: CTS-V Suspension Tuning



FuzzyLogic
06-23-13, 05:44 AM
All,

I thought I'd start a thread dedicated to CTS-V suspension tuning because:

I've read almost every CTS-V suspension-tuning thread on LS1Tech and the Cadillac Forums and felt that there was a lack of clear guidance.
I've invested about $3500 into my suspension and I hope that, through reading this thread, others will save time and money.
I appreciate your input and I hope that you guys will provide a sanity check on my calculations and assumptions.

But before we can have an intelligent conversation, we have to know (roughly) the corner weight and suspension geometry of the CTS-V. I've done most of the legwork on this already:

CTS-V1 Curb Weight:
3850 lbs with a 54/46 weight distribution
Assumed to be 4000 lbs after about $5,000 of common modifications and a 200 lb driver.

CTS-V1 Corner Weight:
1080 lbs front (4000*0.54/2) and 920 lbs (4000*0.46/2) rear.

CTS-V1 Unsprung Corner Weight:
150 lbs front and 140 lbs rear.**

CTS-V1 Sprung Weight:
930 lbs front and 780 lbs rear

Front Shock Measurements:
d1 = 10"
d2 = 17"
theta = 20 degree from vertical

Rear Spring Measurements (for Ground Control / KW Variant 3 users):
d1 = 11"
d2 = 22"
theta = 10 degrees from vertical

Rear Shock Measurements (for k-Sport / LG Coilover users):
d1 = 11"
d2 = 14"
theta = 15 degrees from vertical

http://yw1015.tripod.com/images/diagram1.gif

The first thing to note is that using the spring perch results in a motion ratio of 2:1, whereas using the shock perch results in a 1.27:1 ratio. This produces an effective spring rate 1.575 times higher. In other words, moving a 500-in lb spring from the spring perch to the shock perch effectively transforms it into a 787 lb spring.


**Justification:
Unsprung weight, by and large, consists of wheels, tires, axles, hubs, brake calipers, control arms, shocks, springs, and sway bars. I understand that some of these items contribute a percentage of their mass between sprung and unsprung categories. This is an acknowledged source of error. Also, I have not weighed the control arms, hubs, brake calipers, or axles. Through the process of elimination, however, I feel confident that the following estimate is good enough for our purposes.


The stock 18x8.5" Speedline wheels (28.5 lbs each) with stock 245/45-18" Goodyear F1 Supercar EMT tires (31 lbs each) = 59.5 lbs per corner.

The stock front rotors weigh 25.5 lbs apiece. The rear rotors are about a pound and a half lighter, but internally, our cars have a parking brake shoe that makes up the difference. Quality GS3500 aftermarket rotors (e.g. DRT rotors) are about a pound heavier on each corner. 87 lbs so far per corner.

The stock FG2 shock body (minus spring) weighs 8.6 lbs (front) and 7.4 lbs (rear), respectively. Each 2.50" ID, 10"-long Eibach spring weighs 6.2 lbs, bringing the assembled weight of each Ground Control/FG2 corner up to 14.8 lbs and 13.6 lbs respectively. 102 lbs front and 100 lbs rear per corner.

The Hotchkis 2280 front and rear sway bars weigh 9.0 lbs and 7.4 lbs (4.5 lbs and 3.7 lbs per corner). This is probably within two pounds of the stock sway bars. 107 lbs front and 104 lbs rear per corner.

Finally, we have to guess about the control arms. Since the front has significantly beefier control arms, including that cast vertical section, I'm going to assign 50% more weight to the front control arms, or 24 lbs to the front control arms and 16 lbs to the rear control arms. 131 lbs front and 120 lbs rear.

The front brake calipers weigh about a pound more than the rear calipers, but this is balanced out by the rear axles, which weigh at least five pounds more than the front axles. Once you factor in the trailing arms (which weigh about five pounds) and hubs, I'm going to assign 19 lbs to the front and 20 lbs to the rear to complete the assembly, bringing us up to 150 lbs front and 140 lbs rear.

----------

Let's run through a couple of typical off-the-shelf configurations, using the Racing Aspirations calculator (http://www.racingaspirations.com/wheel-frequency-calculator), plus a couple of interesting modifications by Junior1 and myself:

500/550 Ground Control
Front/Rear Effective Coil Rate: 295.85 and 275 lbs/in
Front/Rear Wheel Rate: 175.06 and 137.5 lbs/in
Front/Rear Wheel Frequency: 81.49 and 78.86 cpm
Front/Rear Natural Frequency: 1.35 and 1.31 Hz

Front/Rear Bias: +3%

574/514 KW Variant 3
Front/Rear Effective Coil Rate: 339.64 and 257 lbs/in
Front/Rear Wheel Rate: 200.97 and 128.5 lbs/in
Front/Rear Wheel Frequency: 87.37 and 76.22 cpm
Front/Rear Natural Frequency: 1.45 and 1.27 Hz

