[rusty_sojah]

So i have a f33 (pre lci) with m sport suspension (no EDC). I added eibach pro-kit lowering springs, and the car handled amazingly and felt awesome as well. i think it was the best mix of comfy/sporty of any suspension i've ever owned. every car i've had prior to this was on coilovers and slammed with most likely incorrect dampening/rebound/spring rates etc...

so after riding around on the stock struts with the eibach springs for a while i felt like my punishing the car in corners was taking a toll on the struts and felt them getting softer and slightly sloppier so i decided to go with the b12 complete kit fully assembled with all new bits & different eibach lowering springs. i had the kit installed and the ride immediately felt more comfy and less sporty. the rear felt (feels) super unsafe at higher speeds when cornering, especially with someone sitting in the back or any heavy stuff in the trunk when i hit any sort of dip. even the slightest dip makes it really bouncy and feel like the rear is not bouncing with the flow of the road.

BTW i did double check that the b8 struts/shocks i received were for the correct car model etc..

i just had my car shop swap back in my original Eibach Pro-Kit Performance Springs (E10-20-031-08-22) to test hopefully the easiest solution and they feel a little less bouncy with a noticeable improvement but still i do not think the ride is nearly as sporty and capable as what it was with just the original bmw struts/shocks and the eibach pro springs above. after the install i took the local okinawan indy mechanic who did all the work, on a test ride yesterday so he could feel what i was talking about and i pushed the car a little and actually was able to show him exactly the feeling (got lucky on the road choice i guess) and he said it looked and felt like a togue setup and would be fun for drifting but that it wasn't a good cornering race track feeling at all... btw he is japanese and speaks like zero english and just builds and works on drift cars all day long so we don't have much dialogue

now here is my question/dilema. can i just get a new pair of the same rear OEM bmw shocks i had and swap them with the rear bilstein b8's or would there be more parts involved? i would like to be able to re-use all the new bits in the fully assembled kit i had ordered, since it wasn't cheap and hopefully fix this issue as easy as possible. or do i need to make sure all the struts/shocks are matching and not mixed, like front b8 and rear bmw??

in hindsight i should have just went coilovers if i would have known the ride handling would have gotten so much worse from this "upgrade" but i'm getting older and my wife always hated the feel of the slammed coilvers...

Any suggestions/recommendations? thanks,

Part numbers for reference:

Rear Bilstein b8 shock part - 24-264563

Rear OEM shock part - BMW 33526873767

[alohasurftoad]

I feel Eibach pro-kit with Bilstein B4 M-technik dampers is what you desire and will ride and handle better than your original good setup

[rusty_sojah]

Originally Posted by alohasurftoad

I feel Eibach pro-kit with Bilstein B4 M-technik dampers is what you desire and will ride and handle better than your original good setup

Thanks for this, do you know if i could just put these b4's in the rear and keep the current front b8's in place, or would that just make things even more weird feeling? I feel like the the car is still great in the corners and front feels stable.

[alohasurftoad]

Originally Posted by rusty_sojah

Thanks for this, do you know if i could just put these b4's in the rear and keep the current front b8's in place, or would that just make things even more weird feeling? I feel like the the car is still great in the corners and front feels stable.

I think it'd be fine to change just the rear if that's the primary cause of upset

[casualDIYer]

Originally Posted by rusty_sojah

now here is my question/dilema. can i just get a new pair of the same rear OEM bmw shocks i had and swap them with the rear bilstein b8's or would there be more parts involved? i would like to be able to re-use all the new bits in the fully assembled kit i had ordered, since it wasn't cheap and hopefully fix this issue as easy as possible. or do i need to make sure all the struts/shocks are matching and not mixed, like front b8 and rear bmw??

in hindsight i should have just went coilovers if i would have known the ride handling would have gotten so much worse from this "upgrade" but i'm getting older and my wife always hated the feel of the slammed coilvers...

