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

[Tbonem3]

Bilstein (H&R) and KW have progressive springs. I'm not sure you can do "flat ride" with progressive springs. If you're looking to convert to linear, then what would it matter what billy's and kw's rates are? You can reasonably expect those dampers to handle up to about what other mid-tier dampers can, around 600-700 is my guess.

[r4dr]

Yup Ive seen those. Problem is, I have a camber plate for the stock spring diameter. So I need to change out that and the springs

What camber plates do you have? Getting a perch for coilover springs might not be too hard or $$ depending on the brand.

I'm in a similar boat with KW V2s on from the previous owner, but with no camber plates. Once I put that HPA kit together, I'm not sure it's worth the difference of just buying a set of TCK SAs (or SA fronts/DA rears) and selling the V2s.

[duracellttu]

I'm running 350 front left, 325 front right, 700 rear left, 628 rear right (which results in the same frequencies left/right with just me in the car).

When using the flat ride spreadsheet, matching the bounce frequencies left and right cause the left and right FRC to mis-match. I'm assuming it's more important to match the bounce frequencies?


Just today I go my corner weights measured with just me in the car. 50% cross weight looks like FL: 912# FR: 887# RL: 897# RR: 863#

I'm trying to find out what spring rates are best to go with for flat ride. Any advice?

My setup is TCK SA, TMS front sway, stock rear sway. Using the flat ride calculator I'm proposing FL: 350# FR: 336# RL: 700# RR: 672# (mix between hyperco and swift springs to achieve those rates)

[Obioban]

When using the flat ride spreadsheet, matching the bounce frequencies left and right cause the left and right FRC to mis-match. I'm assuming it's more important to match the bounce frequencies?


Just today I go my corner weights measured with just me in the car. 50% cross weight looks like FL: 912# FR: 887# RL: 897# RR: 863#

I'm trying to find out what spring rates are best to go with for flat ride. Any advice?

My setup is TCK SA, TMS front sway, stock rear sway. Using the flat ride calculator I'm proposing FL: 350# FR: 336# RL: 700# RR: 672# (mix between hyperco and swift springs to achieve those rates)

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.

[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.

I've been thinking about how to approach this methodically for a while, so thanks for all of the advice! Your spreadsheet screen shots are exactly what I show in my version.

Is it true that you have to use linear rear springs to achieve "flat ride"? I thought I saw a comment about that somewhere.

[Obioban]

I've been thinking about how to approach this methodically for a while, so thanks for all of the advice! Your spreadsheet screen shots are exactly what I show in my version.

Is it true that you have to use linear rear springs to achieve "flat ride"? I thought I saw a comment about that somewhere.

Not true-- it'll just mean you have a variable flat ride ratio :P

What rear springs are you thinking about running? Not a ton of progressive springs with listed rates I know of.

[duracellttu]

Not true-- it'll just mean you have a variable flat ride ratio :P

What rear springs are you thinking about running? Not a ton of progressive springs with listed rates I know of.

Ahh gotcha. I'm not too familiar with the progressive spring options outside of TCK. I just wanted to know the implications of using progressive vs linear rear springs. Looks like progressive springs have more travel, but induce variable flat ride and linear have less travel but static flat ride.

For the TCK SA setup I'm running, my plan was to go with 60mm, 7 inch length front springs from Hyperco for 350# and Swift for 336# (6 kgf/mm, imperial).

I'm having trouble finding a rear set that have the same ID size. Since I am running the RE weighted jacks in the rear run I need to use either 60mm or 2.25" ID. I think 5 inch is the correct spring length from my research.

Hyperco has a 2.25 inch, 5 inch length (no 60mm ID available in 5 inch) 700# and from Swift 60mm ID, 5 inch for 672# (12 kgf/mm, imperial).

Should I be concerned with mixing 2.25" and 60mm? Do you know where I can get a 2.25" ID, 5 inch 672# spring? Or am I stuck mixing since the spring rates are mixed units?

[Obioban]

The TCK rear springs aren’t progressive. There no issue mixing springs sizes so long as they all fit correctly. I’d stick to a tck style barrel spring if you can.

[duracellttu]

The TCK rear springs aren’t progressive. There no issue mixing springs sizes so long as they all fit correctly. I’d stick to a tck style barrel spring if you can.

Know of any barrel style springs that are made with imperial spring rates?

Update: Looks like BW sells Eibach 2.25" ID, 5" length springs in 25# increments, so I can get a 675#. These appear to be straight type, not barrel.

[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.

[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?

[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.

[Tones]

Okay what is a kingpin.

[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]

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.