Front/Rear Bias: +14%

700/400 LG Motorsports
Front/Rear Effective Coil Rate: 414.2 and 314.96 lbs/in
Front/Rear Wheel Rate: 245.08 and 248 lbs/in
Front/Rear Wheel Frequency: 96.46 and 105.98 cpm
Front/Rear Natural Frequency: 1.6 and 1.76 Hz

Front/Rear Bias: -10%

900/500 "Junior1" Penske Triple Adjustable config
Front/Rear Effective Coil Rate: 532.54 and 393.7 lbs/in
Front/Rear Wheel Rate: 315.11 and 310 lbs/in
Front/Rear Wheel Frequency: 109.34 and 118.53 cpm
Front/Rear Natural Frequency: 1.82 and 1.97 Hz

Front/Rear Bias: -8%

672/896 "FuzzyLogic" KW Variant 3 config
Front/Rear Effective Coil Rate: 397.63 and 448 lbs/in
Front/Rear Wheel Rate: 235.28 and 224 lbs/in
Front/Rear Wheel Frequency: 94.49 and 100.67 cpm
Front/Rear Natural Frequency: 1.57 and 1.67 Hz

Front/Rear Bias: -6%

The first thing that you need to note about the above numbers is the fact that the standard Ground Control and KW Variant 3 configurations royally effed up their frequency ratios. Generally speaking, you want your rear wheel frequency to be 10-20% higher than the front to prevent pitch and promote a flat ride, which is comfortable. Read more about it (and some of the exceptions to this rule) here courtesy of OptimumG (http://www.optimumg.com/docs/Springs&Dampers_Tech_Tip_1.pdf). I can only surmise that both vendors either didn't take measurements, or took measurements from the rear shock perches instead of the spring perches, which is where the car is going to put leverage on the springs.

The other thing you should note is that Junior1's car actually weighs 3566 lbs (with driver), due to the fact that he's stripped out the interior, glass, seats, and purchased the prototype carbon fiber doors and trunk that Spectre Werkes built before they went out of business. As a result, his corner weights are about 100 lbs less than ours, and a little bit better biased toward perfect 50/50 distribution (roughly 53/47). As a result, his actual natural frequencies are going to be more what you'd expect from a full-blown racecar: 1.99 Hz front and 2.11 Hz rear.

Since I'm not beholden to the rules and regulations governing Junior1's track events, I can put a heavy engine, supercharger, and intercooler in my car that will further exacerbate the existing weight distribution problem. My spring rates already take this into account: once you add 200 lbs of weight to the front end of the car (100 lbs per corner), the natural frequency of my front suspension drops to 1.49 Hz, which is almost dead-nuts on my 1.50 Hz target for a "sedan racecar" and results in a good -12% bias to prevent pitch and increase ride comfort.

----------

At this point, I'd like to invite any and all comments and questions you may have.

In general, I was not surprised by the results of this exercise. Ever since I upgraded to the KW Variant 3, I noticed how much I had to use the variable low-speed valving settings on the shocks to effectively "band-aid" the effect of the soft rear springs included with the kit. Having experimented with about $800 worth of Eibach springs and the Ground Control kit, I knew from previous experience that I needed at least 100 (and preferrably 150) lbs/in worth of additional rate in the rear to make the car respond crisply to inputs.

I'd also like to note that one look at the wheel rates blows any worries about damaging the KW Variant 3 with a high rear spring rate out of the water. According to AAIIIC, KW once stated that "our shocks can only handle about 200 in-lbs more spring than the kit includes." Looking at the effective wheel coil rate of the front suspension (339.64 lbs/in with the 574 lbs/in spring), 200 additional lbs/in (i.e.: a 774 lbs/in spring) would present an effective coil rate of 457.98 lbs/in to the shock. By the same rationale, the 896 in-lb spring with the rear geometry presents an effective coil rate of 448 lbs/in to the rear shocks, which is less than 457.98 lbs/in.

odla
06-24-13, 10:27 PM
Thanks for the work and time you put into this.

hambycm
06-25-13, 09:18 AM
At this point, I'd like to invite any and all comments and questions you may have.



How do sway bars impact the equation, and how do you begin to tune them to integrate well with the rest of the setup (or perhaps tune the rest of the setup to work with them)?

verywhitedevil
06-25-13, 10:51 AM
excellent work fuzzy. my setup is FG2/Ground Control 500/550 / PFADT upper rear shock corvette mounts. I am sure other parts do come in to play here such as Spectre Werks cradle bushings (your case REVSHIFT), Sway bars, etc...?? Q: would you suggest to start in the rear and bump up the spring rate say 150 lbs to try and get the frequency in check?

FuzzyLogic
06-25-13, 12:09 PM
How do sway bars impact the equation, and how do you begin to tune them to integrate well with the rest of the setup (or perhaps tune the rest of the setup to work with them)?

You can ask a hundred different people that question and get a hundred different answers. I don't want to get launched into a debate on the subject of sway bars. The purpose of a swaybar is to distribute load across the suspension of a cornering car. That we all agree on. The rest is a mishmash of suspension tuning methodologies peppered with both good and bad ideas.

