Polyurethane and eurethane - are they the same

[BigKriss]

From the UCC mailing list;

> Here's one for all you armchair racers who think that Eurethane is
> something that should be installed on a vehicle.
>
> An example of E34 Eurethane thrust rod bushings after only a few
> thousand miles. http://www.koalamotorsport.com/thrustrod.avi
>
> The single biggest thing you can do to downgrade your stock BMW
> suspension is use Eurethane bushings. I've said it for years, but now
> I have video proof, bad as the video is.
>
> Brett Anderson
> KMS

Found this link today from Brett Anderson (Koalamotorsport). Shows a thust arm which is in bad shape. I'm thinking of putting on polyurethane bushings (both lower and upper arms). Any thoughts guys? (http://www.koalamotorsport.com/thrustrod.avi)

[epj3]

I think they ment urethane... I've never heard of "eurethane"... but urethane (aka polyurethane) is tougher than the rubber or grease filled rubber bushings bmw makes OEM for our cars... not sure what they are trying to say.

Plus, urethane bushings don't have to be preloaded like the oem bushings do. Personally I'm going with the gruntsbushings.com urethane control arm bushings.

[Jon K]

I think they ment urethane... I've never heard of "eurethane"... but urethane (aka polyurethane) is tougher than the rubber or grease filled rubber bushings bmw makes OEM for our cars... not sure what they are trying to say.

Plus, urethane bushings don't have to be preloaded like the oem bushings do. Personally I'm going with the gruntsbushings.com urethane control arm bushings.


The point is that the OE bushings do have some play in them being rubber, the urethane do not and they seperate from the control arm... easy to follow.

[epj3]

The point is that the OE bushings do have some play in them being rubber, the urethane do not and they seperate from the control arm... easy to follow.
Oooh I see what they are saying now. So, really, should I go with M5 bushings over urethane?

[Rory535i]

they seperate from the metal because they don't have the same bonding properties as rubber...

[Mobius]

Plus, urethane bushings don't have to be preloaded like the oem bushings do. Personally I'm going with the gruntsbushings.com urethane control arm bushings.ANY thrust arm bushing needs to be tightened at ride height. This isn't preload; you're preloading the bushings if you're tightening them with the wheels hanging down.

They need to be tightened at ride height in part because the inner metal sleeve of the bushing can not rotate in its mount - and if it could, you'd eat up the thrust arm mount in no time.

That said; I believe polyurethane bushings, especially in the thurst arm, belong only on strictly track cars (and not for you "oh lol my car is a track car FOR THE STREET" people, either). The TA bushing needs a certain amount of flex to protect other suspension components from damage. If you use a hard bushing here, you're only shortening the life of most other components of the front axle. If you look at the stock bushing, there's a LOT of design in it - there's none in a poly bushing.

Not to mention the fact that I wouldn't be surprised in the least if most of the people who peddle poly bushings online are anything more than people with some pipe and a can of liquid polyurethane in their garage. The bushing in the video certainly seems to have been made in this fashion.

If you can find quality, properly built poly bushings, then they can be beneficial in certain applications. However, even a quality poly bushing does not belong in the thrust arm - in my opinion. Shitty, 'home made' poly bushings (like those in the video) belong nowhere.

[niall]

(and not for you "oh lol my car is a track car FOR THE STREET" people, either).

thats very opinionated. and not true in all cases,
lots of people prefer stiff suspension and poly bushes area great way
to go, what other suspention components do you think you are shortening the life of? i totally dissagree, i think poly bushes do a better job than factory stuff . as for the design side, id say very little goes into the design of a rubber bush. there is no science here guys.

[Mobius]

thats very opinionated. and not true in all cases,
lots of people prefer stiff suspension and poly bushes area great way
to go, what other suspention components do you think you are shortening the life of? i totally dissagree, i think poly bushes do a better job than factory stuff . as for the design side, id say very little goes into the design of a rubber bush. there is no science here guys.********. There's a TON of 'science' and design in the TA bushing; have you looked at one? There's a reason BMW makes so many different versions of the same bushing.

Through the movement of the front suspension, the TA bushing is forced (and designed) to flex. If you disallow this flex, you move undue stress to the TA ball joint, and by association, the lower arm ball joint and bushing. Also, though I haven't heard of it happening on an E34 - I've seen a couple instances where replacing bushings that are intended to flex with hard poly bushings causes metal fatigue and the eventual destruction of the bushing mount. See here (http://www.twinturbo.net/net/viewmsg.aspx?forum=general&msg_id=1399367).

Anyhow, we've had this discussion before: http://www.bimmer.info/forum/showthread.php?t=7542&page=2&pp=10

I'm not saying polyurethane bushings are ALWAYS bad (in fact, they're probably fine for most every other bushing in an E34's suspension); but they're a poor choice for the thrust arm - in my opinion.

[niall]

well my bro is getting them in his e34 so i gues time will tell, and ill know first hand then if that is the case :)

[Anthony (M5 in Calgary)]

Oooh I see what they are saying now. So, really, should I go with M5 bushings over urethane?

Stiffer than the 750 bushing but still compliant enough for the street. Not hydraulic either.

Anthony

[epj3]

Stiffer than the 750 bushing but still compliant enough for the street. Not hydraulic either.

Anthony
Yea I don't see how the 740 bushing is an upgrade anyways - isn't it an oil filled bushing? It lasts longer but I don't care about life - I want it to be stiffer.

