New Performance Suspension Bushings
11-13-2018, 08:20 PM
#16
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Let's wait till a few more folks fit them, I will fit them soon and and add to this discussion, the other matter I would disagree with the spring rate comment, I would say it's not spring rate but damping rate. The reason is that the bushes resist movement, as such damp the wheel assembly.
11-13-2018, 08:40 PM
#17
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Let's wait till a few more folks fit them, I will fit them soon and and add to this discussion, the other matter I would disagree with the spring rate comment, I would say it's not spring rate but damping rate. The reason is that the bushes resist movement, as such damp the wheel assembly.
Will waiting a few months change the physics of how the OEM bushes were designed, and how these were not designed to be the same thing?
I think this has been an actual known thing for a # of years ago. Thats why the LCA bushes are so LARGE, they are a large torsion spring.
You don't believe that these are meant to provide spring rate supplement to the suspension?
Damping is the shock's job...not a spring's job...if you meant NVH, yes, they will damp road vibrations some. Urethane bushes dampen much less, but better than brass bushing I spose.
The OEM design is also zero friction, poly replacements operate ON friction, must rotate, and have a wear rate.
To each their own, but its not for good reason these are not in the top 100 things to do to your 928.
11-13-2018, 09:08 PM
#18
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Will waiting a few months change the physics of how the OEM bushes were designed, and how these were not designed to be the same thing?
I think this has been an actual known thing for a # of years ago. Thats why the LCA bushes are so LARGE, they are a large torsion spring.
You don't believe that these are meant to provide spring rate supplement to the suspension?
Damping is the shock's job...not a spring's job...if you meant NVH, yes, they will damp road vibrations some. Urethane bushes dampen much less, but better than brass bushing I spose.
The OEM design is also zero friction, poly replacements operate ON friction, must rotate, and have a wear rate.
To each their own, but its not for good reason these are not in the top 100 things to do to your 928.
I think this has been an actual known thing for a # of years ago. Thats why the LCA bushes are so LARGE, they are a large torsion spring.
You don't believe that these are meant to provide spring rate supplement to the suspension?
Damping is the shock's job...not a spring's job...if you meant NVH, yes, they will damp road vibrations some. Urethane bushes dampen much less, but better than brass bushing I spose.
The OEM design is also zero friction, poly replacements operate ON friction, must rotate, and have a wear rate.
To each their own, but its not for good reason these are not in the top 100 things to do to your 928.
11-13-2018, 09:24 PM
#19
Three Wheelin'
I have just fitted a full Powerflex set up in the front. In fact every front bush is now poly. I have now had four 928 guys, including the mechanic drive it and they all said the same thing. Amazing. The ride is exceptional. The steering absolutely pin sharp. There is no way I'd go back to rubber now. Can't wait to do the rear.
11-13-2018, 09:29 PM
#20
Three Wheelin'
Answer to your first question is no. I acknowledge they are a store of energy when moved. So are gas filled dampers. We agree on the NVH issue but bushes should never be springs, I think you are conflating resistance to movement with friction. The wear rate should be very low as long as they are kept lubricated. As mentioned I think lubrication every three years is fair and consistent with the manufacturer's experience. The bushes have a life time warranty so I wouldn't expect a high wear rate. The bushes (aside from NVH in a road car) should just provide an accurate and controlled movement of the arm.
11-14-2018, 10:45 AM
#21
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That you have positive feedback is good news- as to how long they last at that level remains to be seen. I have a feeling they will do well in that regard.
I do not understand Greg's comment about lubrication- the only lubrication I am aware of is that needed to get the bushes into the arms initially. There are no parts that move and the bushes rely on flexure [hence the name Powerflex] That they offer two types- stiff and stiffer is interesting but any notion that such is a bad thing is a bit like saying different suspensions do not work and that would be utter nonsense- they do work in different ways- some improvement handling wise at the expense of comfort- no free lunches! If the arms put up more resistance to torsion to achieve less distortion under load then logic suggests they need more spring force to counter it [already have that!].