One problem might be the rear anti-roll bar. As you upgrade from plushy BMW suspension to sporty suspension the anti-roll bar (ARB) often gets overlooked. On my 340, BMW was able to find a spaghetti noodle (12mm bar) and install that. Ironically, the part I upgraded it to was from the 440i (15mm bar). I wonder if other 440i owners went down this road as well of upgrading their rear ARBs. I'd do a little researching targeting the anti-roll bar issue on the 440. Fortunately it's not an expensive part. It's not hard to install but I'd call it physically demanding. A shop could probably do it within an hour.

I hear you on coilovers. After farting around with strut and spring combos on my car, I realised a common pain point was when I went to the track and wanted to adjust damping, the front was easy but the rear impractical. Of course had I just installed a set of KW V2s with remote adjusters on the rear that would have saved a ton of time and money. A 2025 project for sure.

[rusty_sojah]

Originally Posted by alohasurftoad

I feel Eibach pro-kit with Bilstein B4 M-technik dampers is what you desire and will ride and handle better than your original good setup

I'm not seeing anything that specifically says M-technik, are these it?

https://www.turnermotorsport.com/p-344473-tms344473/

[alohasurftoad]

Yes, m-technik = m-sport

[rusty_sojah]

Originally Posted by alohasurftoad

Yes, m-technik = m-sport

thanks, and yeah that now makes total sense

i know eibach doesn't release spring rates, but any idea if the rear springs in the Eibach Pro-Kit Performance Springs (E10-20-031-08-22) kit are the 11k type or perhaps they are closer to the 14k type??

i'm now looking at other coilover kits that are for sale here in japan and the rears are a choice of 11k or 14k spring rates. i'm guessing since these feel less sloppy/bouncy than the other eibachs i had on for just a few short weeks that they are more the 14k type, or maybe the sloppy feeling ones are even less than 11k perhaps??

[alohasurftoad]

@rusty, i am not sure about 11k or 14k numbers, but i believe the typical eibach pro-kit springs are 10%ish stiffer than stock. the difficult part is finding a damper to match a given spring's rate.

many have run Koni Special Active(Red) with eibach pro-kit, with a few dissatisfied. Eibach Pro-kit with Koni Sport Yellow or Bilstein B4 Sport may be a better combination.

on my F36 440i rwd, the current setup i have and am reasonably satisfied with is, M-Performance spring with Bilstein B6 HD yellow shocks in the rear and Stock(704/M-sport/sportline) springs over Koni Special Active(red) struts up front.

on large upward road undulations the car felt like it unweighted and floated too long before recovering. I believe it was caused by the M-performance rear spring rate being too high for the Koni SA rear damper, so i changed it to the stiffer Bilstein B6 HD and it works great.

the reason for keeping 704(m-sport/sportline springs) up front is because my front lip is too low. the Koni SA upfront being sportier thand the OEM sport struts, seems to match up reasonably well with the OEM sport springs up front.

due to different front and rear weight bias on different models, different combinations of setups may be more suitable for each.

a rebound and compression adjustable coilover would likely be better if you want precise tuning but most all coils have high(er) spring rates so they should feel firmer and feel more stiff than Koni SA(orYellow) or Bilstein B4 dampers under Eibach Pro-Kit springs.

[Polo08816]

Originally Posted by alohasurftoad

@rusty, i am not sure about 11k or 14k numbers, but i believe the typical eibach pro-kit springs are 10%ish stiffer than stock. the difficult part is finding a damper to match a given spring's rate.

many have run Koni Special Active(Red) with eibach pro-kit, with a few dissatisfied. Eibach Pro-kit with Koni Sport Yellow or Bilstein B4 Sport may be a better combination.

on my F36 440i rwd, the current setup i have and am reasonably satisfied with is, M-Performance spring with Bilstein B6 HD yellow shocks in the rear and Stock(704/M-sport/sportline) springs over Koni Special Active(red) struts up front.

on large upward road undulations the car felt like it unweighted and floated too long before recovering. I believe it was caused by the M-performance rear spring rate being too high for the Koni SA rear damper, so i changed it to the stiffer Bilstein B6 HD and it works great.

the reason for keeping 704(m-sport/sportline springs) up front is because my front lip is too low. the Koni SA upfront being sportier thand the OEM sport struts, seems to match up reasonably well with the OEM sport springs up front.

due to different front and rear weight bias on different models, different combinations of setups may be more suitable for each.

a rebound and compression adjustable coilover would likely be better if you want precise tuning but most all coils have high(er) spring rates so they should feel firmer and feel more stiff than Koni SA(orYellow) or Bilstein B4 dampers under Eibach Pro-Kit springs.

