My crusade for a "better" suspension set up
08-30-2010, 11:43 AM
#1
Registered User
Thread Starter
My crusade for a "better" suspension set up
For the past few months ive been looking to upgrade my suspension. I currenty have koni yellows and ground control springs with 350f and 450r rates. my konis started leaking at the track on day when i went to soften the rear. i tightened it back up to stop it from leaking. this event was the catalyst to my quest. i never really questioned the set up bc it was on the car when i bought it so that department was always considered "done" in my mind. now i want to get something else thats a "clean slate" where i can learn to suspension tune myself. Its literally all i think about now. My girlfriend wakes up to me saying tire sizes and spring rates in my sleep (its that bad).
Just to give you a general idea, its a DD with occasional track use, but i do go on spirited drives almost every weekend.
i came across a great deal on bilstein PSS9s and from my understanding they are great when it comes to dampening but the spring rates are a bit soft. a big deal to me is body roll. i cant stand it and i'm worried the weak spring rates are gonna bring it back. the GCs give me almost zero body roll. i'm not concerned with slam ability. i didnt by advans and RE-11s just to add a non functioning set up so i can drag frame everywhere. although my prefered ride height would be equal to that of diez's car. neither 4x4 or dumped but a good functional height.
i almost want to keep the konis and swap the front springs to the rear to go softer in the rear but seeing as my car is my DD i cant have down time soi wouldnt be able to send off my only struts to be re valved so it would need to be a direct swap.
either way, any and all feedback is welcomed. thanks
Just to give you a general idea, its a DD with occasional track use, but i do go on spirited drives almost every weekend.
i came across a great deal on bilstein PSS9s and from my understanding they are great when it comes to dampening but the spring rates are a bit soft. a big deal to me is body roll. i cant stand it and i'm worried the weak spring rates are gonna bring it back. the GCs give me almost zero body roll. i'm not concerned with slam ability. i didnt by advans and RE-11s just to add a non functioning set up so i can drag frame everywhere. although my prefered ride height would be equal to that of diez's car. neither 4x4 or dumped but a good functional height.
i almost want to keep the konis and swap the front springs to the rear to go softer in the rear but seeing as my car is my DD i cant have down time soi wouldnt be able to send off my only struts to be re valved so it would need to be a direct swap.
either way, any and all feedback is welcomed. thanks
08-31-2010, 02:06 PM
#3
Registered User
Join Date: Jul 2007
Posts: 1,376
Likes: 0
Received 0 Likes
on
0 Posts
OK, I'm going to add my 2 cents to this thread...take it with a grain of salt. I've been researching the S2k chassis and suspension system for a while, trying to decide what route to take with modifications. Here's what I have learned... Feel free to correct me, if you think I've mistakenly said something.
References I've been using:
Milliken's Race Car Vehicle Dynamics
Dennis Grant (Far North Racing) also has a lot of very applicable information & suggestions regarding suspension tuning on his website. Take some time to read through all of it...maybe read it twice or three times. You'll have a new outlook on suspension and why it pays to use well-designed (read: well engineered, manufactured and tested) hardware. The information focuses on auto-x suspension setups but can be applied to daily driving or tracking. Enough of a free plug, I think...
Cliff notes to the above references: You should care about low speed damping characteristics (0-3 in/sec). Damping coefficients of 0.7 front and rear are good starting points for low-speed damper velocities. Above those speeds, shoot for 0.25 damping coefficients. Natural frequencies of 2.2Hz front and 2.5Hz rear will get you in the ball-park, as far as spring rates are concerned.
Application of the above to the S2k chassis:
Once you've digested all of that, you can start comparing the suggestions to the stock S2k chassis and research how best to improve upon the stock system. For reference, my script calculates the MY00 natural frequencies to be 1.31Hz front and 1.54Hz rear. In order to increase the natural frequencies to the suggested levels, you'll need spring rates of about 600 lb/in front and 750 lb/in rear. It is not uncommon to swap the natural frequencies, i.e. 2.5Hz front and 2.2Hz rear. It's also a good idea to maintain a difference between the front and rear natural frequencies. This will help decrease chassis pitch and give you a more pleasant ride.
The route I've chosen:
Bilstein PSS (& PSS9) kits are a decent starting point, if you are OK with modifying them. "As is" from Bilstein, they are not rebuildable. A schrader valve will need to be added into order to refill the nitrogen charge after reassembling them. There are more than a handful of shops that have experience building Bilstein dampers. Bilsteins in general are often used in oval-race applications. Bilstein does not make a cheap adjustable shaft. Their adjustable shaft is about $400 per corner, last time I had it priced out. Once you get the damping right, you shouldn't need to adjust it, though. The PSS9 adjuster has poor resolution (~180 degree total sweep), making repeatability very difficult. The stock PSS spring rates are too low for racing applications and the damper will need to be revalved in order to support higher spring rates.
