PSS-9 spring top hat question
03-13-2003, 10:33 PM
#1
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PSS-9 spring top hat question
I am going to install a PSS-9 kit in my car and after searching the archives I am not certain of how the Bilstein supplied top hat fits into the stock rear mount area on the 993. Is it possible to use the stock top spring hat with the spring supplied in the PSS-9 kit and just bolt the rear Bilstein shock top through it and just mount it back as if it were original. All the talk about the Bilstein not riding on much of the rear mount has me worried about this kit. It is on order thru Gert and will be here in about two weeks. I need some help understanding this as I only have looked at pictures of this kit and have not taken my rear shocks/springs apart to know exactly what I am talking about. 
03-13-2003, 10:40 PM
#2
Steve at Rennsport has a neat solution that integrates a stock mount, but many of us have done monoball mounts. I just installed the ones from The Racer's Group. Check it out!
03-13-2003, 11:42 PM
#4
Edited by Brian on 3/14/2003
I deleted my original comments as I don't want to confuse the issues any further and have this thread go off on a tangent. Jim's analysis of the OEM setup regarding where the springs mounts vs. where the PSS-9 system springs mount is correct.
Jim and Steve comments are more appropriate than my original rant about this topic.
I deleted my original comments as I don't want to confuse the issues any further and have this thread go off on a tangent. Jim's analysis of the OEM setup regarding where the springs mounts vs. where the PSS-9 system springs mount is correct.
Jim and Steve comments are more appropriate than my original rant about this topic.
03-14-2003, 01:07 AM
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Brian:
A little "flamo" your way... I sure hope that you have PSS-9's yourself, the first hand knowledge of their setup and have worked through this issue in some fashion in order to back the very "confident" statements made above.
As the person who designed the upper spring hat Steve W. at Rennsport is now offering, I can say from first hand knowledge that the issue is not one of simply worrying about upper perch failure. (I know past threads got off on that direction and that is really too bad.)
The real issue, for those of us who would prefer to not use monoballs with PSS-9's on our 993's, is one of correctly placing the rear spring load onto the chassis.
The OEM rear shock mount is intended to isolate the shock absorber motion, not support the vehicle weight. When the corner weight of the car is added, the mount deflects with an un-damped spring rate of the now weight laden rubber section. This adds a "third spring" into the coilover. For those curious, the mount's deflection under load is about 1/2 of an inch.
FWIW, I agree completely that given the stout construction of the mount it could likely take the corner weight and not fail. However, what about the un-damped motion ???
The undamped motion question got uncovered for me while I was attempting to "dial in" my own PSS-9's. I could not find good reason for the car's uneasy rear end feeling while navigating long, some what bumpy sweepers. Shock settings dod not seem to make a difference. This unsettled feeling was something new since installing the PSS-9's and could only relate to their installation.
After eliminating several possibilities such as sway bar bind, shocks working corectly, etc., I noticed the deflection of the rear mount as the car's weight came down on the suspension. I went ahead and measured the deflection and realized that this motion would be un-damped by the shock absorber. After debating the possible fix via the addition of the rear monoball uppers, I decided against it. Instead, I went ahead with another idea of getting the spring load onto the the chassis as Porsche did with the OEM rear strut. I prototyped the the fix and tested it. (btw, Steve W. was a great help getting the idea to reality. Many reality check phone calls !) Upon istallation of the new hats with everything else set the same, my observed handling issue vanished.
After having gone through the DIY on the PSS-9's with considerable help from Steve W., I provided Steve the design to give folks yet another option !
All of this story told... Are these hats for everyone...NO... Put simply. If you don't get it, don't use 'em.
RC: If you would like any more detail, feel free to PM me.
Regards
A little "flamo" your way... I sure hope that you have PSS-9's yourself, the first hand knowledge of their setup and have worked through this issue in some fashion in order to back the very "confident" statements made above.
As the person who designed the upper spring hat Steve W. at Rennsport is now offering, I can say from first hand knowledge that the issue is not one of simply worrying about upper perch failure. (I know past threads got off on that direction and that is really too bad.)