Sticking with what Porsche offered originally for sure causes no harm but to write off a product with potential for improvement without trying it is not exactly moving forwards especially when there is no factory replacement part for the Weissach bushing.
11-14-2018, 11:51 AM
#22
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Fred you bring up an interesting point. Who does offer a replacement for the Weissach bushing?
For that matter, is there any single company that offers a complete set of replacement bushing, both front and rear?
Asking because I'm getting close, in the restoration projects lists, to doing the complete replacements.
Paul
For that matter, is there any single company that offers a complete set of replacement bushing, both front and rear?
Asking because I'm getting close, in the restoration projects lists, to doing the complete replacements.
Paul
11-14-2018, 12:52 PM
#23
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That being said I am not aware of these items having failed or worn out but presumably they have a finite life expectancy be it through wear or aging of the rubber.
11-14-2018, 02:25 PM
#24
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Mark Anderson sells exchange arms that are rebuilt. Sometimes there is listings on German eBay for the bushings but how to fit? Maybe two part urethane?
11-14-2018, 02:32 PM
#25
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Your mechanic's comment is nonsense but that is not to say the stock items cannot be improved on as I hope the Powerflex bushes might be. Perhaps all he has experienced are tired original items. Even then the lower arm bushes seem surprisingly resilient upon aging.
That you have positive feedback is good news- as to how long they last at that level remains to be seen. I have a feeling they will do well in that regard.
I do not understand Greg's comment about lubrication- the only lubrication I am aware of is that needed to get the bushes into the arms initially. There are no parts that move and the bushes rely on flexure [hence the name Powerflex] That they offer two types- stiff and stiffer is interesting but any notion that such is a bad thing is a bit like saying different suspensions do not work and that would be utter nonsense- they do work in different ways- some improvement handling wise at the expense of comfort- no free lunches! If the arms put up more resistance to torsion to achieve less distortion under load then logic suggests they need more spring force to counter it [already have that!].
Sticking with what Porsche offered originally for sure causes no harm but to write off a product with potential for improvement without trying it is not exactly moving forwards especially when there is no factory replacement part for the Weissach bushing.
That you have positive feedback is good news- as to how long they last at that level remains to be seen. I have a feeling they will do well in that regard.
I do not understand Greg's comment about lubrication- the only lubrication I am aware of is that needed to get the bushes into the arms initially. There are no parts that move and the bushes rely on flexure [hence the name Powerflex] That they offer two types- stiff and stiffer is interesting but any notion that such is a bad thing is a bit like saying different suspensions do not work and that would be utter nonsense- they do work in different ways- some improvement handling wise at the expense of comfort- no free lunches! If the arms put up more resistance to torsion to achieve less distortion under load then logic suggests they need more spring force to counter it [already have that!].
Sticking with what Porsche offered originally for sure causes no harm but to write off a product with potential for improvement without trying it is not exactly moving forwards especially when there is no factory replacement part for the Weissach bushing.
The bushings do move, they work like a bearing. This is the reason for the reduced friction. There is no binding with these parts. So the outer part of the three part assembly (urethane) slides over the stainless sleeve. The reason I say "may need to re-lubed" is that the grease can dry out and also it can just work it's way out of the grooving in the bushing over time with use.
11-14-2018, 03:38 PM
#26
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G'day Fred,
The bushings do move, they work like a bearing. This is the reason for the reduced friction. There is no binding with these parts. So the outer part of the three part assembly (urethane) slides over the stainless sleeve. The reason I say "may need to re-lubed" is that the grease can dry out and also it can just work it's way out of the grooving in the bushing over time with use.
Trust the shrimps are doing well on barbie mate!
Your perception of how the system works is somewhat different to mine [which may turn out to be incorrect].
As I visualise such a system, either the urethane flexes to achieve rotation as per the stock item or it slips over the metal surface with little to no resistance. If the latter case with differential movement were the case I find it difficult to believe the material could survive yet alone retain geometric compliance. The urethane has some interesting mechanical properties but as I am aware, lubrication is not one of them.
