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      10-29-2011, 12:22 AM   #1
DaanBMW
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Lightbulb After M3 bits upgrade, will OEM sport susp be too soft

OK, so I'm slowly getting ready to put a bunch of M3 suspension parts on my e92 328i:
  • Front Control Arm/Tension Strut Retrofit Set
  • Aluminum Rear Guide Rod Set
  • Aluminum Rear Wishbone Set
  • Front Sway Bar Kit
  • Rear Sway Bar Kit
  • Rear Subframe Bushings

As with all e92's, the OEM sport susp is on the car. I'm beginning to think of what the impact of leaving the stock sport susp in with all these upgrades.

Any thoughts ? This will not tracked or anything, but I do like to drive it quite spirited especially during cornering.
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      10-29-2011, 10:45 AM   #2
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Your springs and dampers will have a better platform on which to do their jobs (less bind and deflection w/the M3 arms&bushings). Try it out. You can always change your springs&dampers later. I'm running those parts w/oe zsp springs and koni sport dampers. The springs are a little soft w/the koni's. I do wish I'd have installed the M3 sway bars w/the subframe bushings.
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      10-29-2011, 11:28 AM   #3
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Quote:
Originally Posted by cvc 22349a View Post
Your springs and dampers will have a better platform on which to do their jobs (less bind and deflection w/the M3 arms&bushings). Try it out. You can always change your springs&dampers later. I'm running those parts w/oe zsp springs and koni sport dampers. The springs are a little soft w/the koni's. I do wish I'd have installed the M3 sway bars w/the subframe bushings.
Yes, I also read the OEM sport springs aren't too bad but the shocks are a little weak... I just crudely compared my e92 with my former VW TDi (bilstein sports + h&r sports) and the VW is stiffer.

I was actually more keen on the sway bars then the control arms. My VW has a race RSB and cornering was day & night vs. just the sport susp pkg.

Last edited by DaanBMW; 10-29-2011 at 11:52 AM. Reason: "keen"
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      10-31-2011, 01:07 AM   #4
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If you don't mind me asking Im Curious as to what you paid for all the used bits.
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      10-31-2011, 01:12 AM   #5
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If you don't mind me asking Im Curious as to what you paid for all the used bits.
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      10-31-2011, 01:13 AM   #6
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OP consider doing coilovers over the OEM Setup..the thing about using the M3bits is it will highlight the OEM's weaknesses further..low spring rates.+ weak damping..and LSD should also be on your list..especially w upgraded rear sway and subframe bushings

EDIT: never mind I see you have a 328..not trying to bash..but most of these parts will be overkill for your car.

Last edited by tibra1; 10-31-2011 at 01:18 AM.
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      10-31-2011, 01:24 AM   #7
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Originally Posted by tibra1 View Post
OP consider doing coilovers over the OEM Setup..the thing about using the M3bits is it will highlight the OEM's weaknesses further..low spring rates.+ weak damping..and LSD should also be on your list..especially w upgraded rear sway and subframe bushings

EDIT: never mind I see you have a 328..not trying to bash..but most of these parts will be overkill for your car.




Thats what I thought most all of these parts will be over kill however if he does them he should probably look at a set of H&Rs and Koni Yellows. I think coils are overkill.
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      10-31-2011, 01:27 AM   #8
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Originally Posted by SIKH335 View Post
[/b]

Thats what I thought most all of these parts will be over kill however if he does them he should probably look at a set of H&Rs and Koni Yellows. I think coils are overkill.
Agree..honestly the front arms and sway for him..def yes..the rear arms?..meeh..and the rear sway and bushings..no way..the car doesnt experience no where near enuff torque to cause the deflection in these that a FBO tuned n54 sees.
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      11-01-2011, 03:50 PM   #9
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I can break traction in any corner with the 3L engine. I'm not sure the extra torque of the 3L turbo really does much more in cornering, where you already are rolling at reduced speed. Yes, it does have more torque. I see most of these upgrades as controlling the body roll, not to avoid the suspension being broken by the torque load. Yes, deflection is an issue, but I think vehicle mass is more of a cause then the extra available torque.

What I'm trying to understand is what the net effect would be of having the OEM sport susp stay in. A stiffer suspension would be a better fit - I agree with that, but what exactly would happen w/o the OEM ? I find it to be quite smooth for a normal ride, but in cornering or over bump at higher speeds it is already clearly insufficient unless you can really smoothen the corner really well.

