Polyurethane Bushings

[lukeADE335i]

I have Poly rear subframe mounts, trans mounts, offset CABs and adjustable strut tops - in a DD, there is definitely increased NVH. Generally I can live with it, but it does get a bit tiresome every day. Sometimes I wish I'd stuck with rubber, although the handling is great on a twisty road.

I am running Whiteline bushes in "street" hardness, not "race", although at some point I may just return my strut tops & trans mounts to stock to see whether this helps.

[Ray Smoodiver]

I'm running Powerflex Subframe, trailing arm bushes and offset front CAB bushes, with Ireland Engineering engine mounts, there is absolutely no increase in NVH.

I'll be going with the powerflex diff and f/r ARB bushes over winter (downunder land) and don't expect to have much more of an NVH issue.

As has been mentioned, biggest culprit of NVH is strut towers and trans mounts.

[JGood]

Ha, fair enough, alot of it depends on use I think. On the cars that have been tracked at all the rubber is pretty gummy. The ones I pulled out of my 2002 (same as E30) were entertaining.

Makes sense. I have read that the harder poly bushings can cause excessive binding in the trailing arm, do you have any input on that? I believed it to be true after moving my trailing arm up and down without a spring installed. Lots of noise/resistance. But, it is just a bushing, not a bearing...

[SkiFree]

Poly TAB's must literally last forever then, because my factory TAB's were still decent after 28 years/295k miles. Haha

Ha, fair enough, alot of it depends on use I think. On the cars that have been tracked at all the rubber is pretty gummy. The ones I pulled out of my 2002 (same as E30) were entertaining.

[JGood]

Disagree with your "theory" on the trailing arm bushings. The rubber wears quite a bit faster than the urethane, have proven that a number of times.

However, yes the trans mount seems to be the largest culprit for added NVH. The E21 mounts are a great way to go.

Poly TAB's must literally last forever then, because my factory TAB's were still decent after 28 years/295k miles. Haha

[e30sky]

So guys i am glad you all took the time to help me out on this. i had in mind the same urethane bushings but as i said before the urethane that i want to use would not be the hardest. i will be using the ones they classify as "Street" not "Race". i was thinking the urethane all around with stock trans and engine mounts. I am glad that Jgood shared his set up and explained it for me to get an idea. About the control arm bushings, i will be sticking to the centered set up but will be urethane.

This brings me to my last and final question......since it will be urethane ( STREET compound ) would i still need to do any sort of reinforcement as compared to solid bushings which need certain things to be reinforced?

[SkiFree]

Trailing arm bushings - OEM Lemforder. The OEM bushings are extremely hard rubber, probably almost as hard as poly. They are cheap, pretty easy to install, will last probably 200k-300k miles. e30 trailing arm bushings sort of bind by design, since the arc of the trailing arm isn't perfectly straight, so putting a super hard poly or UHMW in will create some resistance when the trailing arm moves through it's arc. Not ideal IMO, could potentially wear them quicker.


Trans - I'd go stock or e21, with the aluminum cups if you need stiffer. Trans mounts can add some serious NVH. I went from stock to e21 mounts with cups, and it added a noticable amount of NVH. I tried UHMW mounts at one point back when I had my m50, I took them out after 10 minutes. The car was so loud, my friend in the passenger seat had to yell for me to hear him. It was insane. I also had UHMW engine mounts at the time, which weren't terrible, but then when I put those trans mounts in, the car was just unbearable.

Disagree with your "theory" on the trailing arm bushings. The rubber wears quite a bit faster than the urethane, have proven that a number of times.

However, yes the trans mount seems to be the largest culprit for added NVH. The E21 mounts are a great way to go.

[Roysneon]

I'll echo Jgood on the trans mounts. I love my delrin engine mounts but had to take out the trans mounts.

[JGood]

Here is my setup, and why I chose what I did.

Subframe bushings - AKG poly. Very easy to install, affordable, much easier to replace then rubber bushings. Also these don't really add significant NVH, unless you go UHMW/solid/etc... Should last a very long time.

Trailing arm bushings - OEM Lemforder. The OEM bushings are extremely hard rubber, probably almost as hard as poly. They are cheap, pretty easy to install, will last probably 200k-300k miles. e30 trailing arm bushings sort of bind by design, since the arc of the trailing arm isn't perfectly straight, so putting a super hard poly or UHMW in will create some resistance when the trailing arm moves through it's arc. Not ideal IMO, could potentially wear them quicker.

Rear diff bushing - OEM. I can't imagine anything but a high powered race car needing an upgraded diff bushing.

Front CAB. I installed OEM e30 M3 offset bushings. The offset is useless IMO. I don't notice a difference. Didn't notice a difference in my track car either. All it did for me was push the wheel forward, which is annoying. I'd say get OEM e36 M3 centered bushings.

Engine mounts- I'm using revshift m60 mounts. That's because I have an m60. They work great. So do factory m60 mounts. But I need my engine to stay 100% exactly where it's at, because I have like 3mm of clearance in every direction in my engine bay.

Upper strut mounts - Unless you need camber adjustment, I'd go OEM. Camber plates are expensive and can be a PITA as far as NVH and maintenance.

Trans - I'd go stock or e21, with the aluminum cups if you need stiffer. Trans mounts can add some serious NVH. I went from stock to e21 mounts with cups, and it added a noticable amount of NVH. I tried UHMW mounts at one point back when I had my m50, I took them out after 10 minutes. The car was so loud, my friend in the passenger seat had to yell for me to hear him. It was insane. I also had UHMW engine mounts at the time, which weren't terrible, but then when I put those trans mounts in, the car was just unbearable.

[SkiFree]

Personally I say urethane suspension but rubber trans/diff/engine mounts.

BUT... and I quote myself

Frankly, you're going to get a lot of opinions, none o which should be considered "wrong" or "right". You need to be aware of the harshness ratings of different urethane and what you think you can tolerate.

[e30sky]

hmmmmm......now i am in a spot lol. so stock rubber bushings u say?

[mulletman]

stock bushings rite? the thing with that is that i'd have to keep buying them more often as they would wear faster and i cant just pick them up here in Guyana country easily. so i was thinking the urethane one since they wear less, i think

I just did bushings on my car. It had been 24 years and 130k miles since new. They were in okay shape. Rubber bushings will last quite a while.

[e30sky]

stock bushings rite? the thing with that is that i'd have to keep buying them more often as they would wear faster and i cant just pick them up here in Guyana country easily. so i was thinking the urethane one since they wear less, i think

[mulletman]

Just do new rubber bushings. Cheap, and handles just fine.

[Smelser]

Wat.

No.

Don't do that.

Subframe reinforcement plates on the motor mount tabs aren't a bad idea, but I have delrin mounts and stock subframe, it hasn't broken yet.

keep in mind, I never get my car out of second gear. I hit the rev limiter, but second is it. high speed stability is not something I am concerned about. making the car "dartier" and more responsive to my input is better. if it oversteers I can correct that with more or less wedge (cant remember wich way to go to tighten or loosen the car at the moment)

my subfram is fine, but the revshift mounts ripped the bolt head right out of the plastic. wound up drilling them out and using a grade 8 bolt straight through the plastic (poly stuff) it has held so nice that we left it.
had stock rubber trans mounts till "the wedding incident" that jarred the car so hard it ripped them clear apart (3 months after the motor mounts ripped)
ended up building a new trans crossmember with a GM trans mount and more steel fabbed to fit the tranny. quicker and easier to replace in a pinch if we need to.