Poll: Did Polyurethane Rear Subframe Bushings Prevent Diff Mount Failure?

[ticklemejoviemo]

i'll be installing Vorshlag camber/caster plates so likely will want to get centered bushings correct? also, the car is an occasional daily driver/track vehicle so I dont need to go all out race spec with everything. I know AKG haa the two different versions and IE makes some http://www.iemotorsport.com/bmw/E30-...bshRUBBER.html which I'm unsure if they use a different rubber compound than factory.

It seems people have been satisfied with IE green RSB's, so was curious if everyone leans towards a particular FCAB, but I do understand the preference of the different types

[Blacklane]

Let's start a new thread on FCABs. You'll get better responses.

[MTRD3]

i know this is a RSB thread, But I'm curious as to what people are using (with good results) for FCAB's? I currently have IE RSB's & RTAB's. Am in process of installing TCK DA's. Thanks for any help!

p.s. i did try searching but couldn't find anything useful

I've got Powerflex Purple FCAB's and am very happy with them. Didn't experience any real increase in noise, vibration or harshness either after installing them. I'd recommend them and do it again if I got another coupe.

It depends on your objectives. There are so many choices that this question deserves to be another thread. I would ask the members how they chose their FCABs and how it turned out.

Let's start a new thread on FCABs. You'll get better responses.

Good point and idea.. will be much more helpful to the next person who searches titles for such a topic.

[ticklemejoviemo]

new FCAB topic started: http://forums.bimmerforums.com/forum....php?t=2098559

[Deano1712]

Being argumentative isn't in my nature__I much prefer to avoid conflict, than to incite it__BUT, I have seen examples tainly none that'd completely seen (and repaired/reinforced) cars with trunkfloor failure and zero damage to the differential mounting bracket....

Seems that you are agreeing with me, and adding the bracket failure as second mode (which is obviously valid). Do you agree with the 550kg load figure, or have a different assessment? The load applies to both modes so is key.

[jbrannon7]

I have put in the poly diff bushing. I have one crack that started years ago but I drilled it and it has not gotten worse. I think the best thing that I did to prevent the failure was to replace the 85lb battery with a 17lb battery. That battery is suspended directly over the diff and my crack is at the corner of the battery cutout directly over the diff hanger.

joe

[fmcfad01]

Maybe Randy can comment directly on what he saw in my trunk floor that he just repaired. He mentioned that he had never seen the spot welds that were popped on my car be the only popped spot welds.

That said, I went down to his place for rod bearings and left with a reinforced trunk floor. I honestly didn't think my car had any issues. He cleaned the dirt off the underside of my car and found 2. He scraped the asphalt mat off my trunk floor and found several more. He also found the seam on the drivers side starting to separate. My diff ear was fine...no cracking. I've had Poly Bushings in my car since ~30k miles.

I guess what I'm trying to say is, many of us may think our trunk floors are fine when in reality they are very hard to check without really getting your hands dirty. A cursory glance isn't going to show you anything unless you've got major problems.

And this is all coming from a guy who was pretty negative on sub frame reinforcement and doesn't view it as preventative maintenance. I had it done on my '99 and swore I wouldn't have it done on my 01 unless there was evidence that it was needed.

The fact of the matter is, there were some initial signs of things starting to happen to my trunk floor and my car was at Randy's house. I think my exact words to him were something like, we'll, if I want the artist to do an original work, I might as well have it done. So he did it for me.

[Wojtek79]

I have put in the poly diff bushing. I have one crack that started years ago but I drilled it and it has not gotten worse. I think the best thing that I did to prevent the failure was to replace the 85lb battery with a 17lb battery. That battery is suspended directly over the diff and my crack is at the corner of the battery cutout directly over the diff hanger.

joe

What battery did you put in?

[jbrannon7]

One of the small Odyssey batteries, the PC680 as I recall.

[jbrannon7]

Here are some old and current photos of my trunk floor. The old photos are from Oct 2008. You can see a crack near the battery cutout and a crack around a stitch weld. I drilled the crack near that battery that day with a 1/8 drill bit. Some thing I was taught in high school metal shop. The current photos are from today. You can see the crack that I drilled has not progressed. You can see the stitch weld crack may have gotten very slightly worse. You can see one pulled spot weld that I don't have a 2008 photo of so that probably occurred sometime since then. I have put around 600 minimum and probably 800 autocross runs on the car in the last 6 years. I compete and push the car hard but I never dump the clutch, well maybe a few time from 1st to 2nd but never off the line.

Also is a photo of the battery I installed 6 years ago. I have had to replace it a couple times. It does fine until it sits thru a cold winter. I now live in Florida and it should last longer here.

First 3 photos are from 2008, rest are from today.

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Can only do 5 photos so another post will follow.

Joe

[jbrannon7]

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[m3mods]

Does this pertain to standard E36 m's or is this mostly relevant to m coupes, roadsters, z3's etc? The reason I ask is that 99% of the posts in the thread are from owners of the aforementioned cars, not e36 m's. I'm about to throw some polyurethane at my subframe and surrounding areas and this is the first I've seen about keeping certain pieces oem rubber.

[mcoupemindy]

Does this pertain to standard E36 m's or is this mostly relevant to m coupes, roadsters, z3's etc? The reason I ask is that 99% of the posts in the thread are from owners of the aforementioned cars, not e36 m's. I'm about to throw some polyurethane at my subframe and surrounding areas and this is the first I've seen about keeping certain pieces oem rubber.

E36s are subject to a different kind of subframe failure. The way the differential attaches doesn't hang from the trunk floor on the E36. This thread pertains to the Z3 chassis cars.

