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

[Bry5on]

Maybe I missed it but how low can you go in the rear before you start compromising suspension geometry?

I’m 13.5 left and 13.75 right fender to center of wheel in the front but 12.75 left and 13 right in the rear measured with no driver. I’m right at 50/50 crossweights with the driver. My seating position is far enough back so my fat arse distributes more weight to the rear. So I’m sure the rear heights with me in it are lower.

Im really happy with the car’s performance as is. I’ve lucked out and been able to balance the car out with aero. I’m wondering if I can get a little more mechanical grip in the rear so I can take off the gurney flap which adds a ton of drag with my Amazon.com wing that I bought with Hilton points 🤣

Very little change from lowering the rear, camber and track changes are basically linear, and the roll center barely moves. You’re just fine

edit: you lose anti-squat performance from lowering the rear, still probably not a huge deal but you’ll be giving up a little rear grip on acceleration as you’ll increase negative camber just when you want positive (near zero) camber for traction.

[tlow98]

I have the B12 Pro kit on my Z4M with 19" tires and the drop is lovely but hitting the smallest pothole makes it sound like you slammed into a brick wall. Even the oem suspension with 18" tires sounded like that. Just a very stiff chassis. Everytime I hit a pothole I feel like I bent a wheel. On smooth roads its a comfortable ride otherwise and the thing handles amazin !

They Z cars are interesting. They lacks the travel of the sedans and coupes from which they’re mostly built on. So, lowering them puts you in situation where you go from very little travel to almost nothing.

[01SG]

They Z cars are interesting. They lacks the travel of the sedans and coupes from which they’re mostly built on. So, lowering them puts you in situation where you go from very little travel to almost nothing.

Are you sure about this? I do not see why the Z would not have the same exact travel as the M3. It is basically the e36 m3 front suspension mated to the e46 m3 rear suspension. Any of these cars are not exactly soft stock. Putting 19s on a Z would be bad for the ride on its own, lowering it on top of that would certainly explain any ride degradation.

As for the cat asking about B4/Dinan and whatever...I say keep stock springs no matter what shock. I have now gone from stock to lowering springs and back to stock on both my Ms and could not be happier.

[tlow98]

Are you sure about this? I do not see why the Z would not have the same exact travel as the M3. It is basically the e36 m3 front suspension mated to the e46 m3 rear suspension. Any of these cars are not exactly soft stock. Putting 19s on a Z would be bad for the ride on its own, lowering it on top of that would certainly explain any ride degradation.

As for the cat asking about B4/Dinan and whatever...I say keep stock springs no matter what shock. I have now gone from stock to lowering springs and back to stock on both my Ms and could not be happier.

I'm quoting Jason Cammissa when I say that. My understanding is the springs are shorter (and the bump stops are certainly shorter). Shocks are shorter and have different bodies, as well. I love the cars, but straying from stock and shortening the already shortened suspension is a tough pill to swallow. They are generally a bit lighter which helps, I think. FWIW, I have not compared each component in my hand with the Z4 gen, tho, I have with the E36/7 gen. They are most certainly lacking travel compared to the E36.

[01SG]

Interesting. I figured the harsher ride simply came from the stiffer chassis and sitting over the rear wheels.

[maupineda]

Z4M shocks have 5in of travel. I compared the stock v h and r and travel wise they were the same. So lowering the car just ate travel. I think e46 have also 5in of total strut travel.

[Bry5on]

Z4M shocks have 5in of travel. I compared the stock v h and r and travel wise they were the same. So lowering the car just ate travel. I think e46 have also 5in of total strut travel.

Stock e46 M3 rear has 4.5” droop, 5” bump, 1.4” until contacting the bump stop

[dukeofchen]

Stock e46 M3 rear has 4.5” droop, 5” bump, 1.4” until contacting the bump sto

Any chance you know what these stock numbers are for the front?

[Bry5on]

Any chance you know what these stock numbers are for the front?

Sadly I do not, it’s a little harder to measure this directly. I’m interested if someone does have them!

[maupineda]

Stock e46 M3 rear has 4.5” droop, 5” bump, 1.4” until contacting the bump stop

I was referring to the fronts. Then i noted i used the wrong terminology. I meant struts

for the rear, the B8 were a good 25mm shorter. So droop was the same shorter

i will find some photos a they can be of use to some

[cobra]

I increasingly feel like the more I know about suspension, the less I know about suspension.

... and that deviating from stock as little as possible (but as much as necessary) is the best strategy-- especially in ride height and geometry.

For me the hardest part as I learn more is letting go of things I thought were true. And then realizing I was wrong yet again just weeks/months later! Also, understanding there is no "right" answer, and instead multiple solutions. And what works for one person might not work for another.




Regarding the lowering discussion, there is just hardly any room to lower the E46 if you want to maintain civility and performance. I highly recommend not lowering it more than a teeny tiny bit unless you run shorter shocks to maintain some travel before hitting the bump stops. And then you have to be careful about the tire hitting the fenders or fender liners. Not to mention all the geometry stuff that gets messed up when you start lowering.

Then again some people just want it to look cool and don't care how it rides. To each their own!

[Feffman]

If you go bigger sway bars, may I suggest you reinforce the sway bar mounting area with Bimmerworld's reinforcement kit (https://www.bimmerworld.com/BimmerWo...i-330i-M3.html). Just a thought after last weekend.

Feff

[cobra]

If you go bigger sway bars, may I suggest you reinforce the sway bar mounting area with Bimmerworld's reinforcement kit (https://www.bimmerworld.com/BimmerWo...i-330i-M3.html). Just a thought after last weekend.

Feff

Yikes!

[Feffman]

Yikes!

This is a common know failure yours truly did not know about. The learning curve never ends. 🤑

Feff

[IamFODI]

This is a common know failure yours truly did not know about. The learning curve never ends. 🤑

Feff

Obioban knows nothing about this

Nothing at all