Err no, unless you think your springs interfere with the dampers, as the torsion can be seen as an increase in spring rate, polybush drops under it's own weight if you have the whole arm hanging off it, but so does rubber with that weight, disconnect your lower arm for instance and see how freely it moves, my experience with poly is unless you take the time to set them up correctly or you have a good fit out of the box they stick.GuidoK said:So if it acts like a spring it still interferes with the dampening of your car. Affecting the spring characteristic of the main spring.
the polybushed suspension drops under its own weight, so if there is any resistance, its negleable. Less of an effect to the main spring and shock.
Thus better
RTAB replacement...
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And that's fair enough.
Artful-Bodger said:
Amen. Was just considering unsubscribing to my own thread!
Mike
GuidoK said:
Yes, but usually pertaining to the thread
Mike
I dont think it was off topic?
Your question was about either oem bushings or go poly?
Everything written here was in light of that I think? Having both supporters and opposers of poly bushings cq. rubber bushings giving their own arguments.
I can think of countless threads here on this forum that went way more off topic than this thread.
Your question was about either oem bushings or go poly?
Everything written here was in light of that I think? Having both supporters and opposers of poly bushings cq. rubber bushings giving their own arguments.
I can think of countless threads here on this forum that went way more off topic than this thread.
As I said previously, oem with limiters is probably the best solution. My experience with poly has not been any noticeable increase in nvh or squeaking. Massively better than the tired original bushings, the improvement was immediately apparent and at least I'll never have to touch them again.
Ewazix said:
Agreed. I kinda love these kind of threads
I've gone powerflex purely from a fit and forget perspective. Too many other things to maintain to want to do them again.
I can't help but cringe though whenever anyone argues that it should be OEM because the manufacturer knows best and did it for a reason. I always think it's worth bearing in mind the ONLY reason they make cars is for profit. Be it in the original sales price or the lifetime servicing.....
Darkangelv2 said:
one only has to take a glance at my car to know what I think of OEM (or step on the pedal to get a better impression :lol: )
Look at OEM this way: if you take away the body and interior, the z4 is basically your run of the mill 3 series. Not very sportscar now is it? :roll: :lol:
your mis reading what's written, the issue is BMW use rubber in the RTAB bush because it's the best material to handle the multi axis movements in that application, not BMW is always right, Lotus use a similar arrangement in the Esprit and Excel, they handle just fine!
I've had a similar (albeit less informed from my side) 'discussion' with Guido about the merits or otherwise of polybushing this particular application. There's obviously differing opinions out there.
What I base my opinions of having run both poly and new oem + limiter back to back, is that I found I had more confidence in the rear end with the oem rubber bush. The poly didn't make any noise it must be said and was installed by a reputable shop. The shop i now use who have raced e46 m3s since early 2000s do not use poly for the rtabs, everywhere else they do.
Guido, just for fun one day try the oem + limiter and tell us again we're all wrong! Seriously though I appreciate your argument for poly, but in this specific application I'm definitely not convinced it's the right material.
What I base my opinions of having run both poly and new oem + limiter back to back, is that I found I had more confidence in the rear end with the oem rubber bush. The poly didn't make any noise it must be said and was installed by a reputable shop. The shop i now use who have raced e46 m3s since early 2000s do not use poly for the rtabs, everywhere else they do.
Guido, just for fun one day try the oem + limiter and tell us again we're all wrong! Seriously though I appreciate your argument for poly, but in this specific application I'm definitely not convinced it's the right material.
TomK said:
I'm not so much interested in opinions, but more in facts and I've disproven a few misguided facts here.
Like the poly bushings binding and thus interfering with the spring tension (which was originally your point). Myth busted! the suspension moves freely under its own weight within the travel of the shock.
Or that the z4m was using 'different rtab's' than the normal Z4: Myth busted! Every amateur could have compared partnumbers and seen that they are the same. The ETK isnt wrong... (on the e46 it is a different part though and thats probably the reason this myth also goes round in the z4 community)
So whatever reason someone chooses for either poly or normal rubber I dont care. But I do care about the misinformation presented as facts.
