[thakid22]

Originally Posted by zhp43867

I don't disagree with what you say in theory. However, replacing E90 RSMs with stiffer units has been previously documented to reduce the "E90 bounce" in cars that were very unlikely to have worn stock RSMs.

http://www.1addicts.com/forums/showthread.php?t=383796

I never said the Dinan RSMs fix the problem, moreover that they seem to contribute to the overall fix. You told me that if I thought Dinan RSMs fix all the suspension problems, I should stuff it. Ironically, I never said that.

I'll be moving on now. Didn't intend to be sucked into an argument (or suck you into one).

This right here....

[cvc 22349a]

Originally Posted by DrRobert

I wonder if these shock mounts OP is referring to would benefit someone who already has the M3 SF bushings and other suspension bits.

Yes, I have both. The firmer upper rsm's, Dinan or Powerflex, remove the squish that occurs with the soft oem rsm's. The shocks react quicker to inputs with firmer rsm's and the little bounce felt over bumps with the oem's goes away with firmer rsm's.

[thakid22]

Originally Posted by FCobra94

How much stiffer do you want it to be? The OEM piece is already hard as a rock. Almost no difference between the new one I put in and the one I took out w/ ~56k miles on it.

My old one was hard too. Like you, I found that the replacement felt darn similar, if not the same. However, looking at the design, I wouldn't be surprised if it flexed quite a bit right at the spot where the flange on the shock shaft meets the whole in the mount under high piston speeds.

That lower mount is pretty big, but the load looks to be concentrated right around the center, rather than evenly dispersed.

Still you may be right. Maybe there is little to gain with that lower mount... It seems all of the polyurethane e90 kits skip that mount. Perhaps that's why.

[ajsalida]

There are close to 50 rubber bushings in the rear e9x suspension/subframe (yes I counted them all). Most of them are too soft when you start pushing things. Yes the RSM's are weak, so are the subframe bushings, but overall the RSB's are one of the weakest links esp once you start modding.

OP, you brought up the M3 subframe bushings and indicated people may not need to replace them if they replace the RSM's with your DINAN part. That is just not correct, they have almost nothing to do with each other, aside from being in the rear of the car. I don't know any other way to say it. If they have replaced shocks with new stiffer ones then maybe they will want to replace the RSM's with stiffer also, or maybe not. However having extra travel is not going to do much if anything at stock ride height, or even moderately lowered. It is hard to bottom the rear out if you have proper length bump stops in place.

I am glad you fixed what seemed like a problem with your car, as I said. But what you did was a very good example of what I was also talking about. You replaced your shocks with something stiffer, so the next weakest thing became more apparent. I did not know your RSM's were new, but that just points again to the fact that the bushings in this car in this area are weak points once you start upgrading, and fixing one starts a chain of needing to fix them all. I suspect you have not got your car to a place yet where the RSB weakness is apparent.

What I was trying to do, was tell people who do have legitimate problems with RSB's, that replacing RSM's will not solve their RSB problem, as you were implying. That just won't happen. If they have a RSM problem then replacing RSM's will clearly help. If there are/were a bunch of 1 series folks who were all replacing RSB's when just replacing RSM's would fix their problem, then I feel sorry for them.

What you were saying was like someone saying "I put on a new muffler and fixed my wastegate rattle problem". Well no he didn't, he put on a new muffler and now he can't HEAR his wastegate problem. Yes both parts of the exhaust system but unrelated. And unfortunately like RSB's vs RSM's, RSB's are very expensive to fix compared to RSM's. But if he had a bad muffler he needed a new muffler, it just did not fix his other problem too, though it would be nice to think so. Make sense?

[ajsalida]

Originally Posted by thakid22

Agreed. My only problem with the E9x rear suspension is the rear bounce on bumps.
During my research to remedy this bounce, the rear subframe bushings have been repeatedly fingered as the culprit. Many a thread, said the only way to get rid of the bounce is via M3 rear bushings.

