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

[tlow98]

Couple disclaimers:
1) you should really run the numbers! It doesn't take that long and it's amazing how quickly small changes DO make your car different. There's a reason BMW used so many different spring combinations, depending on how your car was optioned.
2) I'm going to suggest a flat ride setup, which some people are on board with and some are not. I very intentionally avoided flat ride in the original post, to keep everything uncontroversial. I've been running flat ride for while on all my cars, and am hugely on board with it at this point.

That said, for a very close to stock car, this would likely be pretty stellar:
TCK SAs
300 lbs front springs, 700 lb rear springs
Turner front sway (with turner sealed adjustable end links)
stock rear sway

If street only: e36 strut hats

If also track: Camber plates (I like the turner hybrids) and adjustable rear control arms
-possibly also swap out front sway for GC Race sway (unsealed end links will get noisy over time on GC's) and swap stock rear sway for CSL rear sway

Thanks for this, Obioban. After much research, I believe I'm headed in exactly this direction for my E46 sedan (TCK SAs 300/700, Turner endlinks). I'm not familiar with the E36 strut hats on the E46 platform. Is there a specific reason why you called that out here? Camber advantages?

The car will be a streetcar, on PS4S or similar traction levels, for now. I had a full GC set up in the past; coils 400/500 (IIRC), sways, and plates. It was ok, but it came with the car and had an unknown life. Everything would respond to adjustments but always struck me as a little harsh. Previous to that I had a Koni yellow + stock spring combo that was, well, lovely. This was all on my E46 m3. The sedan is much softer in its stock form. It's a 330i for reference. The balance is really good, but I need real bite and the stock stuff is all worn-out original items. This is meant to be a 'beater' with great dynamics. The springs available for the 330i are lacking and the M3 set up bolts right in. Plus I'm looking for more precision than 'just' Koni yellows.

Also, mega appreciate all that went into this thread. The decades of trial/error and the spreadsheets from FCM. It's really eye-opening and I'm incredibly happy to return to the E46 platform. I moved my E91 on to my sister as she loved it and I fell out of love with it. Sounds like you know that story!

[Obioban]

I want to give Ian and others who have contributed to this thread props for putting this knowledge out there for the rest of us. I keep coming back to this thread. It has helped to plug gaps in my knowledge of suspension setup that have been out there for a long damn time.


Genuinely thankful to this community.

Edit: to remove the unnecessary drivel.

Hey now, these threads can be selfish. I like to write them up when everything is freshly researched so I can refer back to them later, after I've forgotten

[Casa de Mesa]

I want to give Ian and others who have contributed to this thread props for putting this knowledge out there for the rest of us. I keep coming back to this thread. It has helped to plug gaps in my knowledge of suspension setup that have been out there for a long damn time.


Genuinely thankful to this community.

Edit: to remove the unnecessary drivel.

[JustAWhisper]

OptimumG has a 6-part tech tip on springs and dampers, part 1 summarizes ride frequency theory in just 4 pages.

You're also correct, ride frequencies will change with front and rear weight changes. I wouldn't be too worried about overall changes, but if your weight distribution changes significantly then your F/R ride frequency ratio will change accordingly (you'd have to use the FCM spreadsheet to calculate if that difference is enough to be a cause for concern).

Thanks, I'll check it out. I also stumbled across a guide that's laid out in a way that's much easier for me to digest. http://farnorthracing.com/autocross_secrets16.html

[timmo]

Reviving this thread. I'm in the process of procuring my first proper track suspension setup. I've long known most of the off-the-shelf coilover spring setups are garbage, but figuring out spring rates as a novice is quite difficult. I read the original post 4 times and I've played with the spreadsheet some, but it's all still completely greek to me, and this is coming from an engineer.

Does anyone have any good resource recommendations for figuring this stuff out? I own a copy of the Milliken Race Car Vehicle Dynamics book, but I've never been able to get through that, either.

Also, a quick question. I know that a lot of these calculations depend on car weight. But car weight is a bit of a moving target, as theoretically I'll be slowly removing weight over time in order to improve the car. I assume this means that spring rates will need to change at some point? Is there a way to effectively plan for future weight reduction when going through this process?
Thanks.

OptimumG has a 6-part tech tip on springs and dampers, part 1 summarizes ride frequency theory in just 4 pages.

