Eibach + Dinan + New Shocks

[SandM3]

Hello all, and thanks in advance for all replies and advice.

I think I made a mistake but could turn out to be a good idea.
Calling all masters, rzm3 Malek@MRF Remonster and TimberWolf_3063 (apologies in advance for the Spam but I'm in a tight spot)

I have a 2010 LCI e90 with EDC (non-ZCP) and bought eibach lowering springs.
For the front I bought the e36 bumpstops and will shave the mounts.
I bought the dinan kit for gaining suspension travel in the rear.
And since the rear shocks are still the factory ones and they are tired I bought new shocks. (got new ones for the front 2 years ago)
However I messed up and bought ZCP shocks 33522284315 instead of the normal ones 33522284314. (for the rear yes)

Before I return them and ask for the normal ones, allow me to ask the following:
Should I keep the rear ZCP shocks instead to make up for the lost travel of the eibach springs? Or is it gonna change the feel of the car too much?
Eibachs drop 15 mm in the rear
Dinan drop 7 mm (still missing 8 mm)
ZCP drop 10 mm as far as I know (will be an extra 2 but I can use on the existing parts to make up for it)

Do ZCP shocks change much more other than length? Please bear in mind I have almost new non-ZCP shocks in front.

Many thanks in advance!

[SandM3]

Bump? I'm really in dire need of expert help here. : (

[GORDON.M3]

ZCP shocks on a non-ZCP car are a significant improvement regardless of what spring you plan on using with it.

The ZCP shocks can handle the Eibach springs with no problem.

[SandM3]

Originally Posted by GORDON.M3

ZCP shocks on a non-ZCP car are a significant improvement regardless of what spring you plan on using with it.

The ZCP shocks can handle the Eibach springs with no problem.

Hey Gordon. Thank you so much for the input.
Care to elaborate a bit? Please note I am not changing the front shocks as they are almost new. Only changing the rears.
ZCP and Normal shocks cost the same here in EU.
What are the implications in terms of height? My understanding is that lowering springs alone mess up the shocks because of the extra "forced" compression. Do these ZCP shocks offset the lowered springs? How does this interfere with my plan to put the dinan mounts on the rear?

Again, really appreciate the input. I can see you chime in a lot here in the forums so really appreciate you taking your time.

[GORDON.M3]

Originally Posted by SandM3

Hey Gordon. Thank you so much for the input.
Care to elaborate a bit? Please note I am not changing the front shocks as they are almost new. Only changing the rears.
ZCP and Normal shocks cost the same here in EU.
What are the implications in terms of height? My understanding is that lowering springs alone mess up the shocks because of the extra "forced" compression. Do these ZCP shocks offset the lowered springs? How does this interfere with my plan to put the dinan mounts on the rear?

Again, really appreciate the input. I can see you chime in a lot here in the forums so really appreciate you taking your time.

Both OE/ZCP Shocks, won't change or offset the height at all. The height is strictly determined by the spring usually.

In terms of strictly the rear for this particular car, ZCP Springs and Eibach springs are essentially the same height. In experience, the Eibach springs felt a little bit higher than the OE ZCP springs in the rear.

[SandM3]

Originally Posted by GORDON.M3

Both OE/ZCP Shocks, won't change or offset the height at all. The height is strictly determined by the spring usually.

In terms of strictly the rear for this particular car, ZCP Springs and Eibach springs are essentially the same height. In experience, the Eibach springs felt a little bit higher than the OE ZCP springs in the rear.

Would you say that the ZCP shocks come ready for the lowered springs, then?

Since I am not changing the front shocks, what would you do?
Use the ZCP shocks with stock mounts and just put eibach springs?
Or return the ZCP shocks for stock and just use the dinan?

I am really afraid that mixing normal in front with ZCP in rear will mess up the car feel.

[GORDON.M3]

Originally Posted by SandM3

Would you say that the ZCP shocks come ready for the lowered springs, then?

Since I am not changing the front shocks, what would you do?
Use the ZCP shocks with stock mounts and just put eibach springs?
Or return the ZCP shocks for stock and just use the dinan?

I am really afraid that mixing normal in front with ZCP in rear will mess up the car feel.

Yes. ZCP Shocks are definitely more spec'd for lowered applications, meaning it would work much better with lowering springs than it would if non-ZCP.

Mixing front and rear would not really throw off the car, are you tracking it?
Even if you are, the difference would be negligible. Don't mix the springs though, if you are running lowering springs, make sure the front and rear are the same brand.

[SandM3]

Originally Posted by GORDON.M3

Yes. ZCP Shocks are definitely more spec'd for lowered applications, meaning it would work much better with lowering springs than it would if non-ZCP.

