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      12-12-2017, 07:56 PM   #1
spazzyfry123
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Bushings

Car background:
2011 E90 M3 6MT base with OEM suspension (non EDC/ZCP) with about 60k miles on it.
After keeping it in the garage, I've realized that it's much more fun to grab these keys instead of the DD. So I sold the other car and made this my DD, and going into maintenance/upgrade mode to make the car a bit more reliable and solid. Rod bearings will hopefully be done by year's end, new spherical bearing shifter is being made...But a gripe of mine as I drive it more is the car feels a little...loose.

I have another thread that I think I should consolidate with this one and is better suited for this forum regarding a clunk I am experiencing if my shifts are not perfectly aligned (6MT) http://www.m3post.com/forums/showthread.php?t=1442238

I'm a bit sensitive to mechanical feeling in the car in the sense that I seem to always throw small "issues" out of proportion, but also sensitive in that I love the mechanical feedback from the car. The clunk I mention above may just be normal, but I'm not convinced. I am also noticing that when I let off the gas while driving that the car's behavior does not appear very solid. I won't say the car darts, but it seems to have a higher reaction to on/off throttle than I would expect. It certainly shifts around - drivetrain movements alter the car's balance. Again, I'm pretty sensitive to it and it's making me paranoid.

Now I'm sure that a lot of this could just be usual stuff, but what's a good recipe and things to generally go after to tighten the car up? It is a daily driver, but one with decently loud exhaust that will mask drivetrain whine and the lot. I want a solid car with plenty of feedback but not a go-kart on cinder-blocks when I go over a bump.

From what I've been finding, solid rear subframe mounts with upgraded Delrin-type differential bushings seem to be the go-to. I'd like to get your input on my specific scenario. Should motor mounts be addressed? What about control arms? Etc...

I should also mention that I am considering lowering the car, but I think a full KW V3 coilover setup or similar would be overkill on a car that sees road miles mainly with the occasional trip to the mountains and an AutoX weekend. I'd like to be planning ahead with what is done to the car so that I don't go back and change things around again when I come back to lowering the car. A system I was considering is KW's kit here since I'm pretty impressed with the OEM suspension https://www.kwsuspensions.net/produc..._/-/-/25320057

Long-winded, I know. What's everyone's take?

Thanks!
Tyler
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      12-12-2017, 08:17 PM   #2
pbonsalb
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Definitely do stiffer rear subframe bushings. Makes an immediately noticeable difference. Beware solid or Delfina or 75D poly diff bushings ó they will whine. My 95A poly diff bushings whine about as much as I would tolerate in a comfortable daily driver.
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      12-12-2017, 08:30 PM   #3
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Originally Posted by pbonsalb View Post
Definitely do stiffer rear subframe bushings. Makes an immediately noticeable difference. Beware solid or Delfina or 75D poly diff bushings — they will whine. My 95A poly diff bushings whine about as much as I would tolerate in a comfortable daily driver.
Thanks. Rear (and differential) seems to be the only one that I ever see mentioned. Are there other things that are generally changed/upgraded while this is happening? Would you recommend solid subframe bushings for the every day ride?

I really think I'll be focusing my "mods" on suspension and chassis bits over power. Car is pretty balanced, but I just wish it was a little tighter.
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      12-12-2017, 09:46 PM   #4
pbonsalb
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I donít think solid subframe bushings add much nvh. I used 75D poly mostly because they are a piece of cake to install. 75D is close to delrin. Itís the diff bushings that will whine if too hard.

I would check your suspension and replace any arms with worn bushings. The only ones I might upgrade for a street car are the front tension or strut rod bushings. Some people run slightly stiffer motor mounts ó I tried Rogue but they added too much nvh at idle so I sold them. I would at least replace them with new Corteco mounts since they seem to be worn on most cars when changed - sometimes cracked and usually a little bit collapsed.
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      Yesterday, 09:00 PM   #5
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So talking with my shop today they will change out the motor and transmission bushings/mounts at cost with no added labor when they dig in to change out my rod bearings. I think this is a good start since I've read that our motor mounts tend to fail prematurely. Seeing that I'm just buying parts and no added labor, let's do it. What recommendations do you folks have for a street car that will see some fun time now and again? While I've never used it, AKG has been recommended to me in the past.

Motor: (75d too hard? I was only able to find these in this hardness)
https://www.akgmotorsport.com/produc...yurethane-75d/
Transmission: (I'd imagine the transmission and motor mounts should match; but I only see 95a on their site)
https://www.akgmotorsport.com/produc...ly-95a-e9x-m3/

As a separate question, seeing that quite a bit (labor) is involved to change the rear subframe bushings over to solid, what other items are generally good to get done while you're in there? Would now be a good time for a different sway bar for example?
I'm going to replace the differential bushings as well as change its fluid/seals. Other (very helpful) threads on a similar subject recommend aluminum subframe and Delrin differential - agree?

Subframe: (Solid aluminum)
https://www.turnermotorsport.com/p-4...e82-1m-e9x-m3/
Differential: (95a a good choice? Or will I need to replace these "frequently"?)
https://www.akgmotorsport.com/produc...yurethane-95a/

I'm a big believer in making the most of time while you're in there. I'd like for whatever approach I take for it to be as much of a "do it and forget it" type deal so that I'm not replacing bushings every 30k miles. This is why my '71 Honda CB is 100% completely disassembled in the garage when all I wanted to do was change out the ignition system...

Last edited by spazzyfry123; Yesterday at 09:41 PM.
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      Yesterday, 11:08 PM   #6
pbonsalb
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If itís a street car, I think if you put in 75D motor mounts and 95 trans mounts you will be paying for labor to take them out pretty soon and parts and labor to install softer mounts in those locations.
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      Today, 08:23 PM   #7
spazzyfry123
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Quote:
Originally Posted by pbonsalb View Post
If itís a street car, I think if you put in 75D motor mounts and 95 trans mounts you will be paying for labor to take them out pretty soon and parts and labor to install softer mounts in those locations.
As you can tell, this is new for me. Is the best solution to change out to OEM? I've seen the "Group N" style as well, but don't really understand why one way or another.
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      Today, 09:54 PM   #8
pbonsalb
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For street motor mounts, I would do OEM, which is made by Corteco, or maybe Bimmerworld Group N replica or maybe Vibra Technic Street mounts. I would want to ask someone about the Bimmerworld mounts before buying them. People say the Vibra Technic Street mounts are fine. I went with Corteco after trying Rogue and finding they added too much NVH.

Trans mounts donít seem to wear like motor mounts. I changed my motor mounts at 60k and they were slightly collapsed ó a little shorter than new ones. My trans mounts at 90k felt just like new ones. And new ones are very soft. I am about to try 80A trans mounts ó Iíll install them this weekend. I think they may be too stiff but I decided to give them a try. Iíll know more in a few days.
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