You're also correct, ride frequencies will change with front and rear weight changes. I wouldn't be too worried about overall changes, but if your weight distribution changes significantly then your F/R ride frequency ratio will change accordingly (you'd have to use the FCM spreadsheet to calculate if that difference is enough to be a cause for concern).

[JustAWhisper]

Reviving this thread. I'm in the process of procuring my first proper track suspension setup. I've long known most of the off-the-shelf coilover spring setups are garbage, but figuring out spring rates as a novice is quite difficult. I read the original post 4 times and I've played with the spreadsheet some, but it's all still completely greek to me, and this is coming from an engineer.

Does anyone have any good resource recommendations for figuring this stuff out? I own a copy of the Milliken Race Car Vehicle Dynamics book, but I've never been able to get through that, either.

Also, a quick question. I know that a lot of these calculations depend on car weight. But car weight is a bit of a moving target, as theoretically I'll be slowly removing weight over time in order to improve the car. I assume this means that spring rates will need to change at some point? Is there a way to effectively plan for future weight reduction when going through this process?
Thanks.

[Toby22]

Great thread!

on side note, anyone have any feedback on these AST 2000? Can’t find any reviews on this. $1.3k seems like it competes with kw v1 in price range

[mrgizmo04]

Was the first post hidden?

That seems to be a tapatalk issue. If you open the thread in mobile browser (or assuming on desktop too), you see the first post by Obi, not Tbone.

Sent from my SM-G950U using Tapatalk

[IamFODI]

That was the first thing I thought. But i have plenty of travel before hitting the bump stops.

"Bump stiffness" = compression damping = how much resistance the damper applies on a bump/compression stroke.

T.J. is suggesting that the excessive stiffness in your suspension might be coming from the dampers more than the springs (not that I know enough to agree or disagree).

[maupineda]

It’s probably the bump stiffness of the damper rather than the spring

That was the first thing I thought. But i have plenty of travel before hitting the bump stops.

[T.J.]

Question for those with more experience and knowledge. I have a Z4M, and this car is particularly stiff, in all possible setups, even the OE suspension is overly stiff. I currently have H&R Coils, and the rear is rock hard, so I was thinking about getting TCK 400 rear springs, the front is ok, stiff but not jarring, the rear is particularly bad. Many swear by KW V3 and how it makes it the best of two works, but to be honest, when I see the spring rates, I don't think they will be much better. The good about TCK springs is they are linear, and this may be a good compromise for me. I don't track the car, so I don't care much about extreme flat cornering, but after a sporty drive I can enjoy as much as possible.

I don't know the rates of my setup, could not find anything online. These are the spings I am looking at. https://www.tcklineracing.com/webdoc...Details379.cfm

EDIT: I called H&R and they don't release their spring rates, but the rep did tell me the Coilover kit has the race spring, which are stiffer. so my idea of going to the TCK may work for me.

It’s probably the bump stiffness of the damper rather than the spring

[Chas3n]

Was the first post hidden?

[maupineda]

Question for those with more experience and knowledge. I have a Z4M, and this car is particularly stiff, in all possible setups, even the OE suspension is overly stiff. I currently have H&R Coils, and the rear is rock hard, so I was thinking about getting TCK 400 rear springs, the front is ok, stiff but not jarring, the rear is particularly bad. Many swear by KW V3 and how it makes it the best of two works, but to be honest, when I see the spring rates, I don't think they will be much better. The good about TCK springs is they are linear, and this may be a good compromise for me. I don't track the car, so I don't care much about extreme flat cornering, but after a sporty drive I can enjoy as much as possible.

I don't know the rates of my setup, could not find anything online. These are the spings I am looking at. https://www.tcklineracing.com/webdoc...Details379.cfm

EDIT: I called H&R and they don't release their spring rates, but the rep did tell me the Coilover kit has the race spring, which are stiffer. so my idea of going to the TCK may work for me.

[timmo]

That's so bizarre, do you know if he bought it from a 3rd party dealer? Maybe the dealer put together a kit for him.

Yeah it's really odd - no, it was purchased directly from GC, the build sheet shows that it was shipped directly from GC to him. GC's view is that the kit was definitely pieced together, which obviously makes sense from their POV.

It's kind of crappy but aside from dynoing the shock, I guess I'll have to bump up the rear spring rate, maximize the stiffness on the adjusters, then see if it feels underdamped, to see if the rear shock was revalved or not

[r4dr]

That's so bizarre, do you know if he bought it from a 3rd party dealer? Maybe the dealer put together a kit for him.