[FaRKle!]

In this post I take a look at the various BMW suspensions (OE and M-Performance) to get a bit of insight on the original design by looking at ride frequencies.

Common Perceptions

BMW suspensions are colloquially referred to as "base," "M-Sport," "xDrive," and "M-Performance." Among these there are common perceptions that sDrive vehicles can have base, M-Sport, and M-Performance suspensions available, and xDrive vehicles only really have the base suspension, even if the EDC/Adaptive-M dampers are selected. We'll find out this isn't necessarily true.


Methods

To find the ride frequencies I looked up the official vehicle weights and weight distributions to get the F/R corner weights. Then I used RealOEM (and other sources to verify if it didn't seem right) to find the weight of unsprung parts and subtracted that from the corner weights to get the "sprung corner weights." Lastly, for the springs I used the BMW ETK system to look up the various spring PNs per model/config and some proprietary information to calculate the frequencies.


Ride Frequency Findings

One thing that surprised me after doing all the calculations across the US F30/31/32/34/36 models was that it really looks like BMW has target frequencies for the front suspension across their various suspension levels. For example, on base suspensions the target appears to be ~1.2Hz, for M-Sport/M-Adaptive it's ~1.33Hz, and for M-Performance it's ~1.55Hz.

For the rear ride frequencies BMW tends to make them 8-12% higher than the front to achieve flat ride/fast settling. That said, there are some exceptions to this. For some reason on all F32s, the front/rear frequency ratio is less (2-8%), and the F32 M-Perf suspensions can even get into a pitch regime where the front and rear ride frequencies are about equal. My guess is that this is to make the F32 feel sportier, without actually giving it more capability.

For comparison, when I did the same activity on F8x vehicles, the F80/82 base suspension front was about ~1.35Hz, competition pack ~1.45Hz, and the rear ride frequencies were 15-20% higher. The M2 suspensions have even higher front frequencies around the 1.5-1.55Hz range, which is probably why people say those cars feel more responsive than F80/82's.

M-Perf suspensions bring the front and rear ride frequencies close to that of the M2s, so vehicles with those should feel similarly responsive.


Model/Chassis Trends

Before, I spoke of the perception of "base" and "M-Sport" suspensions, but the reality is that some models' "base" is more like others' "M-Sport." For example, the F30 sDrive cars have the different base and M-Sport suspensions we're all used to, however F32 and F36 base and M-sport package cars have the same springs. This explains why people say the F32/36 base handles better than F30 base, because they already come with M-Sport springs.

Additionally, for xDrive vehicles the Adaptive-M suspensions come with stiffer springs than the base suspensions, which makes their ride frequencies equal to sDrive M-Sport. This differentiates the xDrive base, and Adaptive-M suspensions more than previously commonly thought!

Another thing I've seen are that 4cyl xDrive front springs are the same as 6cyl sDrive front springs in many cases. This means that 4cyl xDrive cars can get most of the way to an M-Performance suspension by ordering the same front/rear springs as the 6cyl sDrive version, the M-Performance rear shocks (which fit both sDrive and xDrive), and means the only missing piece are the M-Performance front struts. An aftermarket front strut where the mfg overdamps it (for the OE springs) to make it feel sporty can probably get you close to the M-Perf front strut, or you can have a custom shock tuner do one for you. This commonality between 4cyl xDrive and 6cyl sDrive fronts should also be helpful information for people looking at aftermarket springs and what those mfgs recommend vs how OE is set up.

Additionally, on heavier rear-end cars (like F31/F34, or F30 330e) aftermarket rear springs might not be any stiffer than OE, and actually softer! That could cause you to poorly tune your ride frequencies and end up in a pitch regime if the front spring rate is increase and the rear is decreased. This is one of the reasons I think that companies who recommend the same coilover for F31/33/34 as F30 are doing you a disservice. They simply haven't done the calculations and seen how their product really works on those platforms.


Please don't PM me about springs for your car, 1) so we can keep the info public to help others and 2) I'm not your personal consultant, unless you're buying one of the spring sets I have for sale or want to pay me a consulting fee, haha.

[andino]

I'll add my anecdotal experience to this using a KW V1s and Bilstein B14s on my car. These are all in the context of xdrive for F31 since that's what I drive.