The OE top hats are not ideal and I've come up with a conceptual top hat to replace them.
The above design will transmit all of the load through the spherical bearing and keep the spring coaxial with the damper at all times, which the OE design does not achieve. The thrust bearing is there to eliminate spring binding as the assembly is compressed and released. Hope that gives you guys some ideas of how to build a legit top hat.
In order to use standard 2.25" or 2.5" ID springs, the lower Bilstein spring perch will need to be cut down. The standard Bilstein springs are a larger ID...something like 2.75"?
Common misconceptions/misstatements:
- Dampening = making something wet
- Damping = shocks
- 32 way adjustable shocks do not exist. "N" adjustments refers to the damping adjustments. Rebound only = 1 way adjustable. Rebound and compression together = 1 way adjustable. Rebound and compression separate = 2 way adjustable. High and low speed can be added to the previous levels of adjusting, which will account for up to 4-way adjustable dampers. Height adjustment does not count!
_________________________________________
None of the above is intended to insult anyone or rag on any aftermarket parts. It's merely what I have learned over the past year or so of research.
Cheers
References I've been using:
Milliken's Race Car Vehicle Dynamics
Dennis Grant (Far North Racing) also has a lot of very applicable information & suggestions regarding suspension tuning on his website. Take some time to read through all of it...maybe read it twice or three times. You'll have a new outlook on suspension and why it pays to use well-designed (read: well engineered, manufactured and tested) hardware. The information focuses on auto-x suspension setups but can be applied to daily driving or tracking. Enough of a free plug, I think...
Cliff notes to the above references: You should care about low speed damping characteristics (0-3 in/sec). Damping coefficients of 0.7 front and rear are good starting points for low-speed damper velocities. Above those speeds, shoot for 0.25 damping coefficients. Natural frequencies of 2.2Hz front and 2.5Hz rear will get you in the ball-park, as far as spring rates are concerned.
Application of the above to the S2k chassis:
Once you've digested all of that, you can start comparing the suggestions to the stock S2k chassis and research how best to improve upon the stock system. For reference, my script calculates the MY00 natural frequencies to be 1.31Hz front and 1.54Hz rear. In order to increase the natural frequencies to the suggested levels, you'll need spring rates of about 600 lb/in front and 750 lb/in rear. It is not uncommon to swap the natural frequencies, i.e. 2.5Hz front and 2.2Hz rear. It's also a good idea to maintain a difference between the front and rear natural frequencies. This will help decrease chassis pitch and give you a more pleasant ride.
The route I've chosen:
Bilstein PSS (& PSS9) kits are a decent starting point, if you are OK with modifying them. "As is" from Bilstein, they are not rebuildable. A schrader valve will need to be added into order to refill the nitrogen charge after reassembling them. There are more than a handful of shops that have experience building Bilstein dampers. Bilsteins in general are often used in oval-race applications. Bilstein does not make a cheap adjustable shaft. Their adjustable shaft is about $400 per corner, last time I had it priced out. Once you get the damping right, you shouldn't need to adjust it, though. The PSS9 adjuster has poor resolution (~180 degree total sweep), making repeatability very difficult. The stock PSS spring rates are too low for racing applications and the damper will need to be revalved in order to support higher spring rates.
The OE top hats are not ideal and I've come up with a conceptual top hat to replace them.
The above design will transmit all of the load through the spherical bearing and keep the spring coaxial with the damper at all times, which the OE design does not achieve. The thrust bearing is there to eliminate spring binding as the assembly is compressed and released. Hope that gives you guys some ideas of how to build a legit top hat.
In order to use standard 2.25" or 2.5" ID springs, the lower Bilstein spring perch will need to be cut down. The standard Bilstein springs are a larger ID...something like 2.75"?
Common misconceptions/misstatements:
- Dampening = making something wet
- Damping = shocks
- 32 way adjustable shocks do not exist. "N" adjustments refers to the damping adjustments. Rebound only = 1 way adjustable. Rebound and compression together = 1 way adjustable. Rebound and compression separate = 2 way adjustable. High and low speed can be added to the previous levels of adjusting, which will account for up to 4-way adjustable dampers. Height adjustment does not count!
_________________________________________
None of the above is intended to insult anyone or rag on any aftermarket parts. It's merely what I have learned over the past year or so of research.
Cheers
08-31-2010, 02:33 PM
#4
Registered User
Join Date: Jul 2007
Posts: 1,376
Likes: 0
Received 0 Likes
on
0 Posts
I should also add that the stock suspension is very well designed, in my opinion, and will be difficult to improve upon. At the last lapping day I attended, my data logs show sustained 1.15 Gs during turns...on street tires...with data smoothing. That's almost as high as the sustained 1.2+ Gs I use to see using auto-x r-comps. My only suspension modification is a stiffened Saner FSB (added 4th adjustment hole). 17x9 wheels and non staggered 255 tires helped tremendously.