The real issue, for those of us who would prefer to not use monoballs with PSS-9's on our 993's, is one of correctly placing the rear spring load onto the chassis.
The OEM rear shock mount is intended to isolate the shock absorber motion, not support the vehicle weight. When the corner weight of the car is added, the mount deflects with an un-damped spring rate of the now weight laden rubber section. This adds a "third spring" into the coilover. For those curious, the mount's deflection under load is about 1/2 of an inch.
FWIW, I agree completely that given the stout construction of the mount it could likely take the corner weight and not fail. However, what about the un-damped motion ???
The undamped motion question got uncovered for me while I was attempting to "dial in" my own PSS-9's. I could not find good reason for the car's uneasy rear end feeling while navigating long, some what bumpy sweepers. Shock settings dod not seem to make a difference. This unsettled feeling was something new since installing the PSS-9's and could only relate to their installation.
After eliminating several possibilities such as sway bar bind, shocks working corectly, etc., I noticed the deflection of the rear mount as the car's weight came down on the suspension. I went ahead and measured the deflection and realized that this motion would be un-damped by the shock absorber. After debating the possible fix via the addition of the rear monoball uppers, I decided against it. Instead, I went ahead with another idea of getting the spring load onto the the chassis as Porsche did with the OEM rear strut. I prototyped the the fix and tested it. (btw, Steve W. was a great help getting the idea to reality. Many reality check phone calls !) Upon istallation of the new hats with everything else set the same, my observed handling issue vanished.
After having gone through the DIY on the PSS-9's with considerable help from Steve W., I provided Steve the design to give folks yet another option !
All of this story told... Are these hats for everyone...NO... Put simply. If you don't get it, don't use 'em.
RC: If you would like any more detail, feel free to PM me.
Regards
03-14-2003, 05:13 AM
#7
RL Technical Advisor
Hi Brian:
LOL,........Mr. Morton spoke eloquently on this subject and I've little to add (for once, eh?)
There is no real harm in using the PSS-9 upper spring hat with the OEM rubber mount, but the car will not "feel" right when you push it.
In a nutshell, the excess deflection of the center of the rubber mount makes the car feel "squishy", for lack of a descriptive technical term,...
The custom rear spring perch kit that Jim designed offers some of the benefits of a monoball without any noise or vibration issues. These kinds of things are subjective in nature and some folks elect to run camberplates/monoballs on the street but generally speaking, I do not recommend them except for race cars.
Randy; You may see these for yourself on the 993 page of our website and I can also e-mail several more pics of this for your perusal.
LOL,........Mr. Morton spoke eloquently on this subject and I've little to add (for once, eh?)
There is no real harm in using the PSS-9 upper spring hat with the OEM rubber mount, but the car will not "feel" right when you push it.
In a nutshell, the excess deflection of the center of the rubber mount makes the car feel "squishy", for lack of a descriptive technical term,...
The custom rear spring perch kit that Jim designed offers some of the benefits of a monoball without any noise or vibration issues. These kinds of things are subjective in nature and some folks elect to run camberplates/monoballs on the street but generally speaking, I do not recommend them except for race cars.
Randy; You may see these for yourself on the 993 page of our website and I can also e-mail several more pics of this for your perusal.
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03-14-2003, 10:20 AM
#8
I have edited my original comment so not to allow this thread to go off on a tangent regarding the hat failure as this was the way I interpreted the question.
I do have the PSS-9's.
The hats that Steve is selling sound impressive and serve a better function than the one I was under the impression they originally were designed to cure. I thought they came about merely as a result of not liking the lip contact point on the PSS-9 hat and fearing it would damage the "original" hat. I stand corrected there is more to them than I was aware and they seem to be a beneficial upgrade from the standard PSS-9 hats.
Now Steve how much are these hats?
I do have the PSS-9's.
The hats that Steve is selling sound impressive and serve a better function than the one I was under the impression they originally were designed to cure. I thought they came about merely as a result of not liking the lip contact point on the PSS-9 hat and fearing it would damage the "original" hat. I stand corrected there is more to them than I was aware and they seem to be a beneficial upgrade from the standard PSS-9 hats.