This thread is simply here to state that the bounce can be fixed without the m3 parts. Hallelujah!
Let me my make myself clear, though. The M3 rear subframe mounts do indeed offer additional benefits beyond the alleviation of bounce.

I am just ecstatic that the horrid bounce is gone.

M3 bushings may one day find a home at my rear subframe, as I love making upgrades.
Mind you, there is still room left on the table for improvement. You'll have to forgive my overzealous enthusiasm for these Dinan mounts, though. They took the one single thing I hated most about the E9x platform and fixed it expertly. That bounce is ridiculous.
Anyway, that's neither here nor there, as it is gone now. I digress.

OK this is a much better description of what you did and why. I think once you get comfortable with your car and maybe drive it harder or over rougher surfaces, then stiffen up the RSB's one way or another you will be even more amazed. I also think many people believe they have a RSB problem (they actually do) but what they are feeling is actually soft RSM's.

I hope you see why I was trying to tell people that stiffer RSM's do not fix the true RSB problem. And rear bounce or pogo-ing is not what I would describe as a RSB problem. RSB you can feel the subframe wiggling/twisting around mid corner over bumps or under power, no or mostly not vertical motion, very disquieting.

Maybe it is a 335 vs 330 issue but I have Konis + eibachs, rear m3 bar, Whiteline RSB inserts, etc. and have no issues with the stock RSM's or any rear bounce. And I live in an area with very bad roads and washboard surfaces. I also have pretty soft tires, Conti DWS that soak up a lot of small harshness, so perhaps that filters out some of the bounce.

Originally Posted by thakid22

Agreed. My only problem with the E9x rear suspension is the rear bounce on bumps.
During my research to remedy this bounce, the rear subframe bushings have been repeatedly fingered as the culprit. Many a thread, said the only way to get rid of the bounce is via M3 rear bushings.

This thread is simply here to state that the bounce can be fixed without the m3 parts. Hallelujah!
Let me my make myself clear, though. The M3 rear subframe mounts do indeed offer additional benefits beyond the alleviation of bounce.

I am just ecstatic that the horrid bounce is gone.

M3 bushings may one day find a home at my rear subframe, as I love making upgrades.
Mind you, there is still room left on the table for improvement. You'll have to forgive my overzealous enthusiasm for these Dinan mounts, though. They took the one single thing I hated most about the E9x platform and fixed it expertly. That bounce is ridiculous.
Anyway, that's neither here nor there, as it is gone now. I digress.

This definitely makes sense. Not sure why people are getting confused by your comments. In addition to the mods in my sig, I have the Dinan rear upper shock mounts too. I put those in primarily because the stock pieces looked like crap and didn't want to put OEM bushings back in if they were going to fail again after only ~50k miles.

having said that, the rear is perfect; I just wish the front end felt as "tight" and didn't bounce when trying to deal with long dips at highway speeds, etc. Not sure what could be causing this in my case.

Either way, the problem with replacing anything on these cars with a "better" part is that it quickly points out other weak links in the system. What small benefits you do get makes you quickly realize that the car doesn't necessarily feel any more "complete" then it did before; this is especially true with suspension bushings (I'd imagine more so with a rsb swap). Luckily upgrading to the Dinan pieces was positive all the way around. No negatives whatsoever.

[DrRobert]

Originally Posted by cvc 22349a

The firmer upper rsm's, Dinan or Powerflex, remove the squish that occurs with the soft oem rsm's. The shocks react quicker to inputs with firmer rsm's and the little bounce felt over bumps with the oem's goes away with firmer rsm's.

And rear bounce or pogo-ing is not what I would describe as a RSB problem. RSB you can feel the subframe wiggling/twisting around mid corner over bumps or under power, no or mostly not vertical motion, very disquieting.