08-31-2010, 03:58 PM
#5
Originally Posted by nmrado,Aug 31 2010, 02:06 PM
OK, I'm going to add my 2 cents to this thread...take it with a grain of salt. I've been researching the S2k chassis and suspension system for a while, trying to decide what route to take with modifications. Here's what I have learned... Feel free to correct me, if you think I've mistakenly said something.
References I've been using:
Milliken's Race Car Vehicle Dynamics
Dennis Grant (Far North Racing) also has a lot of very applicable information & suggestions regarding suspension tuning on his website. Take some time to read through all of it...maybe read it twice or three times. You'll have a new outlook on suspension and why it pays to use well-designed (read: well engineered, manufactured and tested) hardware. The information focuses on auto-x suspension setups but can be applied to daily driving or tracking. Enough of a free plug, I think...
Cliff notes to the above references: You should care about low speed damping characteristics (0-3 in/sec). Damping coefficients of 0.7 front and rear are good starting points for low-speed damper velocities. Above those speeds, shoot for 0.25 damping coefficients. Natural frequencies of 2.2Hz front and 2.5Hz rear will get you in the ball-park, as far as spring rates are concerned.
Application of the above to the S2k chassis:
Once you've digested all of that, you can start comparing the suggestions to the stock S2k chassis and research how best to improve upon the stock system. For reference, my script calculates the MY00 natural frequencies to be 1.31Hz front and 1.54Hz rear. In order to increase the natural frequencies to the suggested levels, you'll need spring rates of about 600 lb/in front and 750 lb/in rear. It is not uncommon to swap the natural frequencies, i.e. 2.5Hz front and 2.2Hz rear. It's also a good idea to maintain a difference between the front and rear natural frequencies. This will help decrease chassis pitch and give you a more pleasant ride.
The route I've chosen:
Bilstein PSS (& PSS9) kits are a decent starting point, if you are OK with modifying them. "As is" from Bilstein, they are not rebuildable. A schrader valve will need to be added into order to refill the nitrogen charge after reassembling them. There are more than a handful of shops that have experience building Bilstein dampers. Bilsteins in general are often used in oval-race applications. Bilstein does not make a cheap adjustable shaft. Their adjustable shaft is about $400 per corner, last time I had it priced out. Once you get the damping right, you shouldn't need to adjust it, though. The PSS9 adjuster has poor resolution (~180 degree total sweep), making repeatability very difficult. The stock PSS spring rates are too low for racing applications and the damper will need to be revalved in order to support higher spring rates.
The OE top hats are not ideal and I've come up with a conceptual top hat to replace them.
The above design will transmit all of the load through the spherical bearing and keep the spring coaxial with the damper at all times, which the OE design does not achieve. The thrust bearing is there to eliminate spring binding as the assembly is compressed and released. Hope that gives you guys some ideas of how to build a legit top hat.
In order to use standard 2.25" or 2.5" ID springs, the lower Bilstein spring perch will need to be cut down. The standard Bilstein springs are a larger ID...something like 2.75"?
Common misconceptions/misstatements:
- Dampening = making something wet
- Damping = shocks
- 32 way adjustable shocks do not exist. "N" adjustments refers to the damping adjustments. Rebound only = 1 way adjustable. Rebound and compression together = 1 way adjustable. Rebound and compression separate = 2 way adjustable. High and low speed can be added to the previous levels of adjusting, which will account for up to 4-way adjustable dampers. Height adjustment does not count!
_________________________________________
None of the above is intended to insult anyone or rag on any aftermarket parts. It's merely what I have learned over the past year or so of research.
Cheers
References I've been using:
Milliken's Race Car Vehicle Dynamics
Dennis Grant (Far North Racing) also has a lot of very applicable information & suggestions regarding suspension tuning on his website. Take some time to read through all of it...maybe read it twice or three times. You'll have a new outlook on suspension and why it pays to use well-designed (read: well engineered, manufactured and tested) hardware. The information focuses on auto-x suspension setups but can be applied to daily driving or tracking. Enough of a free plug, I think...
Cliff notes to the above references: You should care about low speed damping characteristics (0-3 in/sec). Damping coefficients of 0.7 front and rear are good starting points for low-speed damper velocities. Above those speeds, shoot for 0.25 damping coefficients. Natural frequencies of 2.2Hz front and 2.5Hz rear will get you in the ball-park, as far as spring rates are concerned.