I'm probably going to do what cvc 22349a suggested and evaluate later. BTW cvc 22349a - what exactly are you experiencing with the yellows + OE sp springs ?
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      11-01-2011, 05:21 PM   #10
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Quote:
Originally Posted by DaanBMW View Post
I can break traction in any corner with the 3L engine. I'm not sure the extra torque of the 3L turbo really does much more in cornering, where you already are rolling at reduced speed. Yes, it does have more torque. I see most of these upgrades as controlling the body roll, not to avoid the suspension being broken by the torque load. Yes, deflection is an issue, but I think vehicle mass is more of a cause then the extra available torque.
Hi DaanBMW, you may be asking two possible questions here. One, Is the ZSP suspension going to feel wrong, or perform worse, if you put the M3 stuff in? (I would say No to that one.) The other question you may be asking is, Are the M3 pieces going to significantly help with acceleration out of a corner, or is the ZSP suspension going to be overwhelmed anyway? (I don't know, but my suspicion is that you'll have to change springs & shocks to be satisfied.)

Note that a stiffer rear sway bar will lighten the inside rear tire a little more, and you'll have a little less power out of a corner with an open differential. The difference is very small, but since you seem to care about this specific case, you'll be going in the wrong direction.

Quote:
What I'm trying to understand is what the net effect would be of having the OEM sport susp stay in. A stiffer suspension would be a better fit - I agree with that, but what exactly would happen w/o the OEM ? I find it to be quite smooth for a normal ride, but in cornering or over bump at higher speeds it is already clearly insufficient unless you can really smoothen the corner really well.
Maybe, if you put in the rear sway bar, you could consider shortening the rear bump stops. The rear bar increases rear spring during a roll and moves you toward neutral steer. And when I say shorten I don't mean trim.
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      11-01-2011, 07:07 PM   #11
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Quote:
Originally Posted by DaanBMW View Post
I can break traction in any corner with the 3L engine. I'm not sure the extra torque of the 3L turbo really does much more in cornering, where you already are rolling at reduced speed. Yes, it does have more torque. I see most of these upgrades as controlling the body roll, not to avoid the suspension being broken by the torque load. Yes, deflection is an issue, but I think vehicle mass is more of a cause then the extra available torque.

What I'm trying to understand is what the net effect would be of having the OEM sport susp stay in. A stiffer suspension would be a better fit - I agree with that, but what exactly would happen w/o the OEM ? I find it to be quite smooth for a normal ride, but in cornering or over bump at higher speeds it is already clearly insufficient unless you can really smoothen the corner really well.

I'm probably going to do what cvc 22349a suggested and evaluate later. BTW cvc 22349a - what exactly are you experiencing with the yellows + OE sp springs ?

For me reducing the excessive rear subframe movement by installing the M3 bushings was priority #1 along with improving steering response/feedback and turn in (which is lost when switching to non-rft) with the M3 front control arms. The added neg camber reduces understeer a bit too. This does firm up the ride as do the Koni sports. I'm going to soften the rears next week as they 'feel' too stiff set at 1.25 turns for the zsp springs.
The zsp springs do feel a bit soft with the M3 bushings and the tires I'm running but it's plenty stiff for a DD. I know alot of guys will disagree (read Tibra1 ) with installing the M3 bushings and control arms w/o increasing spring stiffness but what's the point of increasing spring stiffness if you're still going to have excessive movement of the bushings? So, 'I' say try that first and go from there if needed.. My car handles and accelerates much more predictably than it did prior to these changes 'Luckyu' has driven my car; maybe he can explain it better?
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      11-01-2011, 10:34 PM   #12
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Quote:
Originally Posted by cvc 22349a View Post
The zsp springs do feel a bit soft with the M3 bushings and the tires I'm running but it's plenty stiff for a DD. I know alot of guys will disagree (read Tibra1 ) with installing the M3 bushings and control arms w/o increasing spring stiffness but what's the point of increasing spring stiffness if you're still going to have excessive movement of the bushings? So, 'I' say try that first and go from there if needed.. My car handles and accelerates much more predictably than it did prior to these changes 'Luckyu' has driven my car; maybe he can explain it better?
Let me try to remember how it felt. It felt very smooth on the highway, with a lot of body movement, but not bouncy or oscillating, as I feel in my car. Impacts from the road sounded and felt distant. So I would say very tight, I agree no issues or weird stuff from torque steer or anything like that (I hardly tested that though), and more slow body movement side to side than I'm used to. Not much up and down movement, very smooth.