KW V1s have a specific kit for f31/f34 which use. I found the ride quality of the V1s quite nice. The day to day commuting with them is comfortable and there's not much see-sawing. Where I didn't like them was when I was deep into a corner and they began to feel a bit under dampened. This was the primary reason why I sold them and switched over to Bilsteins.

I currently run Bilstein B14s. This setup makes the car feel much more lively but at great expense to ride comfort. Bilstein uses a single part number across all f3x cars only differentiating by xdrive or sdrive. This means that the rear spring is under sprung (as Farkie mentions in his post) and my car has a pretty poor ride when the bumps come continuously. Basically, it'll feel like I'm see-sawing quite a bit over my KW that I'd replaced. The benefit (and why I still run them now) is that the b14s feel much more planted in turns and under spirited driving conditions. This is likely to them being much more dampened compared to the KWs.

I only know the ending for the rates for the the bilsteins so its hard to say how they compare to the KWs. At some point, I'll be handing them over to a suspension tuner to get them dialed in for my car. I did find that running an eibach spring equivalent to almost the f80 ZCP up front with an adaptive damper vastly improved my ride so I may end up changing out my spring setup for different ones to improve the road going characteristics. It really depends how the car feels on track after I get some time out there.

[Astute]

First off, I thoroughly enjoy reading through these suspension posts, Farkle. Thank you for putting all this information together in different posts. Subscribed to all of them.

Secondly, I'm currently looking at suspension options for my 340i RWD with track handling - so adaptive suspension and want to achieve a very mild drop, have more responsiveness, and less body roll. I'm debating between these choices right now - I'm also thinking of doing the F8x LCAs

1) M performance suspension
2) Dinan springs, bump stops, shockware
3) F8x ZCP springs (bump stops?)

I wondered which option would help me achieve my goals while not breaking the bank. I'd also like to fit the M performance front lip eventually too, so going too low wouldn't be conducive to that. Any help or thoughts are definitely appreciated!

[FaRKle!]

Originally Posted by Astute

First off, I thoroughly enjoy reading through these suspension posts, Farkle. Thank you for putting all this information together in different posts. Subscribed to all of them.

Secondly, I'm currently looking at suspension options for my 340i RWD with track handling - so adaptive suspension and want to achieve a very mild drop, have more responsiveness, and less body roll. I'm debating between these choices right now - I'm also thinking of doing the F8x LCAs

1) M performance suspension
2) Dinan springs, bump stops, shockware
3) F8x ZCP springs (bump stops?)

I wondered which option would help me achieve my goals while not breaking the bank. I'd also like to fit the M performance front lip eventually too, so going too low wouldn't be conducive to that. Any help or thoughts are definitely appreciated!

I would say that #2 and #3 are probably fairly similar and comparable, but #1 will be a good bit different from those two, and more expensive (probably by double). It will have a significantly higher ride frequency in the front and different damping characteristics. I haven't seen a shock dyno of the M-Perf dampers unfortunately. The M-perf suspension should feel the most responsive.

If you can get the spring rates for the Dinan springs I can give you a better idea of how they'd compare with F80 ZCP springs. I don't believe shockware was co-developed/optimized specifically for Dinan springs and bump stops, despite what marketing might imply. If it was, they'd probably have different shockware profiles for different F3x cars, but it doesn't look that way (same PN across different models).

The F8x ZCP spring kit I have for sale will drop the front and rear about 0.3". The final spring rate on the ZCP rear spring will give the same rear ride freq as the M-Perf kit.

If you want to do incremental upgrades I'd try either the Dinan or F8x springs with F8x bump stops, and then if you want more from there get shockware. If you want to change things up more radically, then just go for the M-Perf suspension.

[Astute]

Originally Posted by FaRKle!

I would say that #2 and #3 are probably fairly similar and comparable, but #1 will be a good bit different from those two, and more expensive (probably by double). It will have a significantly higher ride frequency in the front and different damping characteristics. I haven't seen a shock dyno of the M-Perf dampers unfortunately. The M-perf suspension should feel the most responsive.

If you can get the spring rates for the Dinan springs I can give you a better idea of how they'd compare with F80 ZCP springs. I don't believe shockware was co-developed/optimized specifically for Dinan springs and bump stops, despite what marketing might imply. If it was, they'd probably have different shockware profiles for different F3x cars, but it doesn't look that way (same PN across different models).

The F8x ZCP spring kit I have for sale will drop the front and rear about 0.3". The final spring rate on the ZCP rear spring will give the same rear ride freq as the M-Perf kit.

