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A Suspension conversation...

 
Old 10-08-2010, 11:44 PM
  #16  
Jim M.
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The biggest difference with newer cars (the BMW M3's referenced) is the electroniclly adjustable shock absorbers. Pretty much everything else is fixed AFAIK. Why can't we get an adjustable shock absorber for our cars. I'll be the first to admit I know nothing about shock absorber inner workings, but I think they are all basiclly the same except for the way they mount on the top and bottom of the shock and the overall length and travel.

We need a vendor to get a shock manufacturer to make an electrically adjustable shock for our cars. Next we need a way to control it, maybe a simple three way switch for soft, medium and hard. Or better still find a speed control to automatically change the dampening based on speed and ocillations. I'm just speaking off the cuff, but I think it doesn't need to be complicated. There's a whole bunch of people on this board smarter than me, what do you think??????????????????????????????????????????????????????????/
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Old 10-08-2010, 11:53 PM
  #17  
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Jim, modern Jaguars have air ride suspensions [as well as many other cars]... which can be made very adjustable given a variable pressure and volume of air. The equipment isn't cheap [especially the compressors], but its certainly possible...
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Old 10-08-2010, 11:54 PM
  #18  
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If you want a comfortable ride install new bilstiens with the stock springs and you car should feel very comfortable and smooth. If you stiffen the suspension the ride wil be ah.................... well how do I say this? Stiffer.
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Old 10-09-2010, 12:08 AM
  #19  
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Originally Posted by Jim M. View Post
Why can't we get an adjustable shock absorber for our cars.
There is always the Koni FSD option:
http://www.koni.com/190+M57d0acf4f16.html

Discussed in some detail in this thread starting with post #51:
https://rennlist.com/forums/928-foru...ear-apart.html
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Old 10-09-2010, 02:33 AM
  #20  
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Originally Posted by RyanPerrella View Post
Buy a BMW

at some point someone has to decide that a 42 year old car is just no longer worth trying to make contemporary.

Accept it for what it is, what are you suggesting short of altering spring and shock rates? Reengineering the suspension?

Buy a BMW, Buy a Cayman, Buy a 10 year old 911..
If I had a millions of dollars, I would have several new cars. I would still have the 928 though, and I would still be having this particular conversation, but it would be from a position of "I have had Greg Brown install three separate new suspension setups, and I am still not happy. I'll drive the bugatti back up tomorrow and see what else he has to try..."

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Old 10-09-2010, 02:34 AM
  #21  
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Originally Posted by jon928se View Post
You're not driving it fast enough.

The firm (spine shattering teeth falling out) ride of my SE on Sydneys roads becomes perfect once into 3 digit speeds.
You are of course correct on the latter, but without going into detail, very wrong on the former.
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Old 10-09-2010, 02:36 AM
  #22  
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Originally Posted by justaguy View Post
If you want a comfortable ride install new bilstiens with the stock springs and you car should feel very comfortable and smooth. If you stiffen the suspension the ride wil be ah.................... well how do I say this? Stiffer.
I put some used Bilsteins and stock springs on Leeroy. Not happy. I am thinking more about the other car, which has hypercoils and Konis. I have another full set of used Bilsteins I will address with custom valving like that one guy on here that had them revalved.
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Old 10-09-2010, 02:36 AM
  #23  
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Originally Posted by Hacker-Pschorr View Post
There is always the Koni FSD option:
http://www.koni.com/190+M57d0acf4f16.html

Discussed in some detail in this thread starting with post #51:
https://rennlist.com/forums/928-foru...ear-apart.html
I wonder truly how large an order it would take...
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Old 10-09-2010, 08:45 AM
  #24  
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I am running Konis with very stiff springs. The ride is good, but it does transmit all the expansion joints right through. If you went with hypercoils, you would probably be able to get the short soft helper springs that stack on top. You see tham on the Bilstein PS9 combos, which are unavailable for our cars.

Call Carl Faucett. He might be able to help you out.
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Old 10-09-2010, 02:15 PM
  #25  
RyanPerrella
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Originally Posted by Jim M. View Post
The biggest difference with newer cars (the BMW M3's referenced) is the electroniclly adjustable shock absorbers. Pretty much everything else is fixed AFAIK. Why can't we get an adjustable shock absorber for our cars. I'll be the first to admit I know nothing about shock absorber inner workings, but I think they are all basiclly the same except for the way they mount on the top and bottom of the shock and the overall length and travel.