Mixing front and rear would not really throw off the car, are you tracking it?
Even if you are, the difference would be negligible. Don't mix the springs though, if you are running lowering springs, make sure the front and rear are the same brand.

Gordon, you are a life saver.
Yes I do track the car. But not that intensively, otherwise I would have ditched the whole suspension.
I checked with bimmerworld and they agree with you. Using the ZCP shocks makes more sense for the lowered springs.
Yes. I won't be mixing springs.
My last question is about the dinan rear mounts. What should I do there? Still use them or use the stock mounts?

[M3SQRD]

My only concern with mixing dampers is it could make the front and rear of the car to feel disconnected. The zcp shocks are more aggressive tuned so, as an example, you’re making a left hand turn which causes the chassis to roll. With similarly tuned dampers, the front and rear roll rate will be damped out with a similar amount of time but the standard F and zcp R the rear roll rate is damped out more quickly, leaving the front to continue to roll for a longer time duration. With your position in the car being located in front of the center of gravity you’ll get a feeling where the front is moving/rotating more than the rear. Thus, the disconnected feeling and it’ll have an impact on not just roll but pitch and heave chassis motions (sprung weight motions relative to the road) and wheel assembly responses (unsprung weight is the motion of the wheel assemblies moving relative to the chassis) also will be more quickly damped out at the rear than the front giving you the sensation that the front is still moving up and down after the rear motions have been fully damped out. Personally, I would not mix - standard/standard or zcp/zcp.

[SandM3]

Originally Posted by M3SQRD

My only concern with mixing dampers is it could make the front and rear of the car to feel disconnected. The zcp shocks are more aggressive tuned so, as an example, you’re making a left hand turn which causes the chassis to roll. With similarly tuned dampers, the front and rear roll rate will be damped out with a similar amount of time but the standard F and zcp R the rear roll rate is damped out more quickly, leaving the front to continue to roll for a longer time duration. With your position in the car being located in front of the center of gravity you’ll get a feeling where the front is moving/rotating more than the rear. Thus, the disconnected feeling and it’ll have an impact on not just roll but pitch and heave chassis motions (sprung weight motions relative to the road) and wheel assembly responses (unsprung weight is the motion of the wheel assemblies moving relative to the chassis) also will be more quickly damped out at the rear than the front giving you the sensation that the front is still moving up and down after the rear motions have been fully damped out. Personally, I would not mix - standard/standard or zcp/zcp.

Thank you for that amazing write up. You were able to eloquently summarise exactly my fear.
Allow me to offer a counterpoint:
Putting the eibach springs will also change the "natural balance" of the car because of the compressed shocks. How I'm offsetting it:
In the front doing the shaved mounts + E36 bump stops will gain 16mm from the 20mm the springs lower.
In the back the dinan top mounts only give back 7mm from the 15mm the springs lower.
From my reading, the feedback from Gordon and the feedback from bimmerworld, the main change in the ZCP comes from the springs, the valving and compression are mostly to adapt to the lowered springs and as such it is actually recommended to use ZCP with lowered springs.

So now the question is what will make the car worse/more unbalanced: riding on compressed rear shocks but matching both non ZCP or mixing ZCP and stock? Neither is perfect, I know. But what's worse?

I am super undecided as I cherish the driving feel a lot.

[M3SQRD]

Originally Posted by SandM3

Thank you for that amazing write up. You were able to eloquently summarise exactly my fear.
Allow me to offer a counterpoint:
Putting the eibach springs will also change the "natural balance" of the car because of the compressed shocks. How I'm offsetting it:
In the front doing the shaved mounts + E36 bump stops will gain 16mm from the 20mm the springs lower.
In the back the dinan top mounts only give back 7mm from the 15mm the springs lower.
From my reading, the feedback from Gordon and the feedback from bimmerworld, the main change in the ZCP comes from the springs, the valving and compression are mostly to adapt to the lowered springs and as such it is actually recommended to use ZCP with lowered springs.

So now the question is what will make the car worse/more unbalanced: riding on compressed rear shocks but matching both non ZCP or mixing ZCP and stock? Neither is perfect, I know. But what's worse?

I am super undecided as I cherish the driving feel a lot.

Owning both a ‘09 non-comp (since taking delivery in 6/08) and ‘12 comp (since taking delivery in 11/11) e92 M3s, I can tell you the ride quality and damping performance are worse and improved, respectively. The suspension tuning is not identical.

As long as there’s sufficient suspension travel, the damper couldn’t care less whether lowered or not. The internal travel doesn’t increase when you adjust external features. The usable compression travel lost can’t fully be regained because you’ve now increased the probability the valve stack will internally bottom out. The valve stack doesn’t care where it starts from because it’s a passive item that develops a force due to the pressure differential across the valve stack as the piston moves with velocity (Fdamp = c*delta pressure). Stock travel is limited to begin with and the stock bump stops are already used to limit max travel of the piston rod/valve stack. Again, regaining external travel doesn’t change the fixed amount of internal travel available. Droop travel and damper body length determines the amount of internal travel.