So those are my impressions as I remember them! Hope it helps!

(My car is a 328i manual and CVC's is a 335i auto, plus I'm on performance springs plus I'm riding on bump stops!)
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      11-02-2011, 12:05 PM   #13
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Quote:
Originally Posted by luckyu View Post
Let me try to remember how it felt. It felt very smooth on the highway, with a lot of body movement, but not bouncy or oscillating, as I feel in my car. Impacts from the road sounded and felt distant. So I would say very tight, I agree no issues or weird stuff from torque steer or anything like that (I hardly tested that though), and more slow body movement side to side than I'm used to. Not much up and down movement, very smooth.

So those are my impressions as I remember them! Hope it helps!

(My car is a 328i manual and CVC's is a 335i auto, plus I'm on performance springs plus I'm riding on bump stops!)
What about body roll/mass transfer during cornering ? Given you have the M3 sways and he does not, and his is a bit heavier being a 335i... granted he has an LSD which helps in corner exits but not in braking.

(and what do you mean by riding on the bump stops ?)
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      11-02-2011, 12:57 PM   #14
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Quote:
Originally Posted by DaanBMW View Post
What about body roll/mass transfer during cornering ? Given you have the M3 sways and he does not, and his is a bit heavier being a 335i... granted he has an LSD which helps in corner exits but not in braking.

(and what do you mean by riding on the bump stops ?)
My experience with my own car was that performance springs reduced roll significantly. Adding the M3 sways on top of the perf. springs made no perceptible difference in my car. I was surprised, I thought I would feel the different rear sway bar. But I felt no difference.

Riding on bump stops means that the shock body contacts the bump stop when the car is at static (rest) height. One of my goals is to fix this by giving the car more travel.

Personally, I think that if you're most concerned about power out of a corner, AND you believe it can be fixed without an LSD, then there are two ways to improve it: reduce weight transfer by lowering the car, and soften the rear suspension relative to the front. Both will make the car worse, but it will get you closer to your goal.

I think that springs or shocks (or both) will make a lot more difference than any of the bushings you're considering. The rear sway bar will make a small difference in a direction opposite to your stated goal.

EDIT: To clarify, I am not recommending springs or shocks to fix power out of a corner. I don't think anything can properly fix that except an LSD.
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Last edited by luckyu; 11-02-2011 at 01:05 PM.
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      11-03-2011, 12:02 PM   #15
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Quote:
Originally Posted by luckyu View Post
My experience with my own car was that performance springs reduced roll significantly. Adding the M3 sways on top of the perf. springs made no perceptible difference in my car. I was surprised, I thought I would feel the different rear sway bar. But I felt no difference.

Riding on bump stops means that the shock body contacts the bump stop when the car is at static (rest) height. One of my goals is to fix this by giving the car more travel.
OK, so you are riding on the bumpstop to begin with ? The null effect of the RSB kinda makes sense then, the bumpstops are a very high-rate progressive spring on top of your actual spring so before the bar would transfer spring rate from the inner wheel to the outer your bumpstops are probably already stiffening the outer wheel suspension to virtually rigid.

Question: You said you have OEM performance springs. Why are they so low as to ride on the bumpstops ? Or should the stops have been swapped for shorter ones for these springs ?

____________
I guess a couple of clarifications are due: It's not the power out of the corner I'm mainly concerned about. What I am trying to improve is mainly the initial body movement when initiating cornering. You can improve it with a very early turn-in and flattening the curve, but not all corners are the same, and when I turn more abruptly the body movement is larger then on my older Golf. Out of the corner the bimmer being a RWD it really helps a lot more to re-gain neutral steering, up to the point where you can if you want to, to break traction/adherence.

Now to my experience to date, on a FWD Golf. I put in Bilstein sports + H&R sports, and no less then 3 RSB were on the car (not planned, but had to... long story). W/o the RSB the cornering was way worse, even with the upgraded suspension, but for sure it was miles from stock. The reason an RSB is way better then a v. stiff suspension is that it acts only when you need it, i.e. during cornering, and not all the time, thus it won't make the overall ride too harsh.