I wrote that the binding issue was originally your point.
from this topic:
http://www.z4-forum.com/forum/viewtopic.php?f=9&t=62834
The next thing about being confused on z4m bushting difference was never your point and I didnt write that, or at least not specifically. The 'or' is in general. I wouldnt know how else to phrase it. Maybe one can read it 2 ways.
from this topic:
http://www.z4-forum.com/forum/viewtopic.php?f=9&t=62834
TomK said:
TomK said:
The next thing about being confused on z4m bushting difference was never your point and I didnt write that, or at least not specifically. The 'or' is in general. I wouldnt know how else to phrase it. Maybe one can read it 2 ways.
Anyway, a quick bit of reading suggests the upper outer balljoint can also be used on the lower arm allegedly as per M3, so I have two of these on order and will do a trial fit to confirm this, if it's correct that eliminates the need for any flexible bush in the upright and gives a far better control of the movement!
There are group N bushes available for the inner arm joints but these are expensive, seeing as the subframe is carried on isolating bushes it may be possible to use balljoints on the inner points without too much penalty in NVH on the road, that's something I will try back to back once I either find a suitable joint in the parts catalogue or make up a set with spherical bearings.
The RTAB bolts direct into the chassis so fitting a balljoint here would be a big no no on the road, I can't yet find any info on an unprated group N spec RTAB, the Si/M spec bush is different to the earlier bush I have here so it might be the later bush with limiters would be the way to go, although I am looking at the Meyle bush to see if that is a harder bush than standard or installs under more compression, however short of buying one and testing it with a durometer I don't see a way of comparing them, so I will probably have to just spend the cash buy one of each and test them to find out!
On the subject of limiters these are quite popular among the track drivers but before I try fitting anything like this I want to measure the deflection in the housing in movement from full bump to full droop, they may be fine on a race car with the limited suspension movement but could possibly bind and impart twisting loads into the arm/chassis on the lousy public roads .
So that's the winter spare time sorted, when I get definite info I will post it and make a list of possible combinations!
There are group N bushes available for the inner arm joints but these are expensive, seeing as the subframe is carried on isolating bushes it may be possible to use balljoints on the inner points without too much penalty in NVH on the road, that's something I will try back to back once I either find a suitable joint in the parts catalogue or make up a set with spherical bearings.
The RTAB bolts direct into the chassis so fitting a balljoint here would be a big no no on the road, I can't yet find any info on an unprated group N spec RTAB, the Si/M spec bush is different to the earlier bush I have here so it might be the later bush with limiters would be the way to go, although I am looking at the Meyle bush to see if that is a harder bush than standard or installs under more compression, however short of buying one and testing it with a durometer I don't see a way of comparing them, so I will probably have to just spend the cash buy one of each and test them to find out!
On the subject of limiters these are quite popular among the track drivers but before I try fitting anything like this I want to measure the deflection in the housing in movement from full bump to full droop, they may be fine on a race car with the limited suspension movement but could possibly bind and impart twisting loads into the arm/chassis on the lousy public roads .
So that's the winter spare time sorted, when I get definite info I will post it and make a list of possible combinations!
you just want the rear trailing arm bushings?
Go for powerflex PFR5-3608
http://www.ebay.co.uk/itm/POWERFLEX-BMW-REAR-TRAILING-ARM-BUSHES-Z4-ALL-MODELS-E85-E86-/231143068863
You need some sort of tool to press the original bushing out. You can get either a specifice tool for that bushing or a generic bush pressing kit (with which you can press all kinds of bushings).
That is to just get the original bushing out. Maybe you can even do that with hammer&chisel although I wouldnt advice that.
To get the poly ones in you dont need any tools, they just hand fit in.
Go for powerflex PFR5-3608
http://www.ebay.co.uk/itm/POWERFLEX-BMW-REAR-TRAILING-ARM-BUSHES-Z4-ALL-MODELS-E85-E86-/231143068863
You need some sort of tool to press the original bushing out. You can get either a specifice tool for that bushing or a generic bush pressing kit (with which you can press all kinds of bushings).
That is to just get the original bushing out. Maybe you can even do that with hammer&chisel although I wouldnt advice that.
To get the poly ones in you dont need any tools, they just hand fit in.
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