Well, as of yesterday I have a set of d7 fronts and d4 rears sat waiting to go on...
My spreadsheet has seen a fair bit of work lately, but I've unshared it because a) it's a work in progress, and still has a fair bit of guesswork in it, and b) I've put a lot of time into it, and not sure I'm ready to let that go just yet...
Anyhow, I'm in the process of bringing bump stops into the model, to get a fuller picture of the stock setup and some sort of estimation for bump stop tuning... I won't install my new spring until I know what bump stops I'll pair them with.
I'm not 100% that I'll use the front d7 springs, partly because of their ride height, and partly because I don't think they're as stiff as I want (my 330d is pretty much the same front weight as a 335i, for reference).
My solution, most likely, will be BMW performance springs. They're around 190lb/in rate (compared with my current 120, and 150ish for the d7) - that should give me around 1.5hz nat freq ignoring bump stops, which will match the rear nicely. They should drop the front only about 0.5" lower than m sport, but I'll probably negate much of that by installing a 10mm thick camber plate to get me to around -1.8 - 2.0deg camber. I don't know why I didn't notice it before, but it was definitely a little lightbulb moment when I realised that my spreadsheet was pointing me directly at the BMW perf spring rates.
I've discounted eibach prokit and h&r springs because they seem to drop the front further than is useful, and have very similar rates to the d7 springs. I want to retain near m-sport ride height in order to keep a useful amount of bump travel (it's only about 50mm when you're in the car, at m-sport height!). I may even use e30 perches to increase the front travel.
I'll keep the rear d4, because they're very similar in rate to my current f3, but drop the rear to around m-sport ride height. When I install them, I may beef up the rear shock top mount a bit too (reduce the length of the sleeve, so the foam parts are compressed a bit further initially).
I'd like to get into the shocks a bit more, but the barrier there is dyno printouts...not much around that I can see, and without that I'm flying blind. Also, the maths for calculating desirable damping have one particular step which is a bit much for my little brain...for now at least. I think that if I eventually just have to choose a new shock without calculation I'll just go for yellows. But it would be nice if there was a similar shock with shortened bodies somewhere...?
That's awesome that you're loving your new setup! Do you think you'll lower the front, since you didn't raise the rear? Yeah, the rear top mounts are tapered - you could even just wrap them with electrical tape or similar to fill the gap from installing spacers there...it doesn't need much, and even of it was loose, the fact that it will always have spring pressure on it means it would never come to any harm. I totally agree with your decision to not use the spacers though. When you say your car is now underpowered, you mean you brake too much into turns, right?