Other then the RWD dynamic which is clearly different between the Golf and the bimmer, I would think the net effect of the RSB would be similar. The other rear bits would reduce the suspension movements increasing the precision in cornering and overall.

I also had a front lower tie bar on the Golf, which improved steering precision to a whole new level. This is what I expect from the M3 front bits.

Now I agree the OEM sport susp is already too soft (while I do enjoy the "executive" ride quality in cruise mode). While thinking about upgrading, I really don't want to lower the car much more, it's already low enough that you have to look at every curb and estimate each road grade very carefully. 0.5" maybe... but beyond that no. (Yes, I am pondering an LSD as well... does it ever stop ?)

Anyways, here is roughly what my thinking is on this. Feel free to debate me about any of it. After all there is nothing like driving a car with these mods to assess realistically...
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      11-06-2011, 06:22 PM   #16
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Sorry, I lost track of this thread. My bad!

Quote:
Originally Posted by DaanBMW View Post
OK, so you are riding on the bumpstop to begin with ?
Yes, in front. In back I can't see but I calculate I have 1/8 to 1/4 inch between shock body and jounce bumper.

Quote:
The null effect of the RSB kinda makes sense then, the bumpstops are a very high-rate progressive spring on top of your actual spring so before the bar would transfer spring rate from the inner wheel to the outer your bumpstops are probably already stiffening the outer wheel suspension to virtually rigid.
You are right. The sway bar will add even more resistance to roll, but there was already enough, apparently.

Quote:
Question: You said you have OEM performance springs. Why are they so low as to ride on the bumpstops ? Or should the stops have been swapped for shorter ones for these springs ?
To the best of my knowledge, this is what happened. BMW offered a kit a couple years ago, called BMW performance suspension. It included shocks plus bump stops plus rear shock mounts, and sway bar bushings. Best I can tell, this kit was designed to work with the sport suspension springs.

But back then, in our infinite wisdom, a bunch of us here on the forum decided the kit was actually designed to use the yellow bmw performance springs, and installed them. That's what I did too. The upshot is I have springs that do not match my shocks or bump stops.

The newer BMW performance suspension kit includes yellow springs, and is meant to work with those springs.

Quote:
I guess a couple of clarifications are due: It's not the power out of the corner I'm mainly concerned about. What I am trying to improve is mainly the initial body movement when initiating cornering. ...
I don't like the body movement of the new cars either. But, I can't tell if you're going for lap times, or for a particular feel you want the car to have.

If you really are interested in reducing *initial* movement, then that is 99% shocks. Initial movement is allowed by (relatively) weak shocks.

Can you state your goals? Are you racing competitively, or are you trying to achieve something with your car that you *believe* will make it faster? I'm not saying you're wrong. What's your test for achieving your goal?

EDIT: OK, you stated your goals in the original post: spirited driving. I see another set of Bilsteins in your future.

Quote:
... You can improve it with a very early turn-in and flattening the curve, but not all corners are the same, and when I turn more abruptly the body movement is larger then on my older Golf. Out of the corner the bimmer being a RWD it really helps a lot more to re-gain neutral steering, up to the point where you can if you want to, to break traction/adherence.
OK.

Quote:
Now to my experience to date, on a FWD Golf. I put in Bilstein sports + H&R sports, and no less then 3 RSB were on the car (not planned, but had to... long story). W/o the RSB the cornering was way worse, even with the upgraded suspension, but for sure it was miles from stock. The reason an RSB is way better then a v. stiff suspension is that it acts only when you need it, i.e. during cornering, and not all the time, thus it won't make the overall ride too harsh.
Aha, so you care about ride comfort! Good to know...

Quote:
Other then the RWD dynamic which is clearly different between the Golf and the bimmer, I would think the net effect of the RSB would be similar. The other rear bits would reduce the suspension movements increasing the precision in cornering and overall.
You didn't mention what the RSB effect was. What the M3 RSB does in my mind is it makes the car neutral steer, increasing max mechanical grip. That's what the numbers say (but they don't include the effect of bump stops). I'm talking about high G steady state turns here.