What I will say is this: get your natural frequencies in line before selecting a sway bar. Don't buy more bar than you need. If your roads are terrible, a big sway bar is going to have a deleterious effect on ride quality because it reduces the independence of your left and right wheels. The smoother your roads, the higher your spring rates and natural frequencies can be, which will increase corner stiffness and reduce your reliance on sway bars. Factor in the cost of an alignment (or several). Sway bars will affect your handling balance because they change the amount of load each wheel sees in a turn. This, in turn, affects the slip angle and camber angle of each wheel, but those characteristics can be tweaked (and even reversed) with a well-engineered alignment.

----------


excellent work fuzzy. my setup is FG2/Ground Control 500/550 / PFADT upper rear shock corvette mounts. I am sure other parts do come in to play here such as Spectre Werks cradle bushings (your case REVSHIFT), Sway bars, etc...?? Q: would you suggest to start in the rear and bump up the spring rate say 150 lbs to try and get the frequency in check?

The problem with the Ground Control kit is that the rear perches are limited in their adjustability, since don't have a lot of thread on them. Most of the spring rates you'll want require a 9" long spring to fit correctly, which Eibach and Hypercoil don't sell. That only leaves you with Swift (http://www.swiftsprings.net/products/universal/metric-coilover-springs.html), which is the best (albeit most expensive) spring manufacturer--and they only sell metric springs.

If you want to keep your current front springs, I recommend trying a pair of of Z65-228-120 (65mm, 9" length, 120 N-m or 672 lbs/inch) springs in the rear. That'll bring you up to 1.45 Hz in the rear, or a -7% bias (a little low given our wheelbase, but probably good enough). Alternately, you could switch your 550 lbs/in rear springs to the front and buy a set of Z65-228-140 (140 N-m or 784 lbs/inch) springs for the rear. That would increase your front natural frequency to 1.42 Hz and rear to 1.57 Hz (-10% bias).

Of course, in both cases, your rear end will be massively underdamped since the rear FG2s' fixed rebound valving was set for a 363-395 lbs/inch progressive spring. I've never gone above 700 lbs/in on the rear with FG2s, but I suspect that with the fixed FG2 compression settings, the rear end might be harsh enough to launch groceries in the trunk. Why don't you try it and let us know? :halo:

sssnake
06-25-13, 03:54 PM
Very good post. I would/will have to study much more on suspension before I could add anything meaningful. Thanks!

verywhitedevil
06-25-13, 05:54 PM
"The problem with the Ground Control kit is that the rear perches are limited in their adjustability, since don't have a lot of thread on them. Most of the spring rates you'll want require a 9" long spring to fit correctly"

- regarding the rear perches, the bottoms are fixed so I am assuming you are talking about the top mounts. so you think the 9" spring will work in place of the 10" without modification or should maybe I look into making that threaded piece longer (still utilizing the colllar)??? any machine shop should be able to make me that threaded piece if I take them the GC one. you think this would help at all with the 9"? I will definitely look into swapping the rear springs to front and buy a set of Z65-228-140 (140 N-m or 784 lbs/inch). 9" spring 784/bs is this relative to a 700 lb 10" spring?? I have the collar maxed to the top anyways, so why would more thread even matter???

technically once the FG2's are done, I will select a different shock at that time. Maybe there is a good replacement for rear only shocks. I know Sachs put the FG2's out there without the fixed rebound valving but they are rare. called T2 or something. that would be ideal at least for a FG/GC setup.

thanks for your imput. I really appreciate it. trying to understand why going to the 9" spring helps.

FuzzyLogic
06-25-13, 11:28 PM
I should've been clearer earlier. Stiffer springs don't compress as much under normal loading. Once you exceed 600 or 650 in-lbs with 10" long rear springs, you won't be able to get the back end of your car to sit low enough.

The next size down that Eibach sells is an 8" spring. A 700 in-lb, 8" spring will almost work, but (based on personal experience) you'll have to leave that gold GC ring hanging off the last couple of threads of the red threaded piece. That's dangerous. On top of that, when you take the car off the ground, a gap will open up between the top of the spring and the gold ring, and the springs may fall out. To solve the problem, you could have a shop build you a longer threaded piece, but by the time you go through all of that trouble, you might as well have bought a pair of 9" Swift springs.

verywhitedevil
06-26-13, 01:34 AM
word. 9" swift springs here i come. did you end up selling your set?

UnsafeAtAnySpd
06-26-13, 01:37 AM
Great thread idea. I hate that I haven't been able to get track times since my suspension upgrades. Now that I'm moving, once I do make it to the track I won't have good before/after info.

The one math class I've taken over the course of my undergrad and graduate work doesn't help me much here. :D

I have some corner weight info from my car if it helps at all here (if not, I can remove this post as I don't want to clutter the thread too much).


I don't think that I posted this info in this thread, but I corner weighed my car at the track early last season.