Good to hear someone is running the M-Performance springs (not M Sport/Sport) with the Bilstein B6 HD.

When my M Performance suspension sturts/shocks wear out, I'll probably replace them with the Bilstein B8 struts/shocks.

[alohasurftoad]

Originally Posted by Polo08816

Good to hear someone is running the M-Performance springs (not M Sport/Sport) with the Bilstein B6 HD. When my M Performance suspension sturts/shocks wear out, I'll probably replace them with the Bilstein B8 struts/shocks.

i actually believe the B6 may be more suitable than B8 when replacing the M-Performance struts, due to the B8 being a lot shorter and the B6 being the same length as OEM. since the M-Performance springs are only 10mm lower(than OEM) it would require the springs to be compressed a lot more to install the strut mount on the B8, compared to the B6, which would result in the M-Performance springs being more compressed after it is installed and the whole cup-kit being shorter.

[Polo08816]

Originally Posted by Polo08816

Good to hear someone is running the M-Performance springs (not M Sport/Sport) with the Bilstein B6 HD.

When my M Performance suspension sturts/shocks wear out, I'll probably replace them with the Bilstein B8 struts/shocks.

Originally Posted by alohasurftoad

i actually believe the B6 may be more suitable than B8 when replacing the M-Performance struts, due to the B8 being a lot shorter and the B6 being the same length as OEM. since the M-Performance springs are only 10mm lower(than OEM) it would require the springs to be compressed a lot more to install the strut mount on the B8, compared to the B6, which would result in the M-Performance springs being more compressed after it is installed and the whole cup-kit being shorter.

Depends on which OEM configuration you are talking about for RWD models.

M Sport / Sport suspension is 10mm lower than the base suspension.

M Performance suspension kit springs are 10mm lower than M Sport / Sport suspension springs so they are 20mm lower than the base suspension.

I think most literature says B8s are suitable for suspension that is lower than the M Sport / Sport suspenson


B6:
https://www.fcpeuro.com/products/bmw...n-bil-35217480
Position: Front, Standard Suspension without Electronic Suspension


B8:
https://www.fcpeuro.com/products/bmw...n-bil-35217862
Position: Front, For vehicles w/ M Sports Suspension(S704A) or lowering springs

[alohasurftoad]

Originally Posted by Polo08816

Depends on which OEM configuration you are talking about for RWD models. M Sport / Sport suspension is 10mm lower than the base suspension. M Performance suspension kit springs are 10mm lower than M Sport / Sport suspension springs so they are 20mm lower than the base suspension. I think most literature says B8s are suitable for suspension that is lower than the M Sport / Sport suspenson

B6:
https://www.fcpeuro.com/products/bmw...n-bil-35217480
Position: Front, Standard Suspension without Electronic Suspension

B8:
https://www.fcpeuro.com/products/bmw...n-bil-35217862
Position: Front, For vehicles w/ M Sports Suspension(S704A) or lowering springs

i hear ya. i've had M-Perf susp kit on my 428i F36 M-sport and just the rear M-Perf spring on my current 440i F36 M-sport and still feel that the B8 would be too short and would work better with a moderate lowering spring, such as H&R sport(and super sport) or Dinan. I feel minimal lowering springs such as Eibach Pro-Kit and M-Performance pair up better with an OEM length damper such as Bilstein B4/B6, Koni SA/Yellow.

that's just my opinion, so it'll be interesting to see the results when you swap your M-Perf dampers to B8. nothing better than a real review.