I appreciate the information in this post. My car has both pogo-ing over straight bumps and sideways wiggle over bumps in turns. It is actually in the shop getting M3 SF bushings now but now I'll know what to blame next (shock mounts or the shocks themselves) if I still have the vertical bounce after upgrading the SF bushings. Thanks guys!

[ajsalida]

To put this all in maybe a better perspective, consider how the various cornering, braking, bumps, etc type of loads from tires are transmitted to the unibody.

You have the 2 upper shock mounts, these get mainly vertical loads almost directly in line with tires/wheels movement but only when relative vertical motion/forces between wheel and unibody happens. Shocks do not take any static weight IOW, but they resist compression and extension of the spring sitting on the lower control arm.

Then you have springs via the 2 upper spring perch/pads. This is where the most static weight is taken up, but also vertical compression/extension loads of the spring.

Then you have 4 rear subframe bushings. Unfortunately these are the only things transmitting all of the remaining dynamic loads from the various links to the subframe and then to the unibody. Also partially transmits loads from springs and lower shock mounts, since they attach to lower links. And then the loads from the diff (again more bushings but inside the sub frame) and axles/hubs under power and decel/braking. And that is it, 8 points of contact 4 of which are RSB's. Even the rear sway bar bushings/brackets, which on other cars attach to the unibody, are on the subframe. So anti-roll bar loads are also totally contained inside the rear subframe before getting transmitted to the rest of the car.

The OEM RSB's are so friggin' soft, and have so many different loads on them, and are configured in such a way that they actually let the subframe move in all six possible degrees of freedom. Meaning forward/back, up/down, side-side, and rotate/twist around each of the three axis. That is maybe great for isolation purposes under very light loads. Not so good under more aggressive situations.

So there is a lot of stuff going on, and maybe it is easy to see what happens once you stiffen up things like RSM's and shocks sway bars etc, without addressing RSB's.

Just think about the links. 5 each side, 2 bushings each link, that is 20 bushings right there. Suppose you stiffen them all up with fancy M3 bits, but don't do the RSB's. They stay in place relative to the subframe much better now, but transmit higher loads to the subframe, causing greater movement of the subframe relative to the unibody.

[thakid22]

Originally Posted by ajsalida

There are close to 50 rubber bushings in the rear e9x suspension/subframe (yes I counted them all). Most of them are too soft when you start pushing things. Yes the RSM's are weak, so are the subframe bushings, but overall the RSB's are one of the weakest links esp once you start modding.

OP, you brought up the M3 subframe bushings and indicated people may not need to replace them if they replace the RSM's with your DINAN part. That is just not correct, they have almost nothing to do with each other, aside from being in the rear of the car. I don't know any other way to say it. If they have replaced shocks with new stiffer ones then maybe they will want to replace the RSM's with stiffer also, or maybe not. However having extra travel is not going to do much if anything at stock ride height, or even moderately lowered. It is hard to bottom the rear out if you have proper length bump stops in place.

I am glad you fixed what seemed like a problem with your car, as I said. But what you did was a very good example of what I was also talking about. You replaced your shocks with something stiffer, so the next weakest thing became more apparent. I did not know your RSM's were new, but that just points again to the fact that the bushings in this car in this area are weak points once you start upgrading, and fixing one starts a chain of needing to fix them all. I suspect you have not got your car to a place yet where the RSB weakness is apparent.

What I was trying to do, was tell people who do have legitimate problems with RSB's, that replacing RSM's will not solve their RSB problem, as you were implying. That just won't happen. If they have a RSM problem then replacing RSM's will clearly help. If there are/were a bunch of 1 series folks who were all replacing RSB's when just replacing RSM's would fix their problem, then I feel sorry for them.

What you were saying was like someone saying "I put on a new muffler and fixed my wastegate rattle problem". Well no he didn't, he put on a new muffler and now he can't HEAR his wastegate problem. Yes both parts of the exhaust system but unrelated. And unfortunately like RSB's vs RSM's, RSB's are very expensive to fix compared to RSM's. But if he had a bad muffler he needed a new muffler, it just did not fix his other problem too, though it would be nice to think so. Make sense?