[m3mods]

E36s are subject to a different kind of subframe failure. The way the differential attaches doesn't hang from the trunk floor on the E36. This thread pertains to the Z3 chassis cars.

Ah ok thanks. That's what I thought but seemed worth it to ask. With rtab pocket, rear sway bar and rear subframe mount (all 4) reinforcements is it recommended to run all poly bushings or is there a benefit to having rubber in some locations? I'll probably be doing oem rubber with limiters in the rtabs pockets just cause they should last longer and seem to be on par with poly performance wise anyway. Everything else (subframe & diff) I was going to replace with poly unless there is some reason this may increase some form of failure.

[BimmerBreaker]

Ah ok thanks. That's what I thought but seemed worth it to ask. With rtab pocket, rear sway bar and rear subframe mount (all 4) reinforcements is it recommended to run all poly bushings or is there a benefit to having rubber in some locations? I'll probably be doing oem rubber with limiters in the rtabs pockets just cause they should last longer and seem to be on par with poly performance wise anyway. Everything else (subframe & diff) I was going to replace with poly unless there is some reason this may increase some form of failure.

You'll be better off asking that question in the E36 subforum. But there are some very knowledgable people here so maybe someone can help you... but you are asking about an E36 in the Z3 section. Our cars are similar but the rear suspensions/subframes are very different. Z3's run an E30 rearend.

What is good for our cars may not be good for yours.

[m3mods]

You'll be better off asking that question in the E36 subforum. But there are some very knowledgable people here so maybe someone can help you... but you are asking about an E36 in the Z3 section. Our cars are similar but the rear suspensions/subframes are very different. Z3's run an E30 rearend.

What is good for our cars may not be good for yours.

Haha yeah I know. I was mostly hoping to catch Jonathan or Mr Forbes attention since they are both in the thread and quite knowledgeable.

[BimmerBreaker]

Haha yeah I know. I was mostly hoping to catch Jonathan or Mr Forbes attention since they are both in the thread and quite knowledgeable.

Your telling me you dont trust the insight of a bunch of teenagers who think their 95 M3 is faster than a Veyron?

[m3mods]

Your telling me you dont trust the insight of a bunch of teenagers who think their 95 M3 is faster than a Veyron?

[mcoupemindy]

Ah ok thanks. That's what I thought but seemed worth it to ask. With rtab pocket, rear sway bar and rear subframe mount (all 4) reinforcements is it recommended to run all poly bushings or is there a benefit to having rubber in some locations? I'll probably be doing oem rubber with limiters in the rtabs pockets just cause they should last longer and seem to be on par with poly performance wise anyway. Everything else (subframe & diff) I was going to replace with poly unless there is some reason this may increase some form of failure.

Sorry, just saw this! Anyhow, it seems like the best recipe for the E36 is poly subframe bushings and hard poly in the three differential locations.

The e36 chassis is a bit different but does occur with worn bushings. I believe that Turner sells the plates and they weld into the chassis. I've seen a few cars on my lift that had this reinforcement done.

[m3mods]

Sorry, just saw this! Anyhow, it seems like the best recipe for the E36 is poly subframe bushings and hard poly in the three differential locations.

The e36 chassis is a bit different but does occur with worn bushings. I believe that Turner sells the plates and they weld into the chassis. I've seen a few cars on my lift that had this reinforcement done.

Awesome thank you for the reassurance.

[rotorhed]

IE RSB Remvd 11-2018.JPG
FWIW: IE RSB's installed back in March 2006, now have ~33,000 miles on them and still are in great condition and pliable.

[Trademark1]

I saw some recent threads reviving the perennially popular subframe bushing topic - which made me recall this thread.

The last update to the non-scientific poll was 2014 - and not a big sample size - almost all of it courtesy Mr. Forbes.

I understand the theory of the poly bushings but I am curious about the data. Particularly as my trusted independent mechanic swears (who sees way more of these than I would) the problem is over-blown (although he admits e36 sedan is a real issue) - and that poly bushings have detrimental effect on character of car. I do think that looking through web forums can distort the data in the same way that if one hangs out outside of a hospital you get the impression that a whole lot of people are sick. People with no separation problems likely don’t post about it much. That said, when I was shopping for Z3’s, I would say about 1/4 of the vehicles I looked at (in the 30-80K mile range) had one or more popped spot welds. I didn’t get underneath all of them, but I doubt the entire other 75% had poly bushings.

I would be curious to update the straw poll. Are those w/ poly bushings installed (and no RF kit) still trunk separation symptom free? How many miles/years later? For those w/ original or replacement rubber bushings - what result? I have a 2000 S52 with about 55K miles on presumably original rubber (in need of replacement I would think) - but no visible trunk/diff mount issues. Not sure of how prior drivers cared for vehicle - but presumably street-driven only.

[s8ilver]

2.8 Coupe, poly installed eons ago. 163k miles, still no popped welds. Conversely, my non-poly (at the time) M Roadster popped two welds at 52k miles, but was supercharged at 47k. Poly and RF kit installed at the time, so of course no issues since.

[zellamay]

I wonder what that indy mechanic meant by "detrimental effect on the character of the car", since I, and others, have noticed a serious improvement to the car from installing poly. Did he actually drive the cars for any length of time? ..... I would say that 1/4 of the cars popping welds makes it a serious problem, worthy of attention by every owner. ..... One more stat: I have over 25k, in 5 years, on my 98 M Roadster poly bushings. No signs of popped welds.

[ProductUser]

It's been 6 years and 15k miles since my poly\RF install (no rivets to worry about ). No issues noted.