[rusty_sojah]

Originally Posted by Polo08816

I think most literature says B8s are suitable for suspension that is lower than the M Sport / Sport suspenson


B6:
https://www.fcpeuro.com/products/bmw...n-bil-35217480
Position: Front, Standard Suspension without Electronic Suspension


B8:
https://www.fcpeuro.com/products/bmw...n-bil-35217862
Position: Front, For vehicles w/ M Sports Suspension(S704A) or lowering springs

welp my experience with the b8's and Eibach (F11-20-031-01-VA) lowering springs was that it was much worse than my stock m-sport susp (BMW 33526873767) with E10-20-031-08-22 eibach springs. i put the E10's back on and it was/is moderately better in the rear but still not as tight and precise feeling as my stock with the E-10 eibach springs.

i guess i will try to get a pair of b4's swapped out in the rear and see if that puts it back to the feeling of my stock rear's with the E10 eibach springs. this to me was the best feeling around here where i drive so far.

in years past i had slammed very harsh feeling coilovers that would be great on some roads at moderately high speeds but were a little too tight for high speeds on certain stretches with bumpy roads. but having too soft of a rear shocks (b8's and springs) was an even scarier feeling at moderately high speeds.

if these rear b4's don't do the trick i'm going coilovers, just a little pissed i've once again wasted so much $$.

[Polo08816]

Originally Posted by rusty_sojah

welp my experience with the b8's and Eibach (F11-20-031-01-VA) lowering springs was that it was much worse than my stock m-sport susp (BMW 33526873767) with E10-20-031-08-22 eibach springs. i put the E10's back on and it was/is moderately better in the rear but still not as tight and precise feeling as my stock with the E-10 eibach springs.

i guess i will try to get a pair of b4's swapped out in the rear and see if that puts it back to the feeling of my stock rear's with the E10 eibach springs. this to me was the best feeling around here where i drive so far.

in years past i had slammed very harsh feeling coilovers that would be great on some roads at moderately high speeds but were a little too tight for high speeds on certain stretches with bumpy roads. but having too soft of a rear shocks (b8's and springs) was an even scarier feeling at moderately high speeds.

if these rear b4's don't do the trick i'm going coilovers, just a little pissed i've once again wasted so much $$.

I'm confused. I was under the impression that Bilstein B6 and B8 shocks are usually on the stiffer side.

[alohasurftoad]

B6/B8 are stiffer than B4. I'm speculating that the OP's Eibach Sportline(not pro kit)+B8 combo is not compliant enough (too stiff), which is good over smooth, but terrible over rough pavement.

When testing cars in the mountains, most reviewers set suspension to comfort to maintain contact patch over bumps.

B4 are a slightly sportier OEM replacement. Since OP desires how the Eibach Pro-kit over OEM worked, imo the B4 sport(or Koni SA) is the most suitably matched(arguably better) rear shock replacement, besides OEM.
.

[rusty_sojah]

Originally Posted by Polo08816

I'm confused. I was under the impression that Bilstein B6 and B8 shocks are usually on the stiffer side.

trust me i am perhaps more confused. i've had a few rock hard suspension setups in the past with various brands of coilvers on various cars (bmw's -plural- and toyota's - again plural- here in Okinawa & HI & MD), and this doesn't feel hard/stiff to me in the rear unless there is some wonky math with perhaps mismatched springs & shocks/struts or something else is screwed up. i didn't actually confirm the part numbers on the physical struts/shocks themselves but unless the seller reboxed a different product i just went off what the box said since the part is on the car already.

only thing i can figure is that the different length of the strut/shock and spring length/ spring rate really have a compounding effect one way or the other with the handling feel. but if this is true i am not sure why the car felt so capable with the stock m susp (whatever that actually is) and the Eibach Pro-kit, since this should have ultimately been a slight mismatch in height of stuff as well

[Polo08816]

Originally Posted by alohasurftoad

B6/B8 are stiffer than B4. I'm speculating that the OP's Eibach Sportline(not pro kit)+B8 combo is not compliant enough (too stiff), which is good over smooth, but terrible over rough pavement.