Something to think about: no matter how soft or stiff your springs are, spring resistance at static is 800 lbs per corner. The softest spring you can imagine will still have 800 lbs initial resistance. Same for sway bars, although they ramp up faster. Initial resistance is zero. The thing that will actually control initial body movement is shocks.
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Last edited by luckyu; 11-06-2011 at 06:27 PM.
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      11-09-2011, 01:42 AM   #17
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Quote:
Originally Posted by luckyu View Post
EDIT: OK, you stated your goals in the original post: spirited driving. I see another set of Bilsteins in your future.
[snip]
Aha, so you care about ride comfort! Good to know...
My fillings are pretty good I guess, the susp was pretty stiff on my old car but the improved cornering I felt was worth it. However for most city driving the nice feel of the OEM sp susp is not the be discarded for just any stiff setup or car slam.

Quote:
Originally Posted by luckyu View Post
You didn't mention what the RSB effect was. What the M3 RSB does in my mind is it makes the car neutral steer, increasing max mechanical grip. That's what the numbers say (but they don't include the effect of bump stops). I'm talking about high G steady state turns here.
I thought I did mention the RSB effects, maybe indirectly: improved body roll, w/o the overall further stiffening of the ride, which is what stiffer shocks+springs do. If the M3 sways make it more neutral, that's what I'm after !

Quote:
Originally Posted by luckyu View Post
Something to think about: no matter how soft or stiff your springs are, spring resistance at static is 800 lbs per corner. The softest spring you can imagine will still have 800 lbs initial resistance. Same for sway bars, although they ramp up faster. Initial resistance is zero. The thing that will actually control initial body movement is shocks.
The 800lbs per corner is the force that the springs have to support at rest. It has no relevance when compression/load occurs, the spring rate is what counts then (as well as upon extension/unload). Given my previous experience w/ and w/o the RSB, the improvement of having one were tremendous.


The more I think about it the more I think I will just do it and see, maybe test drive an e92 with an upgraded shock+springs package or coilovers - short of finding a car with all the M3 parts on it & the OEM sport susp.

Too bad you and cvc 22349a are in the bay area - should've read all this before buying the car, that's where I got it from...
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      11-09-2011, 12:32 PM   #18
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Quote:
Originally Posted by DaanBMW View Post
My fillings are pretty good I guess, the susp was pretty stiff on my old car but the improved cornering I felt was worth it. However for most city driving the nice feel of the OEM sp susp is not the be discarded for just any stiff setup or car slam.
I agree. I don't want to compromise driving enjoyment at all, so I don't want a suspension to feel "hard". (Other than that, I believe that a firm suspension is more comfortable than a pillowy one, as I'm sure you do!)

Quote:
I thought I did mention the RSB effects, maybe indirectly: improved body roll, w/o the overall further stiffening of the ride, which is what stiffer shocks+springs do. If the M3 sways make it more neutral, that's what I'm after !
What opened my eyes was looking at the numbers, and the numbers say that the M3 bar -- if we ignore bump stops -- snap the car into balance. It takes an understeering car like the E9X and makes it into a 50/50 car. This is true at many different rates of main spring, as long as one sticks to relatively equal F/R spring rates.

Perhaps you would like to look at what Orb has written in this forum. He can be abusive and incoherent but he is often correct. There is also a spreadsheet he contributed that was uploaded by Mr.5. It's buried in some thread somewhere here.

Using the spreadsheet has been eye-opening for me.

Also. There is a powerful way to search the forums that is much better than the built in search. If you don't already know about it, it's very helpful for scanning the forums. Use Google like this:

orb roll bar site:e90post.com

and you'll get hits restricted to the web site.

Quote:
The 800lbs per corner is the force that the springs have to support at rest. It has no relevance when compression/load occurs, the spring rate is what counts then (as well as upon extension/unload). Given my previous experience w/ and w/o the RSB, the improvement of having one were tremendous.
High rate springs do reduce movement. The more initial the movement, the less efficiently a high spring rate will stop it.

(800 + 300) / (800 + 150) = 1.16

Double the front main spring rate and you reach 16% more resistance after one full inch of travel. I tell you it's the shocks, man!

The rear sway bar although expensive is a good mod and I think you should do it. I'm just talking about the role shocks have in controlling movement.
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