Quote:


Originally Posted by UnsafeAtAnySpd View Post

I figured some of you would like to know these numbers. These were taken with me in the car (about 168 lbs), my helmet in the passenger seat, about a half tank of gas, a few trunk interior pieces removed, some dynamat back there, Kooks headers, hi-flow cats, Corsa catback, sunroof, rear strut tower brace, BMR front brace, Optima redtop in stock location.

LF 1114 1084 RF
LR 924 896 RR

Front 2198
Rear 1820
Total 4018

I went ahead and weighed it again yesterday. Changes are the clutch/flywheel, wheels/tires, rear seat removed, maybe a quarter tank of gas less (if that) and I've gained about 20 lbs...

3886 lbs!

No current corner weights after roll bar/seat install.

So it appears there is a slight passenger side weight bias (since I was in the car for these weights). Also, at my current ride height (about 14" from fender lip to center of hub all around), I was getting a slight rub only on the passenger side on dips in the highway (285 tires on TD wheels) with a bit of luggage in the trunk and my 100 lbs girlfriend in the passenger seat.

FuzzyLogic
06-26-13, 08:25 AM
Thanks for the input, UnsafeatanySpd. Measured data is always appreciated. It's interesting to know that your weight counterbalanced the inherently heavier passenger side, yet the curse of the passenger side rubbing remained.

thebigjimsho
06-26-13, 12:57 PM
Great thread, Fuzzy. Good to see numbers and in-depth analysis on everything suspension. The amount of focus on just dyno numbers with such a great handling car annoys me.

BradCTSV
06-29-13, 03:53 AM
Thanks, great analysis! My V is in the shop as we speak....I will post in next couple of weeks as to what I end up doing on my suspension.

AAIIIC
06-29-13, 03:53 PM
I've always been too lazy to look into all this stuff - I just buy off the shelf bits and figure someone else has done the homework. :lol: With that said, I did think it was a bit strange (from a handling balance perspective) that the KW V3s had stiffer springs in the front than in the rear, unlike the stock V setup, which is matched. So, I swapped out the rears for new springs that matched the front rate pretty quickly. I can't say I noticed any difference in ride comfort / pitch with either setup - both felt/feel fine to me. What I've been told in the past, when I was trying to resolve a suspension bounciness with my Subaru, is to rest one's head back against the headrest as you're driving to determine if there's any front/rear mismatch. If a bump causes your head to bounce forward off the headrest, then the two ends of the car aren't reacting in concert. Not the most scientific thing, I'm sure, but my car passes that test.


The first thing that you need to note about the above numbers is the fact that the standard Ground Control and KW Variant 3 configurations royally effed up their frequency ratios. Generally speaking, you want your rear wheel frequency to be 10-20% higher than the front to prevent pitch and promote a flat ride, which is comfortable.
Well, apparently those stupid GM engineers royally effed up their frequency ratios, too, because the V's stock spring rates (400f/400r) would give a higher frequency up front. The V6 CTS's spring rates (which I believe are 340f/300r, or something like that) would have an even larger front bias, and thus an even more uncomfortable ride.


I can only surmise that both vendors either didn't take measurements, or took measurements from the rear shock perches instead of the spring perches, which is where the car is going to put leverage on the springs.
I can only surmise that there's more to this than what is encompassed in a 3 page PDF on the internet. ;) I don't know of anyone that finds a pitching problem with either stock suspension setup, despite what the numbers would say.


I'd also like to note that one look at the wheel rates blows any worries about damaging the KW Variant 3 with a high rear spring rate out of the water. According to AAIIIC, KW once stated that "our shocks can only handle about 200 in-lbs more spring than the kit includes." Looking at the effective wheel coil rate of the front suspension (339.64 lbs/in with the 574 lbs/in spring), 200 additional lbs/in (i.e.: a 774 lbs/in spring) would present an effective coil rate of 457.98 lbs/in to the shock. By the same rationale, the 896 in-lb spring with the rear geometry presents an effective coil rate of 448 lbs/in to the rear shocks, which is less than 457.98 lbs/in.
That assumes they use the same damper at both ends of the car; I don't know if that's the case. They pretty much look the same externally (other than the obvious differences in mounting), but I don't know about the guts.

FuzzyLogic
06-29-13, 05:58 PM
I've always been too lazy to look into all this stuff - I just buy off the shelf bits and figure someone else has done the homework. :lol: With that said, I did think it was a bit strange (from a handling balance perspective) that the KW V3s had stiffer springs in the front than in the rear, unlike the stock V setup, which is matched. So, I swapped out the rears for new springs that matched the front rate pretty quickly. I can't say I noticed any difference in ride comfort / pitch with either setup - both felt/feel fine to me. What I've been told in the past, when I was trying to resolve a suspension bounciness with my Subaru, is to rest one's head back against the headrest as you're driving to determine if there's any front/rear mismatch. If a bump causes your head to bounce forward off the headrest, then the two ends of the car aren't reacting in concert. Not the most scientific thing, I'm sure, but my car passes that test.

