Z4 M Springs on Z4 Non-M

[Spec-Al]

Does anyone know if the springs are interchangeable? I did search but didn't see this, guessing because it either doesn't fit or no one has tried. Obviously the stock Z4 non M shocks won't be valved for the Z4 M springs, but it does seem that the Z4 M springs are taller than Z4 non M w/ M sport suspension. Looking for a setup that isn't lower than Z4 non M w/ M sport with a stiffer spring rate. Most coilovers seem to be set up to drop.

[Spec-Al]

Did a little bit of research this morning. Visually the M/non M springs appear similar. Real OEM shows that the upper and lower rear spring pads are the same part number between M/non M, which leads me to believe they'll physically fit. Front however, while the lower spring perch is the same, the upper is different. The entire top mount of the M is different, but may not be interchangeable because the strut shaft diameters probably are not the same. I guess long story short is, unless someone has had both sets of parts in front of them, difficult to say what fits.

[Yapakanichi]

You'll probably need the offset lollipops, upper spring perches, and springs. The rears would probably work, just the shocks are probably different

[rocky79]

Originally Posted by Spec-Al

Does anyone know if the springs are interchangeable? I did search but didn't see this, guessing because it either doesn't fit or no one has tried. Obviously the stock Z4 non M shocks won't be valved for the Z4 M springs, but it does seem that the Z4 M springs are taller than Z4 non M w/ M sport suspension. Looking for a setup that isn't lower than Z4 non M w/ M sport with a stiffer spring rate. Most coilovers seem to be set up to drop.

Did you find an answer to this?
I am in the same boat looking for a stiffer springs without the agressive lowering.

Thanks

[maupineda]

I think they would fit, but the vehicle will actually sit higher since the engine in M is significantly heavier. Rears are closer in terms of rates, I have never seen the actual rate specs, but I think they would be interchangeable.

[cbpip]

M version front springs will not fit a non M car. M sport springs are totally different fitment than M versions. The tops of the M springs are a bit oval in shape where the hat sits on them. M Sports are round in the fitment to the hat and are not interchangeable. Rears are identical from M to non M.

[rocky79]

I ended up buying used swaybars front and back from a Z4M to control the body roll instead of the stiffer springs.

[GuidoK]

Originally Posted by rocky79

I ended up buying used swaybars front and back from a Z4M to control the body roll instead of the stiffer springs.

Rear Z4m swaybar doesn't fit the non M rear axle...

[rocky79]

Originally Posted by GuidoK

Rear Z4m swaybar doesn't fit the non M rear axle...

Thanks for letting me know.
I just noticed there is a bend on the non-M that is not there on the M sway bar.

What do you recomend for a 22mm drop in replacement sway bar?

[GuidoK]

Originally Posted by rocky79

What do you recomend for a 22mm drop in replacement sway bar?

H&R has a 21mm rear swaybar for the non M Z4 that can be bought seperately:
https://www.turnermotorsport.com/p-1...ay-bar-for-z4/
I think ultra racing also has a seperate rear sway bar, but also 21mm and similar price.
The H&R sway bars are adjustable.

Of course you can also buy a kit with the front included, but front z4m and e46 M3 swaybars also fit the non M z4.
However, maybe in some cases you may need adjustable swaybar end links in the front. The correct way to check this is, when installing such a swaybar (and I guess that goes for every aftermarket swaybar), is to jack up the complete front of the car (so both sides at the same time!), so that both sides of the suspension arms are in full droop (full down) and check that the swaybar doesn't touch the suspension arms. If you have adjustable end links, you usually can find that sweet spot where there's no touching.
Jacking up one side at the time results in that the other side of the swaybar gets tension and that prevents the suspension to go into full droop (droop is the amount of travel the suspension goes down compared to when the car sits on it's wheels)

The H&R swaybar kit uses a 27mm swaybar. I use a stock e46 M3 swaybar (26mm), but I use a KW V3 kit that for the z4 has linear springs that are stiffer than what normal progressive springs are. I think my car is pretty much in balance, and wouldn't want it to be stiffer than it now is (it's not a track car). (I think I only needed adjustable links when I installed my KW set though, but it's been a long time since (more than 10 years))

Obviously if you fit different sway bars you need to swap out the bushings to the according diameter. If you buy an aftermarket kit, they are usually included.

[rocky79]

Originally Posted by GuidoK

H&R has a 21mm rear swaybar for the non M Z4 that can be bought seperately:
https://www.turnermotorsport.com/p-1...ay-bar-for-z4/
I think ultra racing also has a seperate rear sway bar, but also 21mm and similar price.
The H&R sway bars are adjustable.

Of course you can also buy a kit with the front included, but front z4m and e46 M3 swaybars also fit the non M z4.
However, maybe in some cases you may need adjustable swaybar end links in the front. The correct way to check this is, when installing such a swaybar (and I guess that goes for every aftermarket swaybar), is to jack up the complete front of the car (so both sides at the same time!), so that both sides of the suspension arms are in full droop (full down) and check that the swaybar doesn't touch the suspension arms. If you have adjustable end links, you usually can find that sweet spot where there's no touching.
Jacking up one side at the time results in that the other side of the swaybar gets tension and that prevents the suspension to go into full droop (droop is the amount of travel the suspension goes down compared to when the car sits on it's wheels)

The H&R swaybar kit uses a 27mm swaybar. I use a stock e46 M3 swaybar (26mm), but I use a KW V3 kit that for the z4 has linear springs that are stiffer than what normal progressive springs are. I think my car is pretty much in balance, and wouldn't want it to be stiffer than it now is (it's not a track car). (I think I only needed adjustable links when I installed my KW set though, but it's been a long time since (more than 10 years))

Obviously if you fit different sway bars you need to swap out the bushings to the according diameter. If you buy an aftermarket kit, they are usually included.

Thank you for the detailed explanation. I will check out the H&R sway.

The front sway bar that I got came with the stock bushing ( 86kmiles Z4M) The bushing look in great condition. They have the right amount of softness.

I am tempted to install them, don’t want the stiff aftermarket PU bushing.
What do you think?
OEM bushings go for closes to $100 each. very pricy.