We need a vendor to get a shock manufacturer to make an electrically adjustable shock for our cars. Next we need a way to control it, maybe a simple three way switch for soft, medium and hard. Or better still find a speed control to automatically change the dampening based on speed and ocillations. I'm just speaking off the cuff, but I think it doesn't need to be complicated. There's a whole bunch of people on this board smarter than me, what do you think??????????????????????????????????????????????????????????/
The adjustable suspension systems have pretty powerful computers controlling them and take measurements and make adjustments i dont even know how many times a second. Its not something you invest in and then just have hard, medium, soft. Its really ideal for a sporty street car but to try and put that system into an older car is just not going to happen. The idea is not to have shocks which can just be managed remotely between 3 firmness settings, the idea is to have the different shock rates, but you want to constantly monitor the road surface and immediately make adjustments on the fly many hundred's of times a second if need be. This requires a very large investment in hardware and an even larger investment in tuning, and then youve only just addressed the dampers on the car, what about every other component now?

BMW used to have multiple valving inside their EDC dampers (90's era technology) and this led to a basic 3 stage setting for those shocks. But now the fun thing to do is go with the magnetorheological dampers which are oil filled but have tiny magnetic nano particles in them which when charged can create differing viscosities and translates into vastly more variability than can the earlier multi valved shocks. I would probably say that between a maximum and a minimum they are infinitely adjustable. I believe this technology is patented to a US company like Delco or someone but Ferrari uses this in all their cars now. Acura runs a commercial for their RDX or MDX or some crossover/wagon thing that has a graphical demonstration of how the oil can be manipulated.

But all of these components are controlled by computers and the sensors are all highly integrated throughout the chassis from yaw and pitch and steering angle and speed and who knows what else. The more things you were monitoring the more information you would have to make the correct adjustments but this only multiplies the problems you then have of what to do with all that information.

Clearly this is not really an option for the 928 unless you really did want to drive yourself nuts. Even if you could install it you would never have the budget to tune it properly. I think every car company that uses these things spends upwards of 2 years just tuning the things.

Im not sure how Porsches PASM dampers alter their rates, I believe its some sort of valving manipulation though where the valve disc rotates in a certain manner to open and close off chambers and alter the flow of oil in the damper. They have yet to hop on the magnetic shock train. But most regard the PASM to be a good system and you can now even buy aftermarket dampers which take advantage of the system and not just eliminate it.


Originally Posted by jleidel View Post
Jim, modern Jaguars have air ride suspensions [as well as many other cars]... which can be made very adjustable given a variable pressure and volume of air. The equipment isn't cheap [especially the compressors], but its certainly possible...
You can put airbag suspension in all sorts of 60's and 70's muscle cars, and while its an adjustable suspension your really only adjusting the spring rates the dampers would have to be altered some other way. But the whole air shock wouldn't be much use in my eyes because it takes a few seconds or possibly a dozen seconds to adjust the spring pressure and if you wanted something comparable to the E92 M3 this would mean rates on each corner inflating and deflating hundreds of times a second, something that system just cannot handle unless you carried an air supply the size of a blimp.

The air springs are typically installed because you can alter ride height and are mostly installed for cosmetics although Air-Ride would have you believe that they can make a huge difference in the handling department as well, which maybe true considering what they are starting with, anything is an improvement. For a sports car however, not ideal. And to the Jaguar reference, air springs do have an application in luxo sedans because the adjustable springs allow the chassis to sit level with differing loads and the air spring is a better ride in the rear than the steel coil. Mercedes used to have air on 4 corners but I believe now on the applications that call for air springs, the fronts are now steel and only the rears are air springs.

________________________________________________________________________ _____________

Brendan, like I asked in the first post, what kind of responses are you looking for short of the common Bilstein vs. koni vs. stock vs. eibach debate which is where this discussion has lead?

I'll pose a question in response to Rob's mention that the car handles progressively worse the lower it goes and suggests the 170mm setting which is higher than i like just from the position that the car looks better closer to the ground. How do you alter the way the suspension reacts with lowered cars short of changing the pickup points? I dont think you can?

I had thought of producing adjustable (in length) rear suspension upper links but aside from adjusting rear camber I dont know what real benefit you could get from them, thats an easy enough thing to reproduce but I havent thought of what reason it would serve other than to sell everyone more parts they dont really need?
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Old 10-09-2010, 02:58 PM
  #26  
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Originally Posted by WallyP View Post
"When you increase the sway bar stiffness, and increase the spring rates, and tighten up the shocks,... "

And install short, stiff 17"/18"/19" tires...

