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  #51  
Old 29-04-2011, 03:56 PM
UJM3 UJM3 is offline
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I have some Ireland Engineering subframe bushes myself to go in next week hopefully, they have been sitting inmy garage for a couple of weeks now!

I'm prepared for a bit of noise just doing it really to help preserve the subframe as I am of the same opion of some of those mentioned in this thread. Randy Forbes afaik fits this as well as part of his subframe repairs.

Will report back once I have them fitted..
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  #52  
Old 29-04-2011, 04:14 PM
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exdos exdos is offline
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Originally Posted by RST Driver View Post
Ouch, I didn't want to hear that.
I'd read about the squeaking before I decided to fit the Polyurethane bushes, and I decided to ignore the warning


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Originally Posted by RST Driver View Post
What exactly causes the noise exdos? The inner metal part or the urethane surface which is in contact with the subframe?

Best regards,
Phil
The TA bush has a metal tube insert which is clamped tight between the sides of the trailing arm brackets on the rear subframe and the poly bush fits then fits between the metal tube insert and inside the metal sleeve of trailing arm bush holder. In the case of the OEM rubber TA bush, the TA can rotate by stretching and compression of the rubber bush, but in the case of a polyurethane bush, for the TA to rotate, the metal sleeve of the TA bush holder must move over the face of the polyurethane TA bush, and/or the the bush must move around the metal sleeve insert and this creates friction. The bushes come with some silicone lubricant, but the fit of the polybushes is so tight, that there's nowhere for the lubricant to remain. Obviously, heat is generated by the frictional movement of the TA, so what little of the lubricant remains in place after fitting, soon burns away and then you get the sound of polyurethane sliding across metal creating the squeaking noise.

I tried using different lubricants and also making little reservoirs on the fitting surfaces of the polyurethane bushes, to help lubrication to remain in place, but nothing worked for long. It's such a hassle messing around with the trailing arms, that I decided to revert to OEM TA bushes and be finished with the problem once and for all. It was the only mod that I regretted doing.

You've been warned!

OTOH, fitting polyurethane subframe bushes is a worthwhile mod.
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  #53  
Old 29-04-2011, 04:17 PM
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Originally Posted by UJM3 View Post
I have some Ireland Engineering subframe bushes myself to go in next week hopefully, they have been sitting inmy garage for a couple of weeks now!

I'm prepared for a bit of noise just doing it really to help preserve the subframe as I am of the same opion of some of those mentioned in this thread. Randy Forbes afaik fits this as well as part of his subframe repairs.

Will report back once I have them fitted..
Subframe bushes don't move in the same way that TA bushes do, so you'll have no problem.
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  #54  
Old 29-04-2011, 04:21 PM
UJM3 UJM3 is offline
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Subframe bushes don't move in the same way that TA bushes do, so you'll have no problem.
Ah mixed them up..

That's good to hear! this is the set I bought
http://store.nexternal.com/ireland/r...pair-p545.aspx
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  #55  
Old 29-04-2011, 06:38 PM
RST Driver RST Driver is offline
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Quote:
Originally Posted by exdos View Post
The TA bush has a metal tube insert which is clamped tight between the sides of the trailing arm brackets on the rear subframe and the poly bush fits then fits between the metal tube insert and inside the metal sleeve of trailing arm bush holder. In the case of the OEM rubber TA bush, the TA can rotate by stretching and compression of the rubber bush, but in the case of a polyurethane bush, for the TA to rotate, the metal sleeve of the TA bush holder must move over the face of the polyurethane TA bush, and/or the the bush must move around the metal sleeve insert and this creates friction. The bushes come with some silicone lubricant, but the fit of the polybushes is so tight, that there's nowhere for the lubricant to remain. Obviously, heat is generated by the frictional movement of the TA, so what little of the lubricant remains in place after fitting, soon burns away and then you get the sound of polyurethane sliding across metal creating the squeaking noise.

I tried using different lubricants and also making little reservoirs on the fitting surfaces of the polyurethane bushes, to help lubrication to remain in place, but nothing worked for long. It's such a hassle messing around with the trailing arms, that I decided to revert to OEM TA bushes and be finished with the problem once and for all. It was the only mod that I regretted doing.

You've been warned!
Quite reasonable explanation - thanks for that.

Have you tried ATE plastilube (or something like that), which is usually used for brakes? Could be worth a try since this is a long lasting high temperature lubricant.

Best regards and again thanks for saving my money ,
Phil
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  #56  
Old 29-04-2011, 07:40 PM
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Have you tried ATE plastilube (or something like that), which is usually used for brakes? Could be worth a try since this is a long lasting high temperature lubricant.

Phil
For any lubricant to work there's got to be a space for the lubricant to remain. In the case of the polyurethane TA bushes, they're slightly compressible and over-sized, so when they're inserted in the trailing arms, they obliterate all the free-space and force out any lubricant that you try to use!

I decided my life's too short to mess around anymore with these things. I should've heeded the warning of others and never bothered fitting the damned things in the first place!
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  #57  
Old 29-04-2011, 08:29 PM
RST Driver RST Driver is offline
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So they would definately need a modification. What abound putting them onto a lathe and cutting off some material in a v-shape where lubricant can remain? Is that pretty much what you tried?

Best regards,
Phil who will insert new OEM bushings.

Btw, did the Powerflex rtabs make a huge difference compared to the stock rubber ones?
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  #58  
Old 30-04-2011, 09:02 AM
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So they would definately need a modification. What abound putting them onto a lathe and cutting off some material in a v-shape where lubricant can remain? Is that pretty much what you tried?
I did something similar, but if you start cutting into the bushes, then you reduce the compressibility of them, thus you start to defeat their effectiveness of greater stiffness. Also, nobody seems to know the effect that different lubricants might have on polyurethane. I have noticed that after a few years of use, the poly bushes are now softer than they were when new, so either, they've softened with use and/or reacted with the lubricants that I've used.


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Btw, did the Powerflex rtabs make a huge difference compared to the stock rubber ones?
I fitted the polyurethane subframe bushes at the same time as poly TA bushes, but I'd already got a butt-strut on the car. They definitely made a difference to handling near the limit which I noticed at my last visit to The Ring, after I'd removed the poly TA bushes and reverted to OEM bushes. I found that on the sharp right-hander at Hohe-Acht -> Hedwigshohe I was getting a rear-wheel steer effect which I'd not had with poly bushes and my ECU data-logger shows that I was going around that bend (radius of around 46metres) at around 55mph. Otherwise, I haven't really noticed any loss of performance, only the benefit of the squeaking has gone!
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  #59  
Old 30-04-2011, 07:42 PM
RST Driver RST Driver is offline
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I've found several other complaints on bimmerforums.com about poly-bushings.
Thanks for your warning, I'll definitely install new oem rubber bushings.

Best regards,
Phil
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