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

[wahsm]

Great write up, to add to this there is a good book called “high-performance handling for street or track”

[Obioban]

Fantastic thread! I know setups can vary wildly depending on other suspension/weight modifications. However, for those of us running a mostly stock setup, it would be great to know some general recommendations (spring rates, dampers, ride height, sway bars, etc) to cut through the complexity.

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

[mcfreid]

Fantastic thread! I know setups can vary wildly depending on other suspension/weight modifications. However, for those of us running a mostly stock setup, it would be great to know some general recommendations (spring rates, dampers, ride height, sway bars, etc) to cut through the complexity.

[Obioban]

Other thread was weirdly glitchy (nobody could see changes I was making to the first post), so I made a new thread, moved all the replies over, and deleted the original. That said, you're all unsubscribed as a result :P

[Obioban]

I know what you’re getting at here but I think bullet point 1 and 4 contradict each other. There is a trade off between stiffness and camber of the outer tire. Another consideration, car with unbalanced front to rear roll stiffness and soft stock sways will have less maximum grip than a car with stiffer aftermarket sways if the car has better matched F&R roll stiffness.
Also, stiffness is not as much of a factor on a smooth road.
I think a good takeaway for everyone is that this is very complicated and easy to get the system out of wack when you start changing things.

Hmm, I worded that poorly. I way trying to convey that the stiffer the springs and/or sways are, the less grip you'll get from a given tire. Completely agreed that a stickier tires on a stiffer setup often results in more grip than a less sticky tire on a softer setup. Let me work on rewording that to be clearer...

[T.J.]

Preface

So, generally...
-the stickier your tires are, the more roll stiffness you need
-the less suspension travel you have, the more stiffness you need
-the higher (stiffer) the frequency is, the less grip you have
-the stiffer the sways, the less grip

I know what you’re getting at here but I think bullet point 1 and 4 contradict each other. There is a trade off between stiffness and camber of the outer tire. Another consideration, car with unbalanced front to rear roll stiffness and soft stock sways will have less maximum grip than a car with stiffer aftermarket sways if the car has better matched F&R roll stiffness.
Also, stiffness is not as much of a factor on a smooth road.
I think a good takeaway for everyone is that this is very complicated and easy to get the system out of wack when you start changing things.

[ViN]

This is very helpful. Thank you, Ian.

[Cubieman]

Nice read, always learning!

[liam821]

Yeah, great info, thanks for posting.

[xpme46m3]

Some really good info in here! Thanks!

[Tbonem3]

Hmm, it's something I've noticed for a long time. Even when watching my own car in videos, it squats down in the rear quite a bit (not under hard accel). Oh well.

As for the edits, I swear I still can't see them. I think the site is acting up maybe.

[Obioban]

Here's a question,

When on the freeway, rolling next to a stock looking M car, especially the newer ones, but even e46 and e9x, the front looks super lifted and the rear very squatty. 14.5"/14 or thereabouts might be stock, while static, but when rolling, it looks more like 15/13 lol. Is it because it's a rear wheel drive car? Should we care about the ride height when static or should we focus on what it is, in motion?

Nothing about being in motion (while not accelerating) should cause the rear to sit lower than it does when the car is stationary. My guess is that you're seeing cars with trunks full of stuff or people in the back seat.

Ride height when static with your typical load when driving hard is what you should target.

[Tbonem3]

Here's a question,

When on the freeway, rolling next to a stock looking M car, especially the newer ones, but even e46 and e9x, the front looks super lifted and the rear very squatty. 14.5"/14 or thereabouts might be stock, while static, but when rolling, it looks more like 15/13 lol. Is it because it's a rear wheel drive car? Should we care about the ride height when static or should we focus on what it is, in motion?

[Obioban]

14.5/14" no?

Depends on options and coupe/vert as well I'd imagine. M3s vary in weight quite a bit.

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Got it, thanks Ian.

Yeah, that's roughly correct. Earlier cars (2001-2003) were a little lower/stiffer than later cars (2004-2006).

There isn't that much variety in stock height, as BMW has a ton of different springs they use depending on how the car is optioned.

[Tbonem3]

14.5/14" no?

Depends on options and coupe/vert as well I'd imagine. M3s vary in weight quite a bit.

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Got it, thanks Ian.