In your discussions with Powerflex did you discuss the "modus operandi" with them? An interesting subject matter for discussion irrespective of the outcome.
Regards
Fred
11-14-2018, 03:58 PM
#27
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Hi Greg,
Trust the shrimps are doing well on barbie mate!
Your perception of how the system works is somewhat different to mine [which may turn out to be incorrect].
As I visualise such a system, either the urethane flexes to achieve rotation as per the stock item or it slips over the metal surface with little to no resistance. If the latter case with differential movement were the case I find it difficult to believe the material could survive yet alone retain geometric compliance. The urethane has some interesting mechanical properties but as I am aware, lubrication is not one of them.
In your discussions with Powerflex did you discuss the "modus operandi" with them? An interesting subject matter for discussion irrespective of the outcome.
Regards
Fred
Trust the shrimps are doing well on barbie mate!
Your perception of how the system works is somewhat different to mine [which may turn out to be incorrect].
As I visualise such a system, either the urethane flexes to achieve rotation as per the stock item or it slips over the metal surface with little to no resistance. If the latter case with differential movement were the case I find it difficult to believe the material could survive yet alone retain geometric compliance. The urethane has some interesting mechanical properties but as I am aware, lubrication is not one of them.
In your discussions with Powerflex did you discuss the "modus operandi" with them? An interesting subject matter for discussion irrespective of the outcome.
Regards
Fred
11-14-2018, 04:23 PM
#28
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You have been watching Paul Hogan's American TV ads, in fact we don't use the word shrimp, it's a prawn here. Anyway, it's the later scenario you describe. So why we have three pieces is the first urethane part pushes over the casting which is too rough to be used as a sliding surface. They then fit a stainless sleeve over that piece and it's a tight fit not designed to move or rotate. The outer surface of the stainless is the bearing surface. The outer bush is pushed or clamped in the housing and doesn't rotate or move. The inner part of that bush is knurled and has recesses for grease. This is where the work is done.
11-14-2018, 04:29 PM
#29
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11-14-2018, 05:57 PM
#30
Three Wheelin'
Your mechanic's comment is nonsense but that is not to say the stock items cannot be improved on as I hope the Powerflex bushes might be. Perhaps all he has experienced are tired original items. Even then the lower arm bushes seem surprisingly resilient upon aging.
That you have positive feedback is good news- as to how long they last at that level remains to be seen. I have a feeling they will do well in that regard.
I do not understand Greg's comment about lubrication- the only lubrication I am aware of is that needed to get the bushes into the arms initially. There are no parts that move and the bushes rely on flexure [hence the name Powerflex] That they offer two types- stiff and stiffer is interesting but any notion that such is a bad thing is a bit like saying different suspensions do not work and that would be utter nonsense- they do work in different ways- some improvement handling wise at the expense of comfort- no free lunches! If the arms put up more resistance to torsion to achieve less distortion under load then logic suggests they need more spring force to counter it [already have that!].
Sticking with what Porsche offered originally for sure causes no harm but to write off a product with potential for improvement without trying it is not exactly moving forwards especially when there is no factory replacement part for the Weissach bushing.
That you have positive feedback is good news- as to how long they last at that level remains to be seen. I have a feeling they will do well in that regard.
I do not understand Greg's comment about lubrication- the only lubrication I am aware of is that needed to get the bushes into the arms initially. There are no parts that move and the bushes rely on flexure [hence the name Powerflex] That they offer two types- stiff and stiffer is interesting but any notion that such is a bad thing is a bit like saying different suspensions do not work and that would be utter nonsense- they do work in different ways- some improvement handling wise at the expense of comfort- no free lunches! If the arms put up more resistance to torsion to achieve less distortion under load then logic suggests they need more spring force to counter it [already have that!].
Sticking with what Porsche offered originally for sure causes no harm but to write off a product with potential for improvement without trying it is not exactly moving forwards especially when there is no factory replacement part for the Weissach bushing.