For what it's worth, that test is effing retarded. Your head will bounce forward at certain speeds with every possible spring/shock tuning for a given wheelbase.

By the way, if you installed 574 in-lb rear springs, your rear frequency only changed from 1.27 to 1.34 Hz, which isn't nearly enough. If you wanted equal front and rear rates (which is still way wrong), you should've bought 672 in-lb springs. Ideally, you should be running Swift's 1008 in-lb springs in the rear with the 672 in-lb front springs that I suggested, but I know from experience that the percentage split with 896 in-lb springs will be a massive improvement.

I encourage you to try a pair of Swift Z60-228-140 (9" length, 784 in-lbs) springs--there's an amazing difference in the way the car corners with the proper support because you're no longer transferring an excessive amount of weight away from the front wheels under cornering load.


Well, apparently those stupid GM engineers royally effed up their frequency ratios, too, because the V's stock spring rates (400f/400r) would give a higher frequency up front. The V6 CTS's spring rates (which I believe are 340f/300r, or something like that) would have an even larger front bias, and thus an even more uncomfortable ride.

Those GM engineers also included rubber motor mounts that crack, dry out, and fail in less than 20,000 miles and a Pontiac Solstice differential on a car that can put more than 375 ft-lbs of torque. The car comes stock with a 50+ lb flywheel to improve driveability for senior citizens and an electronic feature that locks out second and third gear in intersections.


I can only surmise that there's more to this than what is encompassed in a 3 page PDF on the internet. ;) I don't know of anyone that finds a pitching problem with either stock suspension setup, despite what the numbers would say.

I posted the shortest and easiest to understand PDF I had, because I've found from prior experience that most people won't read 20-50 page technical dissertations without pictures. I can say for certain that the stock tuning has a pitching problem (see my initial response above)--my daily drive features two unavoidable bumps that produce terrific pitch with the stock suspension, the stock Ground Control setup, and the stock KW Variant 3 setup. It can be tuned out with proper spring selection. The car feels amazing once you get the balance right.


That assumes they use the same damper at both ends of the car; I don't know if that's the case. They pretty much look the same externally (other than the obvious differences in mounting), but I don't know about the guts.

Valid point. I considered that earlier. Regardless, I seriously doubt that you'll damage a shock absorber with too much spring, unless there's some way to warp the rebound valving by forcing too much fluid through the opening, too fast.

FuzzyLogic
07-20-13, 01:24 AM
Guess what time it is?

http://i1345.photobucket.com/albums/p663/Fuzzylog1c/DSC00845_zpsd79430f4.jpg (http://s1345.photobucket.com/user/Fuzzylog1c/media/DSC00845_zpsd79430f4.jpg.html)
Swift Z70-203-120 springs (672 in-lbs) and Swift Z60-228-160 springs (896 in-lbs)

http://i1345.photobucket.com/albums/p663/Fuzzylog1c/DSC00826_zps2c0595ee.jpg (http://s1345.photobucket.com/user/Fuzzylog1c/media/DSC00826_zps2c0595ee.jpg.html)
Banski Motorsports Prototype Spherical CTS-V RSMs

BradCTSV
07-20-13, 03:28 AM
Since I'm lucky enough to live near Sonoma Raceway, CA, I had Performance Shock dyno my LG Motorsport/Bilstein coilovers. The rebound was significantly increased on both front and rear shocks--the difference on the road is HUGE!! On top of that I ordered CCW SP600's (19x8.5 and 9.5) in satin black with Hankook RS3's (245/40 and 275/35).

RyRidesMotoX
07-20-13, 04:43 AM
Since I'm lucky enough to live near Sonoma Raceway, CA, I had Performance Shock dyno my LG Motorsport/Bilstein coilovers. The rebound was significantly increased on both front and rear shocks--the difference on the road is HUGE!! On top of that I ordered CCW SP600's (19x8.5 and 9.5) in satin black with Hankook RS3's (245/40 and 275/35).

I thought I was the only one that liked Hankook rs3 tires on my cars. It seems like everyone uses Michelin pilots on their V and vettes

Submariner409
07-20-13, 08:27 AM
FuzzyLogic - Please contact CF Admin about becoming an Authorized Vendor.

FuzzyLogic
07-20-13, 08:55 AM
FuzzyLogic - Please contact CF Admin about becoming an Authorized Vendor.

I'm not selling anything (I work for an unrelated military contractor), and I receive zero compensation for any of this. This is a suspension tuning thread. Technical discussion.

Submariner409
07-20-13, 09:10 AM
Sorry for the mistake - several posts in the forum have been reported as advertising spam, have been analyzed, and you're clean. Read my PM. Thanks for the comeback.

Also, note that the other thread on suspension arms is back in business.

FuzzyLogic
07-20-13, 10:39 AM
Sorry for the mistake - several posts in the forum have been reported as advertising spam, have been analyzed, and you're clean. Read my PM. Thanks for the comeback.

That's amusing. I take it Creative Steel marked my posts as advertising spam?