[SandM3]

Originally Posted by M3SQRD

Owning both a ‘09 non-comp (since taking delivery in 6/08) and ‘12 comp (since taking delivery in 11/11) e92 M3s, I can tell you the ride quality and damping performance are worse and improved, respectively. The suspension tuning is not identical.

As long as there’s sufficient suspension travel, the damper couldn’t care less whether lowered or not. The internal travel doesn’t increase when you adjust external features. The usable compression travel lost can’t fully be regained because you’ve now increased the probability the valve stack will internally bottom out. The valve stack doesn’t care where it starts from because it’s a passive item that develops a force due to the pressure differential across the valve stack as the piston moves with velocity (Fdamp = c*delta pressure). Stock travel is limited to begin with and the stock bump stops are already used to limit max travel of the piston rod/valve stack. Again, regaining external travel doesn’t change the fixed amount of internal travel available. Droop travel and damper body length determines the amount of internal travel.

Hot damn. Those are some serious writing chops. Thank you for the write up.
I shall return the shocks and go for the normal ones then. Mixing ZCP and normal was really irking me.
Thank you sir.

I shall do a write up once I install everything and name you and Gordon as honorary patrons of this glow up on the lower down. ahah

[vitalsigns]

With all those new/upgraded parts, why didn't you just go with a set of quality coilovers, such as the Ohlins R&T? Big difference in price? Desire to retain EDC?

[GORDON.M3]

I've driven both ZCP and non-ZCP cars, and the ZCP car feels more planted/responsive but not by much.

I wouldn't conclude that it's largely because of the suspension tuning but you need to also take into consideration that the ZCP came with wider wheels in the front and rear. Every .5" width you go wider on the wheel has a tremendous impact from an overall handling perspective.

Now when we are talking about taking the ZCP and Non-ZCP out of place and applying aftermarket springs/hardware to it, the "original tuning" that it once had goes out the door. The most ideal setup would be to match front and rear, but in your situation now I wouldn't waste money on getting ZCP fronts to match the rears. What I would do is enjoy it for now and upgrade to coilovers down the road.

The Dinan mounting hardware would be a great way to refresh old parts on a 10+ year old chassis, so yes, install them.

[SandM3]

Originally Posted by vitalsigns

With all those new/upgraded parts, why didn't you just go with a set of quality coilovers, such as the Ohlins R&T? Big difference in price? Desire to retain EDC?

Hi there. Yes it was the EDC and cost. Let me share my thought process with you and get your feedback:

rear EDC shocks 800 (i got free new ones in the front)
eibach springs 250
shaving mounts and dinan mounts 200

all in all 1250

cheapest edc coilovers run at 3000

billstein EDC compatible shocks front and rear cost 2000
+ springs 250
total 2250

I really need EDC though. Roads in Portugal are a mess.

Please feel free to call me a cheapskate and tell me I should have gone for the B6. ahah

[SandM3]

Originally Posted by GORDON.M3

I've driven both ZCP and non-ZCP cars, and the ZCP car feels more planted/responsive but not by much.

I wouldn't conclude that it's largely because of the suspension tuning but you need to also take into consideration that the ZCP came with wider wheels in the front and rear. Every .5" width you go wider on the wheel has a tremendous impact from an overall handling perspective.

Now when we are talking about taking the ZCP and Non-ZCP out of place and applying aftermarket springs/hardware to it, the "original tuning" that it once had goes out the door. The most ideal setup would be to match front and rear, but in your situation now I wouldn't waste money on getting ZCP fronts to match the rears. What I would do is enjoy it for now and upgrade to coilovers down the road.

The Dinan mounting hardware would be a great way to refresh old parts on a 10+ year old chassis, so yes, install them.

Thank you for chiming in again. I really appreciate how supportive this community is.
I bough all suspension "wear and tear" components: mounts, the tiny metal disks, the shock disk bushings/rubbers, bump stops, nuts and bots, top and bottom spring pads, all that. No bushes for the arms - will do a full powerflex rebuild in a few years
Mine's a 2011 with 80k miles.

I'll be documenting part wear and tear on all parts and making a complete post on it, while documenting both the before and after looks. I have to give back to the forum, after all.

I just returned the zcp shocks and ordered the stock ones. I do need to buy them as the rear is unnervingly jumpy.

[Reddevils7]

Are there actual hardware differences between non-zcp and zcp dampers if they both have EDC? I thought it was only the software tuning aspect in sport to make them adaptive instead passive. The only hardware difference between the two suspensions are the springs sizes??