Poly bushings

[Alaska Ted]

Hey guys,

All of the bushings in my son's 89 ix need to be replaced and we were thinking about using soft 80a poly bushings. The car has not been lowered and will be staying that way. We're looking for some advice on which brand you are using and would recommend. Does anyone make a ix poly subframe bushing? I've read a bit about using rwd sub frame bushings and shimming, but I don't quite get it. I've also heard that poly diff bushings are not the way to go, but never got an explanation on why. Any info on poly bushings good or bad would be appreciated.

Thanks,
Ted

[Kershaw]

If you're going with soft poly, why not stick to oem rubber for all of the bushings? It lasted 30 years up until now, it's very durable.

I can understand going with a much harder poly for race reasons, but why soft? And poly has a tendency to disintegrate after 5-7 years.

[Alaska Ted]

Poly bushings

I was under the impression that soft poly was an improvement in handling, and durability. If thats not the case, I'm all in for OEM. Thanks for the reply.

Ted

[tk32]

Don't believe everything you read on the internet especially from a noobie, but:

I have just spent a load of time researching this exact topic and ordering parts. It should be noted that my car is on H&R sport springs now and I will be upgrading to Koni adjustable and Ground Control coil over conversion (custom spring rate Eibach) springs soon, this car is a spirited DD when its operational.

2 thoughts: I do not believe anyone makes poly rear subframe bushings for iX, yes different (just like everything else). I also do not believe anyone makes poly rear diff bushing for the iX. See above.

If everything needs replacing those are two expensive oem parts right there, compared with oem RWD (interchangeable if one does both? I would like to hear opinions on this)

1 reason to upgrade to "soft" polyurethane: price point. It is cheaper than oem BMW parts. If you look at durometer the street poly is typically 80A, on the upper range of rubber things

As far as durability, I cannot say. But I'll let you know in 30 years. :drink:

tk

[Alaska Ted]

Wow, thanks for the input. Did you end up ordering poly? If so, what hardness and what brand? I've used soft power flex bushings on an e36 and was very happy with the result. Please keep the info/opinions coming.


Ted



BTW I'm not an advanced member. My kid figured out how to change my signature. It should read SUPERNOOB. Moderators feel free to change that. Dang kids!

[tk32]

I have found good service at Ireland Engineering (a lot of the polyurethane, and I talked for 20 minutes with a tech today. It's the best when a sales guy puts me on hold and a tech picks up). And Pelican Parts seems to have a secret for getting obscure oem parts which many times needed to be tracked down by part number only, I realized. Certainly other locations can do the same.

Note that I have found very few non-iX specific part numbers in this endeavor. Not to say rwd or other replacement is completely out of the question, but suspension/driveline can be a tricky situation and I might do it all wrong (but my brother has a rwd e30 and I will sell him all the parts, or buy one to swap 'em into or,). Those German Engineers went haywire on suspension

I have no good answer, only research and my gut investment of some rwd parts. It all makes sense in my mind.. :crazy:

tk

[Kershaw]

As far as durability, I cannot say. But I'll let you know in 30 years.

I've seen 5 year old poly engine mounts, never used, just sat, crumble upon installation. Maybe that specific example came from a bad batch of poly. Another consideration is squeaking. Poly squeaks and it needs to be lubricated every few thousand miles.


It is cheaper, so that's a consideration.

BTW I'm not an advanced member. My kid figured out how to change my signature. It should read SUPERNOOB. Moderators feel free to change that. Dang kids!

It's based on your post count, your kid didn't change it. Once you went over 100 posts or something.

[Nisse Järnet]

Ive been using delrin subframe and diff bushings on my rwd E30 since 2007 and they are still just fine! Same with engine mounts, but i replaced those in 2011 because new engine and new bushing height. Never touched them :)

Never used poly though.

I think i have seen IX specific poly or delrin mounts but i dont remember where...

[The Dark Side of Will]

I've seen 5 year old poly engine mounts, never used, just sat, crumble upon installation.

The way that the BMW community makes urethane engine mounts is an engineering disaster. The design is the worst possible thing to do with the material properties of urethane. It literally could not be any worse.

Never used poly though.

Well don't... it's actually a really horrible material for any bushing or mount on a car. It's only used because it's cheap, easy and requires minimal capital/tooling investment.

[tk32]

Many informative things here as well: (also where I borrowed that cool chart from)

http://www.r3vlimited.com/board/showthread.php?t=224221

I am going for IE poly rear subframe and trailing arms with oem or oem+ driveline, engine and trans mounts. Not oem iX rear subframe bushings will change my geometry (shorter), but since I am on H&R springs for now its not a bad thing, I think. oem suspension may require all oem bushings, IMO

MZ3 diff bushing and E21 trans mounts :up:

tk

[Alaska Ted]

Good stuff. Thanks

[Kershaw]

The way that the BMW community makes urethane engine mounts is an engineering disaster. The design is the worst possible thing to do with the material properties of urethane. It literally could not be any worse.

What would you do to change it?

[Northern]

Not oem iX rear subframe bushings will change my geometry (shorter)

Not at all, the subframe stopper washer/spacer dictates that. The only issue you'll encounter with aftermarket bushings is that the inner bushing sleeves will be too short, so you'll need to make a spacer or new sleeve. Pics here:

http://www.bimmerforums.com/forum/showthread.php?1922553-iX-Subframe-Mount-Question

[The Dark Side of Will]

What would you do to change it?

*Good* urethane mounts have interlocking steel parts inside so that when the urethane fails the mount can't come apart. Also, because of the interlocking internal components, the urethane is under compression when the mount is under tension. This is *MUCH* better for urethane as it's a lousy material for tension.

However, urethane itself is more "springy" than rubber... it's more on the elastic side of visco-elastic. This means it stores more energy and can contribute to clutch chatter and wheel hop.

Here's an example of a well designed urethane mount: http://www.summitracing.com/parts/ens-4-1104g

My first suggestion is actually to use OE BMW mounts... E39 M5 or E38 750i mounts are made for a good bit of torque and are pretty tough.

If there's too little clearance from the engine to something next to it and those mounts allow enough motion to contact, then look into something else.

Ferrari did a very good job with the engine mounts for their 308's. They were concerned about NVH problems because the flat crank V8's vibrated a lot more than their V12's. They built a high end machinery mount... it has it all: rubber to absorb the vibration, spring to carry the weight, mechanically captive, rebuildable...

[tk32]

Not at all, the subframe stopper washer/spacer dictates that. The only issue you'll encounter with aftermarket bushings is that the inner bushing sleeves will be too short, so you'll need to make a spacer or new sleeve. Pics here:

http://www.bimmerforums.com/forum/sh...Mount-Question

Cool! Thanks. If I am reading this correctly, which I like to think that I am...
(also thanks to the OP for the thread direction)

i subframe bushings going into a lower then stock iX: will also require i stopper washers? In addition to using an i diff bushing and spacers to compensate driveline geometry?


Going to need more monies, and beers :drink: