Suspension Overhaul Excel Sheets

[Singing6]

Ladies and Gentlemen,

I present to you a collection of a few years of my trials and tribulations all in two Google sheets. Most of what I say here will be a repeat of what is said in the disclaimers at the start of each file, but I will say it anyway. These sheets do not include anything regarding the springs and struts. That is because that is far too personal of an opinion. The information in these is free of any sponsorships or promotions. I chose these retailers for parts based on pricing and customer service. I am receiving no payment for this information, and it is yours to do with as you please. But understand that there is a reason behind every single part on each list. Also, this list is most relevant to US members in terms of the retailers. But if you are abroad, feel free to substitute your own supplier, just pay attention to the brand I specify for each part, as again, there is a reason, likely one learned the hard way. So without further ado:

Here is the list for the front suspension:
https://docs.google.com/spreadsheets...it?usp=sharing

Here is the list for the rear suspension:
https://docs.google.com/spreadsheets...it?usp=sharing

Again, these are for the betterment of all of you, if you find errors, please let me know here in this thread, Im always looking for ways to further improve the E34 chassis!

Thanks,
Singing6

[sugaki]

Curious why you think a straight strut bar is better than the others--unless the strut bar is poorly designed and has the rigidity of a wet noodle, it should transfer the horizontal/vert force to the opposing tower even if it's arched. I'd think hinged would have a bigger impact than arched.

[Singing6]

It is a logical question, and I only came to this realization after taking some of my early engineering classes. I know Wikipedia is terrible for understanding mathematical or engineering principals, because it cant simplify, but here is an intro:

https://en.wikipedia.org/wiki/Buckling

Once that bar has any bend in it, it will simply deform more in the direction of the bend rather than bearing the load. Don't get me wrong, it will still transfer some load across, but with all the different bars being between 100-300 USD, Im going to pick one that is actually structurally sound. Reducing the angle of the bends will lead to it feeling stiffer, but is never as good as a straight bar. Having a hinge does change how easily the bar will start to buckle, but the root issue is still buckling. Some E34's may not currently have ANY structurally sound options on the market. I know the S38 is one that is tricky to get a bar for, as the intake manifold is very tall.

I should mention that I am also guilty of the same assumptions that you are making. I spent $200 on my racing dynamics front strut brace. Then I learned about this, and it started to make far more sense why I could BARELY notice the difference from it.

[moroza]

I'd add to the note about the importance of brands to make sure they're EU-made as well. I've seen enough quality control issues with Chinese-made Lemförder parts to lump them in with any other no-name junk. German Lemförder is correct.

Regarding the front...

Once that bar has any bend in it, it will simply deform more in the direction of the bend rather than bearing the load. Don't get me wrong, it will still transfer some load across, but with all the different bars being between 100-300 USD, Im going to pick one that is actually structurally sound. Reducing the angle of the bends will lead to it feeling stiffer, but is never as good as a straight bar.

No, but it can be Good Enough. I noticed a meaningful difference between no bar and the Mason Engineering one. Check out the J-arm on the steering setup of my 4x4 Toyota (or my 2-ton Ford van) for examples of highly bent steel that effectively and reliably transfers tension and compression loads.

FWIW, an M60 without its acoustic cover and with a vertically relocated PS tank (trivial, at least with a single-circuit reservoir) could clear a straight-across bar.

Your writeup does not apply to the 525iX. That said, anyone in North America with an iX probably isn't going to be confused by your spreadsheet anyway.

Regaring the polemic about control arm bushings - do you refer specifically to the lower control arms?

Lemförder is the spelling.

Thrust arm bushings varied with model; they did not all use 605 ones.

For consistency, list the PNs of the thrust arms too.

IMO, going cheap on tierods and swaybar links is ok.

Have you ever seen a steering giubo in need of replacement? I honestly have not.

A note about pitman arm pinch bolts: these are class 12.9 M10x1.5 fasteners, and the application seems to require every available bit of strength. Pitman arm height must be adjusted any time the pitman arm or idler arm are loosened. Furthermore, a common source of slop, especially after everything else has been replaced and the hair-tearing-out phase has begun, is that bolt having worked loose. My practice has been to get new hardware, torque to yield, and use red threadlocker. Furthermore, in one case I plastically deformed the pitman arm in a press by 0.5mm, making more of the bolt's clamp load go towards holding the splines tight and less towards deforming the arm elastically.

IMO, if you're mentioning bumpsteer plates, you should mention camber plates as well.

No word on strut mounts or spring pads?

~~~~~~~~~~~~~~

Regarding the rear...

I don't think there are any SLS-specific brackets on the subframe, only on the body for the accumulators. Every E34 subframe I've seen has mounts for the regulator valve.

E32 740 also used the slide bearings. E32 735 used the lower-spec bushings.

E32 trailing arms are identical to the bigger E34 arms. The difference in offset is only in the outer hub.

I've seen enough worn-out slide bearings to consider "immortal" an exaggeration. They do seem to stay tight longer than the bushings.

The center subframe mount is about the best contender for "immortal" that's still a wear item. I've seen them squished, never seen one loose or broken.

IME, dogbones other than genuine or Lemförder are a waste of time.

15 years of cobbling together E34 and driving them to all sorts of places, and I've never bought new halfshaft bolts.

The M40 page

[Singing6]

Your writeup does not apply to the 525iX. That said, anyone in North America with an iX probably isn't going to be confused by your spreadsheet anyway.

The rear suspension actually shares a large portion of the components, but you are correct that the front list is irrelevant.

Regaring the polemic about control arm bushings - do you refer specifically to the lower control arms?

It is actually aimed at the rear trailing arm bushing/bearings, thrust arm bearings, and lower control arm bearings. I desperately hope that people understand that poly is not a good replacement when the loading is that high while also requiring so many degrees of freedom. Add to that the fact that there are MUCH better options available for our chassis and there is no good reason to get the poly control arm bushings.

Lemförder is the spelling.

I will endeavor to go in and fix it. Google sheets does not have a spell checker, I know there are errors all over the place that need to be fixed.

Thrust arm bushings varied with model; they did not all use 605 ones.

Well aware. Nice little thread there btw. I only listed a part number so that, as mentioned in the disclaimer, those who want to minimize NVH can get the stiffest factory bushings. I have updated the part number to 31121136607 as guided by your thread.

For consistency, list the PNs of the thrust arms too.

Done.

IMO, going cheap on tierods and swaybar links is ok.

I normally go with the Rein swaybar endlinks, but when I was putting together the list they were on backorder from FCP Euro. I am debating adding a brand column to the list so I can really get specific. Also because I have gotten many a message from people that apparently dont know how to click on a hyperlink and are asking what brand I am recommending.

Have you ever seen a steering giubo in need of replacement? I honestly have not.

Nor have I. That said, I do have to wonder how many E34/32 owners have gone down into that area to look at stuff. I suspect many will find all of their pedal bushings are GONE. Anyway, it's cheap and feels good to replace.

A note about pitman arm pinch bolts: these are class 12.9 M10x1.5 fasteners, and the application seems to require every available bit of strength. Pitman arm height must be adjusted any time the pitman arm or idler arm are loosened. Furthermore, a common source of slop, especially after everything else has been replaced and the hair-tearing-out phase has begun, is that bolt having worked loose. My practice has been to get new hardware, torque to yield, and use red threadlocker. Furthermore, in one case I plastically deformed the pitman arm in a press by 0.5mm, making more of the bolt's clamp load go towards holding the splines tight and less towards deforming the arm elastically.

Our conversations in THIS THREAD are what led me to add the pitman arm bolts to the list. I will also add your notes on "pre-clamping" the pitman arm to the disclaimer page.

IMO, if you're mentioning bumpsteer plates, you should mention camber plates as well.


No word on strut mounts or spring pads?

I'm trying to keep this document "factual" in terms of how stuff should be set up. Springs, dampers, STM's all MASSIVELY effect how the car rides. I'm trying to avoid going down that rabbit hole, as I believe that the only way for people to truly figure out what is best for them is to drive all the options. Also, I actually have very little experience with aftermarket adjustable STM's and the like. Other than to HIGHLY recommend the Moosehead rear STM's for any lowered e34's that are not on coilovers. OK, fine. Maybe I will add some of that stuff to the list. Anyway, the stuff that is currently on the lists is what EVERY e34 should have.

The bumpsteer plates kinda sneaked in there to make sure the control arm angles are still good. Interestingly, I have not found E34's to exhibit "BUMP--->STEER" characteristics. Even when slammed with the LCA's pointing at the nearest geostationary satellite, the car will not dive off in random directions. It will just have an overly harsh ride. When I have installed the bump steer plates, it has always ended up feeling like the effective spring and damping rate was lowered, that is, the car rides much smoother after install. It was a pleasant surprise.

I don't think there are any SLS-specific brackets on the subframe, only on the body for the accumulators. Every E34 subframe I've seen has mounts for the regulator valve.

There are two SLS specific things that I have seen, the mount on the left side of the diff and one in between the two RTABS on the right side. Every subframe I have seen has the mount next to the diff. The one on the right seems to be on some and not others. I have not really looked hard at a touring subframe with SLS though, so if you have better info (pics) please share. Oddly enough, the only car I have seen the bracket on the right on, is my original 11/95 525i sedan subframe, but then, my car is all kinds of odd being soooo late production.

E32 740 also used the slide bearings. E32 735 used the lower-spec bushings.


E32 trailing arms are identical to the bigger E34 arms. The difference in offset is only in the outer hub.

Updated the text to reflect this.

I've seen enough worn-out slide bearings to consider "immortal" an exaggeration. They do seem to stay tight longer than the bushings.

Changed the wording to reflect this. Either way, If you are pulling out the trailing arm, I consider it a waste of money to put the stock rubber bushings in rather than these slide bearings.

15 years of cobbling together E34 and driving them to all sorts of places, and I've never bought new halfshaft bolts.

In the 5-ish years that I have been playing with them, I have found the occasional stripped head. Often times though it is because the dirt was not cleaned out of the head and so the bit did not get full engagement. Either way, it is a part I want people to have a few spares lying around for, just in case.

The M40 page

Hopefully you also saw the note when you mouse over it!

Check out the J-arm on the steering setup of my 4x4 Toyota (or my 2-ton Ford van) for examples of highly bent steel that effectively and reliably transfers tension and compression loads.

Would love to see pics. Either way, I stand by my statements regarding strut braces. They all seem to run the 100-300 USD price range and I am trying to get people to recognize what will give them the best bang for the buck. Also looks like I was getting the miller performance and mason engineering bars mixed up. the Miller performance bar is 100% eye candy. Have worked with it personally. all it does is flex. The mason engineering one looks OK, but still not as good as it could be. Will update the list to reflect this.

I'd add to the note about the importance of brands to make sure they're EU-made as well. I've seen enough quality control issues with Chinese-made Lemförder parts to lump them in with any other no-name junk. German Lemförder is correct.

Lets work out the other kinks first. Either way, I have removed the Lemförder parts that are problematic. Have had good luck so far with the ones that remain. I know all of the Lemförder slide bearings ordered these days are china production, I got mine when they were still german production. But the bearings from china seem to do well. It is the bushings that you have to be careful with, particularly fluid filled ones.

-------------------

Phew, that was a big one to go through. Looks like I still did pretty good though!

[W124]

I've got a straight strut bar in my 530iT...

20190621_132627.jpg

It may look crude, but the difference was huge when I had my unknown brand (maybe H&R) lowering springs installed. I'm now riding on Vogs and they are soft enough to where I don't think the bar is as critical, however I haven't had the bar off since. I was able to clear the power steering reservoir, as you can see it's the metal canister. Strut bar is worth it if only as a place to lean on while working under the hood lol.

The Moosehead spherical bushings are linked in the spreadsheet but they are out of stock. There are other options out there such as these:

https://www.akgmotorsport.com/produc...minum-e32-e34/

Any thoughts? $150 seems reasonable.

Also, $280 from turner: https://www.turnermotorsport.com/p-3...-arm-bearings/

[Singing6]

I've got a straight strut bar in my 530iT...

20190621_132627.jpg

It may look crude, but the difference was huge when I had my unknown brand (maybe H&R) lowering springs installed. I'm now riding on Vogs and they are soft enough to where I don't think the bar is as critical, however I haven't had the bar off since. I was able to clear the power steering reservoir, as you can see it's the metal canister. Strut bar is worth it if only as a place to lean on while working under the hood lol.

The Moosehead spherical bushings are linked in the spreadsheet but they are out of stock. There are other options out there such as these:

https://www.akgmotorsport.com/produc...minum-e32-e34/

Any thoughts? $150 seems reasonable.

Also, $280 from turner: https://www.turnermotorsport.com/p-3...-arm-bearings/

I commented on the other options in the “Readme”. Check Angry Ass to see if they have stock. It is linked on the sheet. Or just wait for them to come back in stock.

A more detailed word on the alternatives is as follows:

The Mooseheads actually have a moderate NVH increase, the other options for spherical bearings have a LARGE increase in NVH. This is because both the inner and outer races are metal, as oppose to the Mooseheads with a metal inner race and "Nylatron" outer race that allows some give.

The turner monoballs are one-time press to some extent thanks to the knurling. Im sure they can be pressed in a second time, but each time you do it, they will get looser in that seat.


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[moroza]

The rear suspension actually shares a large portion of the components, but you are correct that the front list is irrelevant.

Yes, I was referring to the front, as that's where I saw the note that the info applies to "all" E34. Tangentially, the iX had a locking rear diff that I'm passingly interested in retrofitting to my car.

It is actually aimed at the rear trailing arm bushing/bearings, thrust arm bearings, and lower control arm bearings. I desperately hope that people understand that poly is not a good replacement when the loading is that high while also requiring so many degrees of freedom. Add to that the fact that there are MUCH better options available for our chassis and there is no good reason to get the poly control arm bushings.

No argument from me. The people who designed the E34 and sweated over minutae of bushing design knew WTF they were doing more than 99% of those owners who throw in every "upgrade" they can think of just because it's "high performance" or for racecars. "Racing" is to car parts what "tactical" is to camping equipment.

Well aware. Nice little thread there btw. I only listed a part number so that, as mentioned in the disclaimer, those who want to minimize NVH can get the stiffest factory bushings. I have updated the part number to 31121136607 as guided by your thread.

Er... if you want to minimize NVH, don't go for the stiffest bushings. Unless you know what you're doing, go for the *correct* bushings, which vary by model and are not one-size-fits-all. 607 isn't meant for any E34, and IME it's unnecessarily firmer than 605 or 606.

I'm trying to keep this document "factual" in terms of how stuff should be set up. Springs, dampers, STM's all MASSIVELY effect how the car rides.

So do spherical bearings. I see why you want to avoid the can of worms of springs and shocks, but strut mounts and spring pads deserve entries, IMO.

The bumpsteer plates kinda sneaked in there to make sure the control arm angles are still good. Interestingly, I have not found E34's to exhibit "BUMP--->STEER" characteristics. Even when slammed with the LCA's pointing at the nearest geostationary satellite, the car will not dive off in random directions. It will just have an overly harsh ride. When I have installed the bump steer plates, it has always ended up feeling like the effective spring and damping rate was lowered, that is, the car rides much smoother after install. It was a pleasant surprise.

Not everyone lowers their car (at all, or to the point that balljoint spacers are necessary). I'm intrigued by the note about a smoother ride. All I'd expect from balljoint spacers is better cornering grip from decreased camber when the outside suspension is compressed in a turn.

There are two SLS specific things that I have seen, the mount on the left side of the diff and one in between the two RTABS on the right side. Every subframe I have seen has the mount next to the diff. The one on the right seems to be on some and not others. I have not really looked hard at a touring subframe with SLS though, so if you have better info (pics) please share. Oddly enough, the only car I have seen the bracket on the right on, is my original 11/95 525i sedan subframe, but then, my car is all kinds of odd being soooo late production.

The right bracket is for the warning switch, unnecessary IMO.

Changed the wording to reflect this. Either way, If you are pulling out the trailing arm, I consider it a waste of money to put the stock rubber bushings in rather than these slide bearings.

I disagree. I've not tried brand new bearings, but I did have used bearings in my 544iT, and brand new genuine bushings in the 525iT. My impression is that the bushings ride a bit softer.

In the 5-ish years that I have been playing with them, I have found the occasional stripped head. Often times though it is because the dirt was not cleaned out of the head and so the bit did not get full engagement. Either way, it is a part I want people to have a few spares lying around for, just in case.

If stripped, sure. If not damaged, there's no need to replace them IMO; they aren't TTY. One could argue that the serrations under the head need to be fresh, I suppose.

Hopefully you also saw the note when you mouse over it!

I don't like L4 engines, but the M4x isn't bad for what it is. Some circumstances might favor a 518 over a "greater" model. Light weight in the front is just one of the perks.

Would love to see pics. Either way, I stand by my statements regarding strut braces. They all seem to run the 100-300 USD price range and I am trying to get people to recognize what will give them the best bang for the buck. Also looks like I was getting the miller performance and mason engineering bars mixed up. the Miller performance bar is 100% eye candy. Have worked with it personally. all it does is flex. The mason engineering one looks OK, but still not as good as it could be. Will update the list to reflect this.

Or for an example closer to home:

[Singing6]

Er... if you want to minimize NVH, don't go for the stiffest bushings. Unless you know what you're doing, go for the *correct* bushings, which vary by model and are not one-size-fits-all. 607 isn't meant for any E34, and IME it's unnecessarily firmer than 605 or 606.

Well, I did drive my 525i with the 607 for a while before upgrading to the Mooseheads. I personally believe that everyone should run the Mooseheads, but some owners really put OEM ride over added feedback and control (which is perfectly fine for them to do). I will add a note in the readme.

So do spherical bearings. I see why you want to avoid the can of worms of springs and shocks, but strut mounts and spring pads deserve entries, IMO.

You have convinced me. Now I will have to write up on the front STM versions (will just link the thread on that) and maybe split them up into tabs. I will split the struts between the front and rear lists. I am likely going to stick to factory STM's up front (rather than adjustable ones) until I have more experience with the aftermarket options. So far I have only ever used the BC Racing ones included with the coilover kit. Information welcomed on this topic. Also, the largest NVH increase from a suspension component I have had so far is the adjustable STM's up front from BC racing. Maybe that is because they were the last rubber suspension part to go, or just because they play that big of a role, but you hear the road and brakes a lot more with them.

Not everyone lowers their car (at all, or to the point that balljoint spacers are necessary). I'm intrigued by the note about a smoother ride. All I'd expect from balljoint spacers is better cornering grip from decreased camber when the outside suspension is compressed in a turn.

I'm going to state here and now that I think the stock ride height of e34's is a war crime. The effort you yourself went through to lower the car while preserving the stock ride quality says a LOT. But I also respect those who want to preserve the car in the form it came from the factory. I put in the bump steer plates because I feel that most of the people that are going to be using this list are going to be on aftermarket springs and dampers. I should also mention that I installed the 1" bump steer plates while still on the H&R springs, not on my current coilovers. So all the differences I noted are back when I was at a "normal" ride height. You don't need to be super low to benefit from it. I am working on my own bump steer plates that fit better and are offered in taller sizes for those like me that are really low. (My LCA sit about level at my current ride height, even with the 1" roll center spacers. I would like a 1.5" set, and I know people that need 2")

And don't get me wrong, going between a lowered car with the roll center correction plates, and one without, there is a noticeable increase in cornering stability. But that is not the first thing that you will notice after installing them. It is the improved ride.

The right bracket is for the warning switch, unnecessary IMO.

Noted. Is it odd to have had that on my 95 525 sedan? I have yet to see it on any other sedan 525i's spanning 93-95.

I disagree. I've not tried brand new bearings, but I did have used bearings in my 544iT, and brand new genuine bushings in the 525iT. My impression is that the bushings ride a bit softer.

Yep, there is no denying that there will be a difference, but I think it is so minor that it is worth all the benefits of improved control of the trailing arm movement. I am also obviously a biased source. It is up to the owner to decide, and I have said as much in the readme tab.

If stripped, sure. If not damaged, there's no need to replace them IMO; they aren't TTY. One could argue that the serrations under the head need to be fresh, I suppose.

I'm not asking them to change all of them, only to have spares on hand. I changed the part from "need" to "should" to reflect this.

Or for an example closer to home:

Cant speak for the Toyota parts, but I can speak for the BMW ones. Pretty darn sure the uppers are forged, but also note how the cross-section of the upper changes dramatically when it has the bend out of line with the end points. It gets almost twice as thick to counteract this buckling force. I have yet to see a strut brace do that, all the ones I have seen in person maintain a constant cross section. Either way, the parts you show there are a demonstration of how having a bend in the part dramatically affects how it transfers load.



------------

You are bringing up great points and I am very happy to be able to improve the lists based on this kind of input!

[moroza]

Can you explain how the spacers could improve the ride?

I agree with you regarding the OEM ride height. It's unconscionable, and only an "OE for the sake of OE", a rally car, or an eastern European car should be that high.

Given the multitude of options and people's preferences, I can see avoiding specifics about springs and shocks. Mounts, however, are much more limited: it's basically V1 (why would you), V2 (why would you), V3, or aftermarket racing.

Note that E32 front springs and pads, the upper of which is thicker than E34 and castellated for further NVH reduction, fit E34 front hardware. So do E30 and E28 springs and pads. I'm using compressed E34 springs, E32 upper pads, and V3 mounts with an E90 upper spring perch, which lowers ~7mm compared to the stock V3 perch. V1 and V2 cannot do this, are more expensive, and otherwise no better as far as I can tell. V1 is furthermore getting harder to find, as are shocks to fit. I consider my front setup to be nearly perfect for my tastes, which favor the bone-stock ride but not the height.

Agreed that the RTAB difference is quite insignificant.

Yes, I'd say it's weird to have that on a late sedan. On a related note, I've noticed some earlier automatic cars had the clutch over-center bracket, while later automatics didn't.k

[Singing6]

Can you explain how the spacers could improve the ride?

I agree with you regarding the OEM ride height. It's unconscionable, and only an "OE for the sake of OE", a rally car, or an eastern European car should be that high.

Given the multitude of options and people's preferences, I can see avoiding specifics about springs and shocks. Mounts, however, are much more limited: it's basically V1 (why would you), V2 (why would you), V3, or aftermarket racing.

Note that E32 front springs and pads, the upper of which is thicker than E34 and castellated for further NVH reduction, fit E34 front hardware. So do E30 and E28 springs and pads. I'm using compressed E34 springs, E32 upper pads, and V3 mounts with an E90 upper spring perch, which lowers ~7mm compared to the stock V3 perch. V1 and V2 cannot do this, are more expensive, and otherwise no better as far as I can tell. V1 is furthermore getting harder to find, as are shocks to fit. I consider my front setup to be nearly perfect for my tastes, which favor the bone-stock ride but not the height.

Agreed that the RTAB difference is quite insignificant.

Yes, I'd say it's weird to have that on a late sedan. On a related note, I've noticed some earlier automatic cars had the clutch over-center bracket, while later automatics didn't.k

My guess as to why is simply that the control arms are not fighting the motion of the wheel. Maybe because travel is more linear in those control arm angles? Have not gotten far enough in my engineering classes tbh. Interesting note on trying to convert everything to V3 mounts. It would sure simplify my lists. Be warned that I'm going to always spec out the factory components that give the most low. The E90 drop hats (if your springs are tall enough to prevent the spring from unseating at full droop) and 3mm spring pads.

[moroza]

The most low would be no spring pads at all. Stock setup on V1 and V2 is 3mm lower, 9mm upper. On V3, 3mm lower and 3mm upper. E32 uppers 31331135589 are 10mm and fancier. All lower pads are 31331124322.

[Singing6]

The most low would be no spring pads at all. Stock setup on V1 and V2 is 3mm lower, 9mm upper. On V3, 3mm lower and 3mm upper. E32 uppers 31331135589 are 10mm and fancier. All lower pads are 31331124322.

No spring pads sounds like a bad idea, which is why i never did it. 3mm spring pads all the way around is what i recommend.


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[sbeckman7]

Another undercarriage brace you may not have come across: https://www.schmiedmann.com/displayp...&produkt=uks34
image_119335_big.jpg

[Singing6]

Another undercarriage brace you may not have come across: https://www.schmiedmann.com/displayp...&produkt=uks34
image_119335_big.jpg

I do recall seeing this at some point, but thanks for finding it again. I suspect that the e31 brace is carrying most of the loading that this does. Anyone actually tried this?


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[fo3]

trailing arm rear suspension like BMW did make me sad. What's the perfect solution and how can I get it ? (besides buying a M5 and or E39 :-) )
No one likes changing the stock rubber RTABs, and I agree poly doesn't work with the badly designed and thought out compromise of the dogbones (I don't agree that BMW knew what they were doing with that whole compromise and that it can't be improved. There's got to be some bolt on replacement that works better and is more serviceable)

[Singing6]

