Subframe mounts - OEM or Poly?

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BladeRunner919
Joined: Fri 17 Feb, 2012 20:18
Posts: 2225

  Z3 roadster 1.9

Subframe mounts - OEM or Poly?

Post by BladeRunner919 »

Any opinions on Powerflex vs OEM for the subframe mounts on a Z3?
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Captain
Joined: Thu 28 Jun, 2012 06:43
Posts: 520

  Z3 roadster 2.8
Location: Durban

Re: Subframe mounts - OEM or Poly?

Post by Captain »

Read a lot of good things about them, haven't tried them myself, be good to hear from those that have them installed.

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Gazza
Joined: Tue 04 Oct, 2005 20:58
Posts: 9521

  M roadster S54
Location: Romford Essex

Re: Subframe mounts - OEM or Poly?

Post by Gazza »

Personally I would stay with OEM, reason being I have known failures that have occured using Poly bushes which (may have) caused a strut rod to fail (not on a BMW) due to the restricted movement using Poly over Rubber OEM bushes.

I have no proof just incase those Techie Engineers here wish to slam my personal thoughts on the subject :)
Gazza

"Understeer is when you hit the wall with the front of the car, oversteer is when you hit the wall with the rear of the car. Horsepower is how fast you hit the wall and torque is how far you take the wall with you"

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Del
Joined: Sat 19 Nov, 2011 18:35
Posts: 2136

  Z3 roadster 1.9

Re: Subframe mounts - OEM or Poly?

Post by Del »

I tend to agree with Gazza I would stick to OEM standard for a normal road car. The rear OE bushes are not a known fault area like the front wishbone (rear) bushes. They are therefore, a known quantity and have served their purpose well for 10+ years. I have picked up a lot of feedback that Poly ones can provide a harsh and squeaky ride when fitted at the back – the squeakiness is only addressed by applying certain lubricant.
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BladeRunner919
Joined: Fri 17 Feb, 2012 20:18
Posts: 2225

  Z3 roadster 1.9

Re: Subframe mounts - OEM or Poly?

Post by BladeRunner919 »

I thought the squeaking was the trailing arm bushes, which do undergo a rotational movement. The subframe mounts shouldn't squeak. The reasons for thinking Powerflex are that they will be easier to install, plus the oem ones have two voids in them (which some people plug with plastic inserts) so can give some movement.

The main reason is the ease, however, as I'm not planning on racing the car and it is only a 1.9 after all.
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Gazza
Joined: Tue 04 Oct, 2005 20:58
Posts: 9521

  M roadster S54
Location: Romford Essex

Re: Subframe mounts - OEM or Poly?

Post by Gazza »

BladeRunner919 wrote:I thought the squeaking was the trailing arm bushes, which do undergo a rotational movement. The subframe mounts shouldn't squeak. The reasons for thinking Powerflex are that they will be easier to install, plus the oem ones have two voids in them (which some people plug with plastic inserts) so can give some movement.

The main reason is the ease, however, as I'm not planning on racing the car and it is only a 1.9 after all.
I believe the plastic inserts are to take up the slack in an old bush, Mike Fishwick did a DIY insert install.
Gazza

"Understeer is when you hit the wall with the front of the car, oversteer is when you hit the wall with the rear of the car. Horsepower is how fast you hit the wall and torque is how far you take the wall with you"

Z3 S54 M roadster Image, BMW Z1, BMW M3 CSL, Z4M Coupe
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Deano1712
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Joined: Sat 05 Aug, 2006 12:56
Posts: 1396

  M roadster S50
Location: Leeds

Re: Subframe mounts - OEM or Poly?

Post by Deano1712 »

If you get chance to change the bushes I recommend you do it. You will notice a more stable and predictable rear suspension response. The fact that your car is a 1.9 doesnt come into it. The subframe bushes dont squeek - that is associated with poly trailing arm bushes, as you say.
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siwilson
Joined: Fri 19 Jun, 2009 09:54
Posts: 790

  M roadster S54
Location: Horley

Re: Subframe mounts - OEM or Poly?

Post by siwilson »

Deano1712 wrote:If you get chance to change the bushes I recommend you do it. You will notice a more stable and predictable rear suspension response. The fact that your car is a 1.9 doesnt come into it. The subframe bushes dont squeek - that is associated with poly trailing arm bushes, as you say.
+1. I have these from Ireland engineering

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Big improvement.
2001 M roadster S54 Laguna Seca Blue
siwilson
Joined: Fri 19 Jun, 2009 09:54
Posts: 790

  M roadster S54
Location: Horley

Re: Subframe mounts - OEM or Poly?

Post by siwilson »

Actually, the one area I think you need to keep OEM is the bush in the diff mount. it is the movement of that bush that does most of the boot floor damage and a stiffer bush there will only maker it worse.

The stiffer subframe bushes actually help reduce boot floor damage by preventing the subframe from moving around or twisting as much. The grooves you see on the Ireland bush above just allow it to slide into the subframe. There are 4 locating domes in the subframe recess. Other than that it down not move much at all, but due to the urethane does 'give' a bit.

IMO bush choices should be as follows

Front radius arm (lollipop) = new OEM, but from the ///M on all models
Front ARB mounts = Urethane
Rear ARB mounts = Urethane
Rear Subframe mounts = Urethane
Diff mount = OEM
Rear trailing arm bushes = new OEM
2001 M roadster S54 Laguna Seca Blue
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