Maybe I didn't make myself clear. Perhaps I added confusion by mentioning M3 rear subframe mounts. But let me try this again.
I feel that non M3 E9x models have too much bounce at the rear. It doesn't matter if its a 335i sport with 0k miles or a base 325i with 230k miles. All of these cars displayed what I feel to be too much bounce. Worn parts are not the issue, as new E9x do it too.

I know terms like "too much bounce" are highly subjective. What one person feels to be too much, the next may consider negligible.
But for a moment, let's treat the rear bounce as a fact.
I am simply stating that the addition of Dinan mounts got rid of the bounce. The tail end feels flat,level, composed, and does not suffer from the wild oscillations over bumps that the BMW designed mounts suffer. This also is a fact.

I never intended to imply that the Dinan mounts can replace the M3 rear bushings in all circumstances. That assertion would certainly be false.
I only considered M3 bushings because the back end of the car was bouncing over bumps.
After installing the dinans, the bounce is not noticeable and the rear end feels normal.

So in the quest to eliminate bounce, I no longer covet M3 bushings. And yes the dinans are a viable alternative when solely seeking to eliminate bounce. I stand by this statement, wholeheartedly.

I also acknowledge that M3 mounts offer benefits beyond the mitigation of rear bounce. I may later install them to reap those benefits.

I agree with you. Before adding the Bilsteins, the car felt like a disaster. It almost felt as if the rear subframe bushings had completely failed given how much sway the rear of the car would exhibit. After Bilsteins and the Dinan rear kit, that sensation is almost completely gone. I'm sure the shocks themselves account for 99% of that, but either way, I'm with you; adding inserts or swapping the rear subframe bushings was a priority in the past. Now I'm not even worried about it.

[DrRobert]

I see Dinan offers this part in both 10mm and 12mm size:

10 mm

12 mm

My car is listed for both parts. How do you know which one to get?

[thakid22]

Originally Posted by FCobra94

I agree with you. Before adding the Bilsteins, the car felt like a disaster. It almost felt as if the rear subframe bushings had completely failed given how much sway the rear of the car would exhibit. After Bilsteins and the Dinan rear kit, that sensation is almost completely gone. I'm sure the shocks themselves account for 99% of that, but either way, I'm with you; adding inserts or swapping the rear subframe bushings was a priority in the past. Now I'm not even worried about it.

Exactly! Your (and my) sentiments have been echoed by every person who I have come across with the Dinan kit. The only people that don't seem to believe in the Dinans are those who don't have them.

[thakid22]

Originally Posted by DrRobert

I see Dinan offers this part in both 10mm and 12mm size:

10 mm

12 mm

My car is listed for both parts. How do you know which one to get?

10 mm are for cars with non adjustable shocks.

The 12mm kit is for cars the have adjustment knobs on top of the shocks, ie. cars with adjustable shocks.

[ajsalida]

OP glad you fixed your bounce.

Curious that BMW uses the same rear upper shock mounts as e9x cars on M3's. Also that no legit race shops sell upgraded rear upper shock mounts for e9x, at least not Turner, TC Kline, VAC, etc. When they do sell them for other chassis (e36, e46 etc.), and also upgraded bushings for nearly every other rubber piece in the rear of the e9x cars.

[chris82]

I had this mod done when my JRZs were installed; only I got the powerflex black mounts. Very happy with them

[ajsalida]

Originally Posted by Chrisar82

I had this mod done when my JRZs were installed; only I got the powerflex black mounts. Very happy with them

Interesting...Where did you get those?

edit:

http://www.ecstuning.com/BMW-E90-335...ies/ES2650605/

[mlifxs]

I did these recently with a spring / shock change. Things definitely feel better out back but too many changes to give credit to the mounts.

