e46 M3 suspension setup, or how to not downgrade your car with suspension mods

[Obioban]

Just purely out of curiosity, why full soft up front? Because of the low spring rate?

Yes. A softer spring rate needs less damping to control it.

And too much is a bad situation— the car jacks down (over repeated bumps the spring gets more compressed as the shock is too stiff to let it expand in time to hit the next bump), so you end up driving on the bump stops.

[r4dr]

You should have the fronts on full soft and rears somewhere in the middle of their range, probably. Full soft up front for sure.

maybe more in the rear— 700 is the stiffest spring tck says your can use with their shocks, so it might need to be on the stiffer side to control it.

Just purely out of curiosity, why full soft up front? Because of the low spring rate?

[Obioban]

You should have the fronts on full soft and rears somewhere in the middle of their range, probably. Full soft up front for sure.

maybe more in the rear— 700 is the stiffest spring tck says your can use with their shocks, so it might need to be on the stiffer side to control it.

[duracellttu]

That looks pretty bang on perfect to me. I'd say start your front sway off on medium, and tweak it to taste from there. Medium should put you at 74%, which is a pretty optimal starting point for "medium". I wouldn't worry at all about a 0.4% FRC variance left/right-- unavoidable.

Just finished this project which included CSL king pins, new springs, TMS monoball RTABs, new wheel bearings all around, and 996 Brembos.

During the first drive, the car felt REALLY bouncy. Seemed to be coming strictly from the rear. I have TCK SA shocks and they are set to 3 clicks from full soft front and rear. Spring rates are 350# FL, 336# FR, 700# RL, 657# RR.

Do I need to adjust the shocks to be more firm? Not sure why it's so bouncy. Any advice is appreciated!

[Redline]

Any suggestions for fixing the issue with bilstein HD and eibach bottoming out on anything larger than a 1” bump? Gotten worse over time and feels like I have 2x4”s for front struts, simple bumps have me bracing for impact at speed lol...

[ChapterM3]

Bump for a terrific thread! Currently weighing my options for Koni sports and Dinan springs - if anyone has had experience with this setup I'd appreciate your input! How is the ride for day to day driveability? Anything else I should know before pulling the trigger? Feel free to PM me to not take up space in this thread. Thank you Obioban for the great post!

[Obioban]

Geez I just bought a set of bc and now I'm thinking about going to stock with a set of springs after this read. I have koni with h and r spring but my ride kills my car. +1 on the info

It's more difficult to correctly set the car up with springs/shocks than it is with coilovers. The only springs that I know function properly are Eibachs and Dinans (vogtlands may as well-- I don't know anything about them). Nothing you can do is going to make the H&Rs work well.

[Tbonem3]

H&R springs kinda suck. The rears are fine, but the fronts are awful. Pair some eibachs or dinans or vogtlands with koni or bilsteins.

[Drewrivera]

Geez I just bought a set of bc and now I'm thinking about going to stock with a set of springs after this read. I have koni with h and r spring but my ride kills my car. +1 on the info

[Tones]

It’s the front “knuckle” that connections your strut to the front wishbone and tie rod. Your caliper mounts to it and the wheel bearing presses into it.

Ah okay. I don't think i've ever heard kingpin before but have heard knuckle.

[duracellttu]

Okay what is a kingpin.

It’s the front “knuckle” that connections your strut to the front wishbone and tie rod. Your caliper mounts to it and the wheel bearing presses into it.

[Tones]

Okay what is a kingpin.

[Obioban]

Looks like my idea worked! Did you have to get longer bolts to accommodate the additional spacers? If so, what size bolts and washers did you end up using?

The stock bolts were long enough that I did not need to swap them out for my set up.

[duracellttu]

Then I noticed the the bracket that mounts the sway could just be spacered off the control arm with some washers. You can go either direction, just by spacering one side, vs the other. So long as your ride heights are reasonably the same left/right, this should be plenty to dial out the preload.

Looks like my idea worked! Did you have to get longer bolts to accommodate the additional spacers? If so, what size bolts and washers did you end up using?

[r4dr]

Ohlins has barrel springs, I know 3DM lists the kit for our cars as 630 lb/in. Perhaps they have other rates as well.