With stock suspension, wheels and tires in good condition, they are pretty darn comfortable.
That's been my impression. I've ridden in a lot of 928s and many of them were smooth over bumps and joints but still predictable and stable when pushed. That's the way my car was when I got it at 72K miles. It took a big dump in handling and comfort when I replaced the original Boge reds with Konis and Eibach, is considerably better now with Bilsteins and stock springs.
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Old 10-11-2010, 04:23 AM
  #27  
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If you put on higher rate springs and do not revalve the shocks then the ride will be worse.
The compression needs to be reduced, rebound increased.
Winding up the Koni adjuster will just make it worse.
So, if you purchase a hypercoil set up, you need to complete the job and get Koni to revalve the shocks.

Increasing the anti roll bars will give you that side to side jerk, go for a ride in a SUV like an X5 [our 02 model at least] over one bump. The wheel doesn't absorb much but you get rocked, I hate it!

The small helper spring is fully compressed when installed. Its just there to stop the spring falling out when the wheel leaves the ground, jumping etc! You would need a helper only at high rates as the main spring is shorter. I know as I have them on my shocks....

I believe that early Konis had an incorrect valve that made them very harsh.

You can also add some car audio sound deadening to help remove the road noise, works a treat
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Old 10-11-2010, 04:35 AM
  #28  
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Originally Posted by blazing928 View Post
So, if you purchase a hypercoil set up, you need to complete the job and get Koni to revalve the shocks.
Or get Bilstein to revalve their shocks to your specifications.

Ive never been a fan of Koni when a product like Bilstein is also available. But YMMV
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Old 10-11-2010, 12:58 PM
  #29  
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Originally Posted by RyanPerrella View Post

Brendan, like I asked in the first post, what kind of responses are you looking for short of the common Bilstein vs. koni vs. stock vs. eibach debate which is where this discussion has lead?
I know that we have several people here with more technical suspension experience than the average bear. I'd like to hear from them - experiences, opinions, etc.

I have driven on Bilsteins - I have always felt they were very jumpy - the car easily gets unsettled - I believe that any shock that the 928 will get for install will be a compromise unless it is valved specifically for what you have on your car. Corner weighting also seems quite important for shorter wheel base cars like ours. I don't use Eibachs normally. The reason I installed Konis on the 78 project and they still sit there, installed is because that was what as available in 2003 when I bought them from Devek... But obviously things change. I have a used set of Bilsteins that I will probably send to Poway, CA (not 10 miles from here) for Bilstein to revalve. If you recall, I have the machine designs for lower and upper spring hats to use Hypercoils on a bilstein tube. But again - they have always been very bouncy - even with stock springs.


Originally Posted by RyanPerrella View Post
How do you alter the way the suspension reacts with lowered cars short of changing the pickup points? I dont think you can?
The bottom pick up point could be shimmed a bit if that made any difference. Or you could even shave the body area a bit there where the gussets are for the front and rear lower arm brackets. The upper arm COULD be relocated in or out by the same metal removal. I don't know about moving it up or down, other than widening the hole and welding in a new bushing there - you could probably get 5mm - but then you would have to change the tang-bracket on the K-member.

But doing that with no idea of what it would do to the dynamics of the car could be a waste of time.

Originally Posted by RyanPerrella View Post
I had thought of producing adjustable (in length) rear suspension upper links but aside from adjusting rear camber I dont know what real benefit you could get from them, thats an easy enough thing to reproduce but I havent thought of what reason it would serve other than to sell everyone more parts they dont really need?
We need those upper rear arms adjustable for several reasons I may not be able to explain well here. I made some, but mine are not as pretty as Mike Simard's. But they do exist, and many cars could benefit.

As you adjust the rear suspension camber and tow, the wheel movement changes - the arc it takes up and down. From what I read, if you make the top link adjustable, you can better control what arc that wheel takes as it goes up and down when you are adjusting for tow and camber. The bottom link at the lower a-arm towards the center of the car is where Camber is controlled. If you wanted to make camber a certain number, but keep the track at a certain other number, you could use those top arms with adjustments to do that.

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Old 10-11-2010, 03:32 PM
  #30  
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Hmmmmmmmmmmmmmm.................

I am still happy with my 600/400 set up with revalved Bilsteins. It feels stiff until you start going fast, then it feels perfect. It of course is pretty harsh on pot holes, expansion joints, etc.

Like Jim M said, it would be nice to have cockpit adjustable dampening.... but it wouldn't help stiff springs. All you would be looking for is lighter compression dampening for normal driving and then heavier for faster driving. The rebound should be the same all the time.

For the money, you can't beat the revalved Bilsteins. You have to accept one ride though with some compromises.

just for the record, my revalving specs at Bilstein (for the 600/400 Hypercoil springs) are for stiffer low speed compression and rebound. Low speed compression is for cornering, braking, dips in the road. High speed compression would be bumps and pot holes, expansion joints.
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