Only 14 more years until I get my Dinan badge

[GreekboyD]

How much NVH is added with these? I'm already on coils so I'm assuming these would be a PITA to install?

[DrRobert]

I wonder if we're all talking about the same rear "bounce" phenomenon here. At the beginning of this thread OP was asked:

Just to confirm youre talking about the mid-corner hit a bump feeling?

and replied:

Yes. This eliminates the pogo action you get at the rear when you hit bumps while cornering.

My E90 335i has at least 2 different types of unwanted rear motion:

Bounce #1: When hitting a bump while driving hard through a turn the rear end jiggles sideways, which is quite unnerving. For me that is "the mid-corner hit a bump feeling", which I believe has been attributed to the subframe bushings.

Bounce #2: When hitting a bump while driving straight the rear end bounces up and down more than I want it to, which is more of an annoyance. This is what I would describe as "pogo action".

OP, was your rear end bounce more up and down or side to side instability?

I just got my car back yesterday from having M3 subframe bushings installed (as well as front control arms and rear guide rods ). I've only been driving it one day, but my initial impression is that Bounce #1 is greatly improved, but that Bounce #2 is still there, i.e. it still pogos over bumps with the stock shock mounts. I don't know if itt is caused by the BMW shock mounts or the Koni FSDs (I'm not going to ask CVC because he told me not to get them!) or something else entirely, but the up and down rear bouncing is not caused by the subframe bushings IME.

[thakid22]

Originally Posted by DrRobert

I wonder if we're all talking about the same rear "bounce" phenomenon here. At the beginning of this thread OP was asked:



and replied:



IME, my E90 335i has at least 2 different types of unwanted rear motion:

Bounce #1: When hitting a bump while driving hard through a turn the rear end jiggles sideways, which is quite unnerving. For me that is "the mid-corner hit a bump feeling", which I believe has been attributed to the subframe bushings.
Bounce #2: When hitting a bump while driving straight the rear end bounces up and down more than I want it to, which is more of an annoyance. This is what I would describe as "pogo action".

OP, was your rear end bounce more up and down or side to side instability?

I just got my car back yesterday from having M3 subframe bushings installed (as well as front control arms and rear guide rods ). I've only been driving it one day, but my initial impression is that Bounce #1 is greatly improved, but that Bounce #2 is still there, i.e. it still pogos over bumps with the stock shock mounts. I don't know if that is caused by the BMW shock mounts or the Koni FSDs (I'm not going to ask CVC because he told me not to get them!) or something else entirely, but I still have some work to do to stabilize the rear. Gettin' there though!

Bounce #1: The lateral movement of the rear end. It makes the rear feel skittish over bumps with cornering and power. I only experienced this when my rear tires were worn, or my alignment was bad. I don't fault the car for this.

Bounce #2: The back end bouncing up and down(vertically, like someone jumping on the trunk) over bumps, surfaces, and imperfections... I have experienced this to some degree in EVERY E9x I've driven (never drove M3, though). I fault BMW design for this.

The Dinans help fix Bounce #2. If bounce #2 irks you. Do yourself a favor and buy the Dinans ASAP. You will be pleased.

Tire pressure, Shock Valving, Strut Mounts, Subframe Bushings etc. all effect the rear bounce.

FSD's bounced more at the rear anyway (on some surfaces). I did not llike this and got Bilsteins to replace them.

[ajsalida]

It's almost like rear subframe bushings and shock mount problems have nothing to do with each other....

[cdgatti]

The most likely explanation here is the Bilstein HD shocks, I also replaced my stock rears with the HD shocks (and new oem rsm) and the rubbery bouncy feeling was extremely diminished. The dinan rsm are intended to regain some rear travel before engaging the secondary springs (bump stops) ON lowered cars. They are almost useless* on a car with HD shocks as that car will even sit a little higher than stock.

* useless if the oem rsm were in reasonable shape and installed properly.