If you want to do incremental upgrades I'd try either the Dinan or F8x springs with F8x bump stops, and then if you want more from there get shockware. If you want to change things up more radically, then just go for the M-Perf suspension.

Only thing I'm seeing on multiple sites is that the Dinan spring rates are an increase of 25% in stiffness in front and 34% in the rear. Which (forgive my math, if it's off) would potentially work out to ~1.66Hz and ~1.78Hz, respectively? (based on your estimate of Msport spring rate at 1.33Hz)

Based on your response, the F8x ZCP springs seem like they'd fit my needs pretty well. So with ZCP springs, I'm guessing one would need the ZCP bump stops as well or are they universal?

[FaRKle!]

Originally Posted by Astute

Only thing I'm seeing on multiple sites is that the Dinan spring rates are an increase of 25% in stiffness in front and 34% in the rear. Which (forgive my math, if it's off) would potentially work out to ~1.66Hz and ~1.78Hz, respectively? (based on your estimate of Msport spring rate at 1.33Hz)

Based on your response, the F8x ZCP springs seem like they'd fit my needs pretty well. So with ZCP springs, I'm guessing one would need the ZCP bump stops as well or are they universal?

The problem is you don't know what the reference is for Dinan's claims. 25/34% from the base suspension, or M-Sport suspension springs? If it's from base suspension, then the rates end up being a bit softer than F80/82 base suspension. If it's from M-Sport/EDC springs, then the rates end up being about the same as F80/82 ZCP.

I commend you for trying to do some calculations to see where things might end up for you. Unfortunately frequency doesn't scale linearly with spring rates. The equation is square root(spring rate N/m divided by mass kg) divided by 2pi.

For the bump stops I'd recommend going with F8x ones (you can get the PNs from my other thread).

If you'd like to buy a set of ZCP springs I can put together the Eibach front spring and F8x ZCP rear spring from my for sale post to make one. You should end up with a front ride freq of about 1.47Hz front and 1.70Hz rear, same as an M3/4 ZCP.

[Astute]

Sent you a pm regarding your set that you have for sale. An attempt was made to math. Good thing I’m a psychologist and not an engineer.

[McLaren720s]

Originally Posted by andino

I'll add my anecdotal experience to this using a KW V1s and Bilstein B14s on my car. These are all in the context of xdrive for F31 since that's what I drive.

KW V1s have a specific kit for f31/f34 which use. I found the ride quality of the V1s quite nice. The day to day commuting with them is comfortable and there's not much see-sawing. Where I didn't like them was when I was deep into a corner and they began to feel a bit under dampened. This was the primary reason why I sold them and switched over to Bilsteins.

I currently run Bilstein B14s. This setup makes the car feel much more lively but at great expense to ride comfort. Bilstein uses a single part number across all f3x cars only differentiating by xdrive or sdrive. This means that the rear spring is under sprung (as Farkie mentions in his post) and my car has a pretty poor ride when the bumps come continuously. Basically, it'll feel like I'm see-sawing quite a bit over my KW that I'd replaced. The benefit (and why I still run them now) is that the b14s feel much more planted in turns and under spirited driving conditions. This is likely to them being much more dampened compared to the KWs.

I only know the ending for the rates for the the bilsteins so its hard to say how they compare to the KWs. At some point, I'll be handing them over to a suspension tuner to get them dialed in for my car. I did find that running an eibach spring equivalent to almost the f80 ZCP up front with an adaptive damper vastly improved my ride so I may end up changing out my spring setup for different ones to improve the road going characteristics. It really depends how the car feels on track after I get some time out there.

Thanks for the info! I’m getting the B14 installed next month and I can hardly wait to see the change. I hate the stock XDrive suspension. It’s tall and floaty so actually looking forward to a stiffer ride.

Is it easy to adjust the ride height or do you need a shop to do it?

[JaredG_F30]

I wonder if the see-sawing you are experiencing could have been resolved by the B16 with adjustable damping and ride height. Also, I'm on the F30 chassis and wonder if my experience would be the same as your with the B14.

Originally Posted by andino

I'll add my anecdotal experience to this using a KW V1s and Bilstein B14s on my car. These are all in the context of xdrive for F31 since that's what I drive.

KW V1s have a specific kit for f31/f34 which use. I found the ride quality of the V1s quite nice. The day to day commuting with them is comfortable and there's not much see-sawing. Where I didn't like them was when I was deep into a corner and they began to feel a bit under dampened. This was the primary reason why I sold them and switched over to Bilsteins.