Naf
07-22-13, 05:57 AM
I am in the same boat, where i am CF everywhere, except no roll cage. i have to check my spring rating, but i think i went with a 500/550, 12" front and 10" rear lengths.

I kept the rear setup pretty much like stock where the spring and shock are separate, just so i may have the widest tire possible.

I have from 450-650 in Hyperco spring ratings and in 8-12" length. So i am pretty much covered in all angles...

I dont think with a good spring brand you will need to go any higher than 600 for you have the chance to adjust the shocks more precisely.

FuzzyLogic
07-22-13, 06:52 AM
I dont think with a good spring brand you will need to go any higher than 600 for you have the chance to adjust the shocks more precisely.

I don't think you understand that springs provide constant support (i.e.: roll resistance) that shocks can never provide because they have valves and will "leak" oil past those valves during sustained G-loading.

FuzzyLogic
07-22-13, 09:45 AM
For those of you following along:

I had just enough time yesterday to install the rear, 896 in-lb springs (front springs are still stock). Since adding more spring effectively increases compression dampening but requires more rebound to control, I instinctively set compression dampening to minimum and added one click of rebound dampening. Holy s**t the car feels good-- not only is it much faster during transitions, it's COMFORTABLE! This kind of ride quality would have been flat-out impossible with FG2s and the Ground Control kit.

The net effect is that the rear feels only about 10% stiffer under bump loads, but on turns, the body confidently follows the front of the car and refuses to roll.

In summary, I unequivocally recommend that all KW Variant 3 owners get a pair of 9", 60mm, 160 N-m springs and a pair of 65mm thrust sheets. It'll be $200 very well spent.

mackey
07-22-13, 03:17 PM
noted

experiencing front end push >1G so if this cures that as well as aformentioned plushness and roll resistance, then i'm game as that's exactly what i'm looking for.

Manofmetal01
07-22-13, 11:39 PM
These are not the Swift Z60-228-140 (9" length, 784 in-lbs) that you recommended to me? Curious why you chose to run different before I throw my order in.

Naf
07-23-13, 02:39 AM
Fuzzy,

Its great you are experimenting with your spring tension.

I am chatting with my suspension guy and working it out so i can be happy on the track and on the street

FuzzyLogic
07-23-13, 07:07 AM
experiencing front end push >1G so if this cures that as well as aformentioned plushness and roll resistance, then i'm game as that's exactly what i'm looking for.

At more than 1.0G, you're going to be fighting a lot of things. I never said that the ride was plush. It's about 10% stiffer than the KW Variant 3 with KW's recommended compression dampening setting. However, it's more comfortable because the car isn't pitching and the rear isn't rolling out from behind the front of the car.

It sounds like you're assuming that your front-end push is merely due to having lower roll resistance in the rear. Please note that this issue will be exacerbated if you're on the gas through the turn, since you'll be transferring even more load to the rear. I would also look at your alignment. Make sure you zero out your toe in the front, or maybe even set it to 0.05 degrees of positive toe per wheel (0.10 degree total). Whatever you decide, add at 0.02 degree of negative toe to the passenger side front wheel to prevent the car from wanting to drift right on roads with excessive crown.


These are not the Swift Z60-228-140 (9" length, 784 in-lbs) that you recommended to me? Curious why you chose to run different before I throw my order in.

Could you refresh my memory? I don't remember when that was. I definitely recommended those springs for the guys running Ground Control kits.

To be frank, I took a risk (even though I believed my calculations) with the 896 in-lb rear springs (versus the 784 in-lb springs), because I didn't know how wide the compression valving on the KW Variant 3 opened, or how viscous the oil in the shocks was. If I recommended the 784 in-lb springs to you, it was because that was the "safe" option. First, 784 in-lb springs would have hugely reduced pitch on your car and fixed the lack of roll resistance in the rear, and second, the risk of you complaining that the ride was harsh was significantly less.

But as it turned out, with the rear shocks set to minimum compression (full open), the rear end's dynamic compression only increased by about 10%. It's comparable to a FG2/GC/600 in-lb spring. Knowing that, I can recommend the 896 in-lb springs for anyone with a KW Variant 3 kit. Your front/rear bias with the stock front springs is going to be -15%, which is smack in the middle of the 10-20% sweet spot.

barrok69
07-23-13, 10:35 AM
I thought I was the only one that liked Hankook rs3 tires on my cars. It seems like everyone uses Michelin pilots on their V and vettes

Not to threadjack, but for daily driver summer tires, the PSS's are hard to beat. RS3's are awesome on dry, but terrible in the rain. My next set of tires is going to be Bridgestone RE-11's due to Michelin not making the width/aspect ratio I'm looking for in their PSS lineup.

Manofmetal01
07-23-13, 12:01 PM
and second, the risk of you complaining that the ride was harsh was significantly less.


Haha that made me laugh. I'm not going to blame someone else for something I choose to do. Nobodys put a gun to my head and forced me to do anything.