Application of the above to the S2k chassis:
Once you've digested all of that, you can start comparing the suggestions to the stock S2k chassis and research how best to improve upon the stock system. For reference, my script calculates the MY00 natural frequencies to be 1.31Hz front and 1.54Hz rear. In order to increase the natural frequencies to the suggested levels, you'll need spring rates of about 600 lb/in front and 750 lb/in rear. It is not uncommon to swap the natural frequencies, i.e. 2.5Hz front and 2.2Hz rear. It's also a good idea to maintain a difference between the front and rear natural frequencies. This will help decrease chassis pitch and give you a more pleasant ride.
The route I've chosen:
Bilstein PSS (& PSS9) kits are a decent starting point, if you are OK with modifying them. "As is" from Bilstein, they are not rebuildable. A schrader valve will need to be added into order to refill the nitrogen charge after reassembling them. There are more than a handful of shops that have experience building Bilstein dampers. Bilsteins in general are often used in oval-race applications. Bilstein does not make a cheap adjustable shaft. Their adjustable shaft is about $400 per corner, last time I had it priced out. Once you get the damping right, you shouldn't need to adjust it, though. The PSS9 adjuster has poor resolution (~180 degree total sweep), making repeatability very difficult. The stock PSS spring rates are too low for racing applications and the damper will need to be revalved in order to support higher spring rates.
The OE top hats are not ideal and I've come up with a conceptual top hat to replace them.
The above design will transmit all of the load through the spherical bearing and keep the spring coaxial with the damper at all times, which the OE design does not achieve. The thrust bearing is there to eliminate spring binding as the assembly is compressed and released. Hope that gives you guys some ideas of how to build a legit top hat.
In order to use standard 2.25" or 2.5" ID springs, the lower Bilstein spring perch will need to be cut down. The standard Bilstein springs are a larger ID...something like 2.75"?
Common misconceptions/misstatements:
- Dampening = making something wet
- Damping = shocks
- 32 way adjustable shocks do not exist. "N" adjustments refers to the damping adjustments. Rebound only = 1 way adjustable. Rebound and compression together = 1 way adjustable. Rebound and compression separate = 2 way adjustable. High and low speed can be added to the previous levels of adjusting, which will account for up to 4-way adjustable dampers. Height adjustment does not count!
_________________________________________
None of the above is intended to insult anyone or rag on any aftermarket parts. It's merely what I have learned over the past year or so of research.
Cheers
08-31-2010, 05:31 PM
#6
Registered User
Join Date: Jul 2007
Posts: 1,376
Likes: 0
Received 0 Likes
on
0 Posts
Originally Posted by Carbon Blue,Aug 31 2010, 05:58 PM
with all that said, what suspension setup do you run nmrado?
09-02-2010, 04:20 AM
#7
Registered User
Thread Starter
well, thanks for the input. as far as customizing goes, i think i may end up ordering custom springs from swift or eibach and putting them on the bilstein dampers.
Trending Topics
09-02-2010, 09:40 AM
#9
Originally Posted by nmrado,Aug 31 2010, 02:06 PM
Application of the above to the S2k chassis:
Once you've digested all of that, you can start comparing the suggestions to the stock S2k chassis and research how best to improve upon the stock system. For reference, my script calculates the MY00 natural frequencies to be 1.31Hz front and 1.54Hz rear. In order to increase the natural frequencies to the suggested levels, you'll need spring rates of about 600 lb/in front and 750 lb/in rear. It is not uncommon to swap the natural frequencies, i.e. 2.5Hz front and 2.2Hz rear. It's also a good idea to maintain a difference between the front and rear natural frequencies. This will help decrease chassis pitch and give you a more pleasant ride.
Once you've digested all of that, you can start comparing the suggestions to the stock S2k chassis and research how best to improve upon the stock system. For reference, my script calculates the MY00 natural frequencies to be 1.31Hz front and 1.54Hz rear. In order to increase the natural frequencies to the suggested levels, you'll need spring rates of about 600 lb/in front and 750 lb/in rear. It is not uncommon to swap the natural frequencies, i.e. 2.5Hz front and 2.2Hz rear. It's also a good idea to maintain a difference between the front and rear natural frequencies. This will help decrease chassis pitch and give you a more pleasant ride.
09-03-2010, 03:51 AM
#10
Registered User
Join Date: Jan 2010
Posts: 23
Likes: 0
Received 0 Likes
on
0 Posts
Just an FYI Tein makes top mounts that have a bearing and work with 70mm(2.75") I.D. springs. 70mm I.D. are not hard to find they just have less selection (10k, 12k, 14k).
Also, having a separate upper spring perch is the ideal setup, but I have not been able to find any off the shelf version, yet.
The Tein's tops will need new springs, because the stock Bilsteins springs are tapered to fit into the stock top mounts.
Also, having a separate upper spring perch is the ideal setup, but I have not been able to find any off the shelf version, yet.
The Tein's tops will need new springs, because the stock Bilsteins springs are tapered to fit into the stock top mounts.