I currently run Bilstein B14s. This setup makes the car feel much more lively but at great expense to ride comfort. Bilstein uses a single part number across all f3x cars only differentiating by xdrive or sdrive. This means that the rear spring is under sprung (as Farkie mentions in his post) and my car has a pretty poor ride when the bumps come continuously. Basically, it'll feel like I'm see-sawing quite a bit over my KW that I'd replaced. The benefit (and why I still run them now) is that the b14s feel much more planted in turns and under spirited driving conditions. This is likely to them being much more dampened compared to the KWs.

I only know the ending for the rates for the the bilsteins so its hard to say how they compare to the KWs. At some point, I'll be handing them over to a suspension tuner to get them dialed in for my car. I did find that running an eibach spring equivalent to almost the f80 ZCP up front with an adaptive damper vastly improved my ride so I may end up changing out my spring setup for different ones to improve the road going characteristics. It really depends how the car feels on track after I get some time out there.

[rcaso26]

Hi I currently have KW street comfort coilovers installed on my 2015 328i xdrive. My ride height is lowered, but not slammed or anything. I find the ride very harsh and the suspension bottoms out over large bumps in the road. I still have runflat tires which I suspect are contributing to the problem, but I just wanted to remove the monster truck wheel gap without ruining the ride quality. At this point, it's embarrassing to have other people in the car since the ride quality is so bad. Is there an OEM option or simple option to slightly reduce the ride height while maintaining normal driving comfort? Thanks in advance!

[FaRKle!]

Originally Posted by JaredG_F30

I wonder if the see-sawing you are experiencing could have been resolved by the B16 with adjustable damping and ride height. Also, I'm on the F30 chassis and wonder if my experience would be the same as your with the B14.

It can be addressed that way, but the tradeoff is you're now overdamping and causing the ride to be more harsh overall.

Originally Posted by rcaso26

Hi I currently have KW street comfort coilovers installed on my 2015 328i xdrive. My ride height is lowered, but not slammed or anything. I find the ride very harsh and the suspension bottoms out over large bumps in the road. I still have runflat tires which I suspect are contributing to the problem, but I just wanted to remove the monster truck wheel gap without ruining the ride quality. At this point, it's embarrassing to have other people in the car since the ride quality is so bad. Is there an OEM option or simple option to slightly reduce the ride height while maintaining normal driving comfort? Thanks in advance!

Yes there are OE options from other models that can lower your car and maintain the same spring rate as you originally had. Do you want to maintain the original spring rate, or go stiffer some?

[rcaso26]

Originally Posted by FaRKle!

It can be addressed that way, but the tradeoff is you're now overdamping and causing the ride to be more harsh overall.




Yes there are OE options from other models that can lower your car and maintain the same spring rate as you originally had. Do you want to maintain the original spring rate, or go stiffer some?

Thanks for the reply. Preferably the original spring rate. I just want the car lowered moderately. I live on long island with horrible roads and while the KWs are great on smooth pavement, the stiffer springs are tough on these roads.

[FaRKle!]

Originally Posted by rcaso26

Thanks for the reply. Preferably the original spring rate. I just want the car lowered moderately. I live on long island with horrible roads and while the KWs are great on smooth pavement, the stiffer springs are tough on these roads.

BMW ETK says your car should've come with 31336851718 in the front and 33536851727 in the rear. If you have your original rear springs you can verify this by looking at the bar code sticker on the springs. The fronts should have "DH" and the rear should have "EF" on them.

If that's true, then you can try front spring 31336851921 and rear springs 33536855543 or 33536855544, which are slightly stiffer than your OE springs. The bar codes are "FG," "GO," and "GP." I estimate these will lower by a bit less than an 3/4".

[rcaso26]

You're the man! I'll check tonight.

[gippy]

if i don't release pressure on the brakes and come to a halt, the car will rock on its suspension briefly after its stopped, like some kind of old cadillac.
my previous FK2 Type R never did that. It really was race car like. i miss it in that regard....

the suspension has been truly one of the biggest dissappointments of the car....(M sport passive)

what's the cheapest way i can stop the awful diving and pitch especially under braking.