Have you experienced and bumps while cornering? And I mean, does the stiffness cause your ass end to skip out on bumps or she holds tight?
What is your fender to wheel center measurement? I'd like to get my rear lower again if rubbing is no longer an issue.

Manofmetal01
07-25-13, 10:39 PM
Just to confirm, you went with 60mm springs but 65mm thrust sheets? This may seem like a stupid question as I'm still learning, why the difference in size? My order is almost done, the sales guy asked me why the 65mm so before I commit I figure I should understand more.

FuzzyLogic
07-26-13, 06:04 AM
Just to confirm, you went with 60mm springs but 65mm thrust sheets? This may seem like a stupid question as I'm still learning, why the difference in size? My order is almost done, the sales guy asked me why the 65mm so before I commit I figure I should understand more.

I know it's strange. 60mm thrust sheets will not fit over the KW Variant 3 spring perches in the rear. Their inner diameter is 1-2mm too small, even though the 60mm thrust sheet measures 60.45mm on the inside. Fortunately, I had a couple of 2.5" thrust sheets from my previous Ground Control builds that worked. Swift's 544202 65mm kit is also called a 2.50" kit, so even though there's a couple of millimeters of slop, I think it should work. It needs to rotate freely on the perch--otherwise all you have is a nylon ring that will help prevent metal-on-metal chatter, but nothing else.

The car still holds tight while cornering. The biggest difference is that if you drop the car into a big dip in the road at high speeds, that beforementioned +10% stiffness will feel more like the +75% that these springs are the suspension rebounds. Why? Because in those situations, the high-speed blow-off valve of the KW Variant 3 shocks opens, allowing much more oil to pass in a short amount of time (reducing compression dampening severalfold). By the way, if I take a digital caliper and go straight down from fender to the point at which I hit the rubber on the sidewall, I get 30mm. The actual tire is about 10mm taller than that, but due to its curvature, it's located further inward. Given the fact that I haven't bottomed out on some really nasty stuff, I'll probably knock an extra 5mm off this weekend, once I dial in the front end for the 672 in-lb springs.

If you're following along, I still think that there's a place for the 784 in-lb (140 N-m) spring for users that are dead-set on a plush ride. It'll give you a wider range of tuneability--you might not get as much cornering support or as strong of an undamped anti-pitch frequency balance, but you could probably fake it for about 0.5 second with additional compression. But I'd never go lower than 784 in-lbs in the back. If you're planning on increasing the spring rate in the front from the standard 574 in-lb (100 N-m) to the next size up (672 in-lb / 120 N-m), your only option is the 896 in-lb (160 N-m) rear springs.

FuzzyLogic
07-27-13, 04:12 PM
Dialed in some good settings for stock KW Variant 3 springs in the front and Swift 896 in-lb springs in the back, using the following stance:

http://img.photobucket.com/albums/v219/QuicksilverG4/CTS-V/DSC00939_web_zps5e11c183.jpg~original

Front: as specified by KW Variant 3 manual.
Rear: compression set to full soft, rebound set 5 clicks from full hard.

Known bad: full soft (wildly uncontrolled), 9 clicks from full hard (recommended by manual--uncontrolled), 3 clicks from full hard (unresponsive), and full hard (very unresponsive). Also tried 6 clicks from full hard--not bad, but just on the verge of proper control (felt a little strange). 6 clicks might work better if your car is significantly heavier in the ass than mine.

Installing the front 672 in-lb springs now. Will report back with final tunings in about a week when springs have settled and I've been able to fine tune ride heights.

Iceman_jd
07-27-13, 08:07 PM
I never liked how soft the rear spring rate is on the KW Variant 3, that being said great job on the work and info you provided. Yesterday I just order the Swift 544202 Spring Thrust Sheets Kit 65mm 2.50" and the Swift Z60-228-160 Metric Coilover (896 in-lbs). Figured I'd try it and see how I like it.




The car still holds tight while cornering. The biggest difference is that if you drop the car into a big dip in the road at high speeds, that beforementioned +10% stiffness will feel more like the +75% that these springs are the suspension rebounds. Why? Because in those situations, the high-speed blow-off valve of the KW Variant 3 shocks opens, allowing much more oil to pass in a short amount of time (reducing compression dampening severalfold).


Question Fuzzy, when talking about the high speed dip encounter feeling +75% stiffer than stock KW Variant 3 settings, (original springs and recommended shock settings) is that before you were able to get the rebound setting dialed in for the Swift 896 in-lb springs? If so now that they're dialed in how would you rate them?

Third question, with the compression set to minimum and the high-speed blow-off valve compressing causing the spring to suddenly compress, the stiffness you were talking about the initial shock of compression of the shock absorber or the uncontrolled rebound of the spring (whiplash effect) due to the shock not being dialed in as of yet?


Dialed in some good settings for stock KW Variant 3 springs in the front and Swift 896 in-lb springs in the back, using the following stance:


Front: as specified by KW Variant 3 manual.
Rear: compression set to full soft, rebound set 5 clicks from full hard.