When testing cars in the mountains, most reviewers set suspension to comfort to maintain contact patch over bumps.

B4 are a slightly sportier OEM replacement. Since OP desires how the Eibach Pro-kit over OEM worked, imo the B4 sport(or Koni SA) is the most suitably matched(arguably better) rear shock replacement, besides OEM.
.

Originally Posted by rusty_sojah

trust me i am perhaps more confused. i've had a few rock hard suspension setups in the past with various brands of coilvers on various cars (bmw's -plural- and toyota's - again plural- here in Okinawa & HI & MD), and this doesn't feel hard/stiff to me in the rear unless there is some wonky math with perhaps mismatched springs & shocks/struts or something else is screwed up. i didn't actually confirm the part numbers on the physical struts/shocks themselves but unless the seller reboxed a different product i just went off what the box said since the part is on the car already.

only thing i can figure is that the different length of the strut/shock and spring length/ spring rate really have a compounding effect one way or the other with the handling feel. but if this is true i am not sure why the car felt so capable with the stock m susp (whatever that actually is) and the Eibach Pro-kit, since this should have ultimately been a slight mismatch in height of stuff as well

The Bilstein B6 and B8 struts/shocks have an internal bump stop so factory bump stops are not required. Did your mechanic re-install the factory bump stops? If he did, then your car may be bottoming out way before the end of your suspension travel range.

[rusty_sojah]

Originally Posted by Polo08816

The Bilstein B6 and B8 struts/shocks have an internal bump stop so factory bump stops are not required. Did your mechanic re-install the factory bump stops? If he did, then your car may be bottoming out way before the end of your suspension travel range.

The kit i purchased from Strutmonkey came with all new everything pre assembled. This was their description, "Our SM200 kit will lower your car about 1" and firm up the handling like an M3. It is a fully assembled kit using Bilstein B8 shocks and a set of Eibach springs. Your kit will arrive fully-assembled, 100% complete with the 20+ other parts needed for install - new OEM strut mounts, spring pads, shorter M3 style bumpstops, dust tubes, bearing protectors, washer, lubricant, and associated hardware."

It doesn't feel like it is bottoming out at all, it felt like way too much travel and not firm enough. The first real test i had was with my 100 lb wife sitting in the back and a 200 lb friend riding shotgun and i had verbally neen hyping up my car to him and it was his first ride and like 2 days after the install so i was excited and it was immediately noticeable that it was loose and bouncy feeling and felt uncomfortable and unsafe at speeds i would normal have been able to easily surpass. I thought it was the extra weight in the back perhaps since it was like the 1st time i can recall someone sitting there. But then a couple days later with me it felt pretty much the same like really no bueno. It is mucj improved with the other eibach springs back in that i was first using with just factory m susp but still not as good feeling as that. I really wish i could hit the undo button on this mod and go in a different direction. But maybe it is the universe telling me i shouldn't be time attacking every single drive i do ��

[rusty_sojah]

Noob question but on a car without edc does the sport mode do anything to the feel of the suspension? I know the steering wheel gets more feedback and less assist, i know the trans shift point change, and exhaust valves open but anything at all with the susp??

[alohasurftoad]

Originally Posted by rusty_sojah

Noob question but on a car without edc does the sport mode do anything to the feel of the suspension? I know the steering wheel gets more feedback and less assist, i know the trans shift point change, and exhaust valves open but anything at all with the susp??

I agree that it "feels" like the suspension changes in sport, but it is an impossibility with a passive suspension.

[alohasurftoad]

Originally Posted by Polo08816

The Bilstein B6 and B8 struts/shocks have an internal bump stop so factory bump stops are not required. Did your mechanic re-install the factory bump stops? If he did, then your car may be bottoming out way before the end of your suspension travel range.

on F3/4 series, the rear Bilstein B6/8 shocks are of standard design and require bumpstops, shorter ones for the B8.

as you can see from the B8 pic, a bumpstop is impossible up front