[Jvac]

I've read that the m performance suspension kit is not compatible with the adaptive suspension. Getbmwparts also says this in their sale post in the classifieds section. So if you did get it installed you'd have to get the adaptive function coded out. I was interested in the kit myself but the lack of information in that regard turned me away. If anybody has installed the performance suspension on a car with adaptive dampers, I'd love to hear their experiences. Opinions on the kit are otherwise very positive

Originally Posted by Astute

First off, I thoroughly enjoy reading through these suspension posts, Farkle. Thank you for putting all this information together in different posts. Subscribed to all of them.

Secondly, I'm currently looking at suspension options for my 340i RWD with track handling - so adaptive suspension and want to achieve a very mild drop, have more responsiveness, and less body roll. I'm debating between these choices right now - I'm also thinking of doing the F8x LCAs

1) M performance suspension
2) Dinan springs, bump stops, shockware
3) F8x ZCP springs (bump stops?)

I wondered which option would help me achieve my goals while not breaking the bank. I'd also like to fit the M performance front lip eventually too, so going too low wouldn't be conducive to that. Any help or thoughts are definitely appreciated!

[JaredG_F30]

Definitely not looking for a harsh ride but would like less body roll when cornering and something a more planted. I might just say F it and go Ohlins R&T.

Originally Posted by FaRKle!

It can be addressed that way, but the tradeoff is you're now overdamping and causing the ride to be more harsh overall.




Yes there are OE options from other models that can lower your car and maintain the same spring rate as you originally had. Do you want to maintain the original spring rate, or go stiffer some?

[FaRKle!]

Originally Posted by Jvac

I've read that the m performance suspension kit is not compatible with the adaptive suspension. Getbmwparts also says this in their sale post in the classifieds section. So if you did get it installed you'd have to get the adaptive function coded out. I was interested in the kit myself but the lack of information in that regard turned me away. If anybody has installed the performance suspension on a car with adaptive dampers, I'd love to hear their experiences. Opinions on the kit are otherwise very positive

I'm sure the reason you mentioned (having to code out/use a delete kit) is the reason why BMW says the M-Perf suspension isn't compatible. It physically fits in RWD cars.

Originally Posted by JaredG_F30

Definitely not looking for a harsh ride but would like less body roll when cornering and something a more planted. I might just say F it and go Ohlins R&T.

Depends on how you want to address body roll. With sway bars you can use OE type springs/dampers. If you don't want to use sway bars, and use higher spring rates instead, the stiffness you'll need will push you to coilovers or custom tuned dampers territory and is more difficult to avoid harshness.

[JaredG_F30]

Thanks for the input. I'll probably go with stiffer sway bars before suspension.

Originally Posted by FaRKle!

I'm sure the reason you mentioned (having to code out/use a delete kit) is the reason why BMW says the M-Perf suspension isn't compatible. It physically fits in RWD cars.




Depends on how you want to address body roll. With sway bars you can use OE type springs/dampers. If you don't want to use sway bars, and use higher spring rates instead, the stiffness you'll need will push you to coilovers or custom tuned dampers territory and is more difficult to avoid harshness.

[rcaso26]

I am currently running Koni Special Active struts with Eibach Pro Kit springs on my 2015 328i xdrive. The ride is really nice, but the suspension bottoms out on very big bumps or dips in the road. Will f80 bump stops remedy this issue?

I was thinking of maybe trying to pair the Konis with rwd msport springs to get a milder drop while maintaining the oem ride quality. Maybe the rwd 335i msport springs to compensate for the heavier xdrive transfer case.

Any advice would be greatly appreciated. I've gone through several suspension setups and all I want is a fairly comfortable ride without the huge xdrive wheel gap, something similar to the oem rwd height.

[a404freedom]

I drive an f32 m-sport that I've put H&R super sport springs on. I haven't replaced the shocks cause I'm not sure if I should do that or put in coilovers.

The ride isn't terrrible, I'd just like a tighter turns. My car is a daily driver and I won't be tracking it, i just wanna make sure I'm not making any mistakes. I know the factory shocks are going to go soon (47,500 miles on them as of now). Is it best to replace the shocks or pull both shocks and springs and install coilovers?

What shocks or coilovers are reviewed well? Ive read a lot on KWs and Bilsteins; are there others to consider? I'd like to keep it under $2000.

[gippy]

incredible post, and it made me go on youtube and learn more about ride frequencies and how to select in a more informed way what i need for my specific outcome.
ordering the bilstein b14's now!

many thanks FaRKle!