[Rory535i]

Yea I don't see how the 740 bushing is an upgrade anyways - isn't it an oil filled bushing? It lasts longer but I don't care about life - I want it to be stiffer.

if you want stiff, go for polyurethane. simple.

[ichbin]

A polyurethane is a compound with repeating units of (-NH-CO-O-). Urethane alone would never be used as a coating. It is the polymer that is useful.

[MBXB]

In between the OEM/750/M5 bushings and the solid PE bushings, of course, are Bruno's inserts which sandwich and stiffen the OEM or 750 flexible bushings but keep some flexibility.

Mine seem to be holding up well. I haven't had them on long enough to comment on longevity. How about the rest of the guys who installed them? Any feedback and mileage?

[MBXB]

Inserts installed

[Jose]

Poly bushes should be used for track use or hard street driving.You will be killing your suspension due to the lack of any movement in the bushing. You should also bare in mind that the predictibleness of the limits of your suspension becomes almost non existent, oversteer/understeer are reached almost without warning as a rubber bushing flexes and gives you the feel you´re reaching the limits of adhesion, a poly bushing says nothing. If you realy want to upgrade, than replace all bushings front and back, including the silent blocks. It is of no use changing only the steering bushings is you don´t replace , for example the connecting rod bushing. The brand I have the best experience with is the Uk brand Power Flex. Have been using them for years with good results.

[Kalevera]

Hi Kristian.

Gotta add the rest of what they said after the initial message (which, I think, elucidates more of what Brett was communicating):


>They sure made a difference in the handling over the
>> worn out stock ones.


And therein lies the truth behind the popularity of this garbage.

Hands up all those who have replaced brand new rubber bushings with
eurethane?
Anyone?
Bueller?

Change a worn out rubber bushing with a block of wood and it will make a
noticeable improvement. Doesn't mean it's right, or even good.

Brett Anderson
KMS


================================================== ===================

An issue with "U"rethane bushings that everyone fails to take into account
is the degradation in spring rate.

Replace your control arm bushings with urethane and leave stock springs and
shocks in the car and you've just done the equivalent of putting softer
springs in your car. Yeah, there's an upgrade for ya.

Urethane inserts in a stock bushing are a different thing entirely and
shouldn't be compared with the general inability of urethane to do the job
for which it's sold.

If you have a street car, use rubber. If you have a race car, use metal.

Brett Anderson
KMS



>> -----Original Message-----
>> I do think that there is different manufacturer of urethane
>> bushings for the
>> E34... this one might be just a bad one.
>> I have a set that is working great on a 535i turbo (300+ RWHP)
>> that is going
>> often on the track and they are not behaving in the way shown in
>> the movie.
>>
>> This is just a poor designed set. I personnaly was running 750i bushings
>> with delrin inserts that made them close to imposible to move.
>> So let's not just fire on all urethane products.


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

EDIT: BTW, that video is interesting to me because it's the first time I've ever heard the other wrench at KMS *speak*, and I've been there a handful of times now...hahaha.

Also, bet the person who owns that car had the shimmies like a mofo!


best, whit

[Rory535i]

I dont think all the talking or emails or videos in the world will change someone's mind over something like this. if they wanna put poly bushes in their car, they're going to, regardless of what pros or cons they have. best thing is first hand experience to let people come to their own conclusions. As long as they understand the repercussions of putting in poly bushes then I say go for it! I understand all the points people have made so far about the negative side of poly bushes but i don't care. i'm still going to get them for my car and see how i like them. I want to experience what it's like having them in my car and if it results in the premature death of other components then so be it. people say putting a turbo on an engine will shorten it's lifespan yet it doesn't seem to stop too many of us! each to their own i guess.

[DueyT]

Like MBXB said, anyone with some longer term info on Bruno's Delrin inserts? I have 750iL bushings now and was thinking of popping out the green insert and using Bruno's stuff (all thinking about the rear-sub inserts. I just got a whole bunch of all the other rubber from Patrick at BMA and will be putting it in when the rain stops outside...

Cheers,
Duey

[Mobius]

I dont think all the talking or emails or videos in the world will change someone's mind over something like this.Of course, we're all free to waste our money as we see fit. Do what you want, the point is they aren't a 'magical handling fix' that they are usually made out to be - especially not in this application.

[niall]

some of you guys really suck

[Rory535i]

Of course, we're all free to waste our money as we see fit. Do what you want, the point is they aren't a 'magical handling fix' that they are usually made out to be - especially not in this application.

I'm not making them out to be a magical handling fix, I merely want to experience the difference between them and rubber bushes. Also not everyone considers them a "waste of money". No need to treat people like idiots.

[epj3]

In between the OEM/750/M5 bushings and the solid PE bushings, of course, are Bruno's inserts which sandwich and stiffen the OEM or 750 flexible bushings but keep some flexibility.

Mine seem to be holding up well. I haven't had them on long enough to comment on longevity. How about the rest of the guys who installed them? Any feedback and mileage?
I want some but he's been out of stock forever, so that's not an option.

[Robin-535im]

some of you guys really suck

Bwaa ha ha ha!

:)

Lighten up man! Just a bunch of guys talking about cars. No one has any rude intentions here, just that sometimes communications in text can come across wrong. I'll even put in some smiley faces to lighten the mood.

:)

- Robin

[niall]

ok ok
:):):)