Hey John
I DM'ed you my number. We can talk about bit tomorrow, but I agree with
@Easter Bunny let's keep the nerd talk here on the forum, in case it helps anyone else in the future.
I apologize, I read the first post, and forgot that you were running swift springs already. So forgive my rambling on that.
Spring calculators help. I keep rereading that you want to do occassional track, but still keep the car street able? Some of the spring rates you are talking about kind of push that line. Spring rate ride is definitely subjective to the driver, as far as whats tolerable on the street. You are also wanting to use your KW's. I wouldn't go any higher than 600lbs, just because of the limitation of the KW dampers. The v3's may not be able to handle much more spring. IF you really want to start that high, I would suggest using different dampers.
If you are going for a balanced ride, like flat ride, you will need more spring in the front due to the car being heavier in the front. If you want more oversteer, yes you can overspring the rear, but it may make the car feel a little unbalanced and over sprung, depending on the delta between front and rear spring rates with relationship to the cars corner weight.
You haven't mentioned anything about bushings. I dont think?! You are leaving a LOT on the table, by riding on stock bushings. With the MS3, the front control arms have a LOT of slop in them. Going into high spring rates will make that slop even more pronounced. The car will not handle how you want it. So please consider upgrading some of your bushings as well.
There were several suspension parts that are swapable between the MS3 and the focus ST. A few years ago I was looking at some Ohlins coilovers from Vorshlag, but I ended up just getting caster/camber plates from them instead. My point is, you might be able to cross reference some parts like that as well.
My rear spring perches are e30 or e36 perches from Ground Control. It was the result of many measurements and emails with the GC owner. The perches were off the shelf, but the upper plate they gave me to secure the spring to the subframe, was from some other coilover kit. The set up kind of limits the spring height adjustability range, but I wanted it that way because at the time I wanted to be able to swap the 2.5" springs between front and back. I will need to dig around for those part numbers, no guarantee that I have them.
About the 2.5" ID springs, I had no problem putting them on the front coilovers. IIRC there is very little slop. I dont know about running 60mm springs. You would need to measure the adjustable collar and whatever tophat you are using. I dont remember those measurements, I'm getting old.
Lastly, you mentioned that your sedan is a skyactiv? If so, make sure to maintain all your panels and wheel wells. The Skyactiv has a LOT of aero built into it. Kind of an upper hand on the Skyactiv to the MS3. They left a lot of aero on the table with the MS3 front end. At least on our platform. I can assume Mazda brought that same knowledge into the next platform as well. It WILL make a difference when you hit 36mph or higher on stability.