Now Steve how much are these hats?
03-14-2003, 11:21 PM
#9
RL Technical Advisor
Hi Brian:
LOL,....I too, think these custom spring perches are pretty neat although I must admit to being somewhat biased,.....
Since I try not do any business on the Forums or Lists, I'll PM you with pricing.
LOL,....I too, think these custom spring perches are pretty neat although I must admit to being somewhat biased,.....
Since I try not do any business on the Forums or Lists, I'll PM you with pricing.
03-15-2003, 11:33 AM
#10
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To All,
I just completed my PSS-9 (w/Turbo Sways) install last week, and I love the way it has transformed the car! It now handles the way a Porsche should!
I too had read about the rear spring perch issue, but figured that some guys were just being AR (we p-car types seem to lean in that direction). However, when I got my rear struts apart and saw the way the Bilstein PSS-9 strut mated with the factory perch I decided there was NO WAY I was going to bolt me car back together that way! I called Steve and he overnighted a pair of his spring perches to me.
Money well spent!!!! (no affiliation, yada, yada...) The new "hats" distribute the spring load onto the chassis the way it should be. If you're considering a PSS-9, buy the new spring perches! They are very well designed and executed!
Cheers! <img border="0" alt="[cheers]" title="" src="graemlins/beerchug.gif" />
I just completed my PSS-9 (w/Turbo Sways) install last week, and I love the way it has transformed the car! It now handles the way a Porsche should!
I too had read about the rear spring perch issue, but figured that some guys were just being AR (we p-car types seem to lean in that direction). However, when I got my rear struts apart and saw the way the Bilstein PSS-9 strut mated with the factory perch I decided there was NO WAY I was going to bolt me car back together that way! I called Steve and he overnighted a pair of his spring perches to me.
Money well spent!!!! (no affiliation, yada, yada...) The new "hats" distribute the spring load onto the chassis the way it should be. If you're considering a PSS-9, buy the new spring perches! They are very well designed and executed!
Cheers! <img border="0" alt="[cheers]" title="" src="graemlins/beerchug.gif" />
03-15-2003, 12:30 PM
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I'll chime in -- I'd gone ahead & ordered the PSS9s and Morton spring perches based on the conversations here. After seeing the contact area w. the Bilstein perch, I was very happy that I had an alternative perch in hand & ready to use.
03-15-2003, 01:01 PM
#12
Thanks Steve
03-15-2003, 01:51 PM
#13
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I'll chime in too. Just did the Pss-9 switch. I went with Jim's hats, and have been very favorably impressed. I spoke with both Jim and Steve and was just blown away by their knowledge on this issue. I would bet that the ride is similar to monoballs but perhaps not quite so harsh.
Note: This is one killer mod. It'll feel like a different car. In addition, it's a real pleasure to do business with people like Steve and Jim.
Cheers,
Chris
Note: This is one killer mod. It'll feel like a different car. In addition, it's a real pleasure to do business with people like Steve and Jim.
Cheers,
Chris
03-16-2003, 12:13 AM
#14
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Everyone...
Thanks for your replys and I too talked to both Jim and Steve and after getting the full story I also have the custom spring perches on order from Steve. There has been a lot of discussion on this topic and I hope this clears up the proper way to mount the PSS-9 kit on a 993. To spend this kind of money for an expected handeling boost and not mate the rear springs properly just doesn't make sense. I am looking forward to the addition of this kit on my car. <img border="0" alt="[cheers]" title="" src="graemlins/beerchug.gif" />
Thanks for your replys and I too talked to both Jim and Steve and after getting the full story I also have the custom spring perches on order from Steve. There has been a lot of discussion on this topic and I hope this clears up the proper way to mount the PSS-9 kit on a 993. To spend this kind of money for an expected handeling boost and not mate the rear springs properly just doesn't make sense. I am looking forward to the addition of this kit on my car. <img border="0" alt="[cheers]" title="" src="graemlins/beerchug.gif" />
