circle track cars. I think there might be more out there if we know what we want. The benefit of running the stock spring diameter would be the ability to fit hydraulic bump stops in place of the stock rubber.

I haven't looked into the rears much.

Shocks: Yeah, take some measurements and see what you think you can fit/retrofit in there. I'd have to dig for #s for valving but whatever we were running or any of us ran at one point may not be ideal if we're messing with spring rates, bump stops, etc. anyway. I started looking at the suspension calculator you posted but quickly found out that I had to take a bunch of measurements and didn't have time to do so. It will be interesting to get that populated with the right measurements and see how close/far the recommendations are compared to what people run on 99/900s....

Remote reservoir shocks would really help with the overheating issues we had with the stock-sized Bilsteins that we've been running.

For the one time I did NEFR I got a set of Eibach springs and ran regular Bilstein HD's. It could be a bit bouncy at times in the rough stuff, but in general it felt/drove well.

Fronts were 1300.500.0250 and the rears were 1200.300.0300S (Length.Diameter.Rate)

The only modification was to make a new lower spring perch for the fronts. I copied the basic design of the OE ones out of bent/welded plate. The first set I cut from 3/16" steel and then welded them incorrectly and they didnt fit the springs. Second set (in a last minute rush) were from 12 gauge and slowly bent throughout the rally. Probably would have all worked fine with the 3/16"

Another option to look at would be to use the foam type bumpstops on the shock or spring slider.

I think Luke originally ran SPG springs front and rear. MSS aluminum spacers in the front and the SAS poly spacers in the rear. It worked well for everything except for big jumps where it often bottomed out.

What brand is the coil spring eliminator you got? I'm finding allll sorts of stuff, but not one that looks like yours.
https://www.summitracing.com/parts/aaf-all64100