trailing arm rear suspension like BMW did make me sad. What's the perfect solution and how can I get it ? (besides buying a M5 and or E39 :-) )
No one likes changing the stock rubber RTABs, and I agree poly doesn't work with the badly designed and thought out compromise of the dogbones (I don't agree that BMW knew what they were doing with that whole compromise and that it can't be improved. There's got to be some bolt on replacement that works better and is more serviceable)

OK, to start, I disagree with your opinion of the rear suspension on the E34. It is VERY predictable and well behaved. The M5 slide bearings perfect it. If you read through the lists, you will see the parts required. Also, E39's have much less feedback to the driver and IMO, are much worse off for it. You don't need to buy an M5 to get these parts. The trailing arms can be stolen from a 740 or 750 if you are dead against getting new parts (but who hates new parts, besides the wallet?).

Also remember that BMW designed this suspension in the mid 80's. Of course it will look archaic by today's standards. But if you set it up like mine, it sure wont DRIVE like it is a 40 year old design.

This list IS the perfect solution. If you don't believe me, I invite you to come drive my car and see how you are wrong.

[moroza]

I agree the E34 rear suspension is a bit primitive by modern IRS standards, and with relatively high unsprung weight.

[fo3]

I just checked with my 1990 eu/au 525i and yeah, same as you say, smaller hubs and bearings. I'm never going to find a 7 series or e34 touring here, so best chance is just bolting up a 535i set up.
Everything suspension and brake wise in my 525i is new, I'm just not happy with the poly kmac rtabs

So the way forward you suggest is getting a complete 535i rear assembly, refreshing what is tired, welding on IE camber and g-istic toe etc, then m5 bearings for the trailing arms.

I'll further check part numbers of anything I can reuse because it's all new, otherwise I know what part numbers I need for all the bits and pieces thanks to your list

After that changing diff and bolting it up right? (does the 525i diff fit on the 535 axles, bushes you list and the carrier?)

[Singing6]

I just checked with my 1990 eu/au 525i and yeah, same as you say, smaller hubs and bearings. I'm never going to find a 7 series or e34 touring here, so best chance is just bolting up a 535i set up.
Everything suspension and brake wise in my 525i is new, I'm just not happy with the poly kmac rtabs

So the way forward you suggest is getting a complete 535i rear assembly, refreshing what is tired, welding on IE camber and g-istic toe etc, then m5 bearings for the trailing arms.

I'll further check part numbers of anything I can reuse because it's all new, otherwise I know what part numbers I need for all the bits and pieces thanks to your list

After that changing diff and bolting it up right? (does the 525i diff fit on the 535 axles, bushes you list and the carrier?)

Pay attention to the trailing arms section for the 525i list. I put in a part to convert the inner hub flanges to 525it ones so you can bolt up 525i axles. If you do a full 535i rear assembly pull, then just pop the output flanges out of the diff and slap them on your 525i diff. If you use the 535i hub flanges and axles, it will all bolt up. I have actually done both. I started with the 525it hub flanges and ran my 525i axles but then swapped over to the 535i parts (and changed the cv joint boots, which is a must).

And no wonder you hate it! You have poly in the RTAB’s!


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[moroza]

USDM E34 535i got 188 diffs, but at least some GDM had 210. If Aussie 535i also got 210, you'll need to use the bigger axles as well.

[Singing6]

USDM E34 535i got 188 diffs, but at least some GDM had 210. If Aussie 535i also got 210, you'll need to use the bigger axles as well.

Do we know how it was decided what M330b35's got the 210mm? Was it part of some sports package? I think I need to add this as a note to the README, so looking for more info.

[danespann]

Do we know how it was decided what M330b35's got the 210mm? Was it part of some sports package? I think I need to add this as a note to the README, so looking for more info.

I was under the impression that all non-USDM 535i's had the 210mm. Kent (ibob4tacoz) has a slicktop car here in Phoenix that was imported from Spain and has a 210mm large case 3.45 open diff.

[sugaki]

Although people have differing opinions on suspension setups, I think there probably are general truths about certain setups (Bavauto being undersprung, Bilsteins being too crashy with their high-speed valving, etc) worth mentioning.

[Singing6]

Although people have differing opinions on suspension setups, I think there probably are general truths about certain setups (Bavauto being undersprung, Bilsteins being too crashy with their high-speed valving, etc) worth mentioning.

You are correct to a point. I think there is value in laying that out, but should be in a different thread.


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