Known bad: full soft (wildly uncontrolled), 9 clicks from full hard (recommended by manual--uncontrolled), 3 clicks from full hard (unresponsive), and full hard (very unresponsive). Also tried 6 clicks from full hard--not bad, but just on the verge of proper control (felt a little strange). 6 clicks might work better if your car is significantly heavier in the ass than mine.


Lastly is the (known bad): in reference to your experiment with dialing in the rebound settings for the rear? (I'm assuming so)

Thanks, John

FuzzyLogic
07-27-13, 09:15 PM
I never liked how soft the rear spring rate is on the KW Variant 3, that being said great job on the work and info you provided. Yesterday I just order the Swift 544202 Spring Thrust Sheets Kit 65mm 2.50" and the Swift Z60-228-160 Metric Coilover (896 in-lbs). Figured I'd try it and see how I like it.

You and at least two other people. I think you'll like it. It's all about getting the front and rear dampening settings tuned correctly. Controlling the release of energy from those Swift rear springs can store is more than within the capability of the KW Variant 3 rebound valving, but everybody's car is a little different in the weight department. One click in the wrong direction, and the car will feel a little off, so it's important to get it right. Someone other than me can try to optimize the front further than I did, which may affect the rear tuning, but I think that that will be in the realm of custom-tailoring the response to the car to your individual tastes.

For instance (http://forums.nasioc.com/forums/showpost.php?p=1535904&postcount=4):

"Increasing front rebound damping and increasing rear compression will hold the nose of the car down and the rear of the car up longer after braking, which will help turn-in response if your car is having turn-in understeer. The effects don't last long though, and it will not affect steady state cornering. Softening front rebound and softening rear compression will allow a quicker weight transfer to the rear, getting the rear end to plant itself quicker, letting you get on the gas harder, sooner. But this is opposite of the first example and will affect turn-in. Shock tuning is very complicated and people that are experts at it get paid VERY well."


Question Fuzzy, when talking about the high speed dip encounter feeling +75% stiffer than stock KW Variant 3 settings, (original springs and recommended shock settings) is that before you were able to get the rebound setting dialed in for the Swift 896 in-lb springs? If so now that they're dialed in how would you rate them?

Prior to dialing in the rebound setting. That earlier impression was based on the rear rebound at 9 clicks softer than full hard (default KW tuning). What I was feeling was actually the upstroke after the car landed--a powerful (barely controlled) expansion of the springs to their original height. No huge overshoot and oscillation, though. However, if you were to take that same exact situation, but set the rear shocks to minimum rebound dampening (as I did), you would get an overshoot and subsequent oscillation.

I haven't had enough time in the car at 5 clicks to give you a "X% stiffer" number yet, but the response is pretty good. The return to nominal height is fast, but controlled. I felt that 3 clicks dampened the movement of the shock so much that its dampened frequency no longer correctly caught up to the front end.


Third question, with the compression set to minimum and the high-speed blow-off valve compressing causing the spring to suddenly compress, the stiffness you were talking about the initial shock of compression of the shock absorber or the uncontrolled rebound of the spring (whiplash effect) due to the shock not being dialed in as of yet?

The latter. See above.


Lastly is the (known bad): in reference to your experiment with dialing in the rebound settings for the rear? (I'm assuming so)

Correct.

FuzzyLogic
07-28-13, 09:10 PM
Quick update: with 5 clicks, the car feels effing awesome. I beat the living crap out of the suspension on some awesome New England twisties and I dare say that a girl wouldn't mind the ride. Iceman, to your percentage question from earlier: the answer is a little more than 25%. Sadly, I didn't have time to add the 672 in-lb front springs this weekend (just drove the crap out of it).

Plans for upcoming week and weekend: Banski RSM design finalization, installation and tuning for 672 in-lb front springs.

Following week: fine-tuning of ride height, aggressive alignment, upgraded power steering cooler, and silver V2 6-piston brake calipers.

sssnake
08-07-13, 03:37 PM
Keep us posted. I am interested in where you end up with these. I will likely be adapting your solution.

Any suggestion about where to get actual corner weights? I am not having a lot of luck here and purchasing scales myself is out as the cheapest I found were over a grand. I would use your assumptions but with the blower on the front and a large stereo and battery relocate to the back I am likely a good bit different than stock.

I forgot to mention - Kick ass post.

FuzzyLogic
08-18-13, 09:58 AM
Quick update: for the 674 in-lb front springs, my initial estimate of full soft compression and 50% additional rebound dampening (8 clicks from full hard) is working pretty well.

Haven't been able to really beat on the car because I need to get an alignment. Had to remove the front control arm to install new bushings. Suspect that final tuning will involve somewhere between 1/4 and 5/4 turns additional compression dampening (front and rear) to sharpen up the handling. Will report back with final-ish tuning figures.

Naf
08-18-13, 12:50 PM
I like ur enthusiasm but i feel too stiff of a spring will rattle ur brain.

I will be runnin on 550 up front and 525 in the rear.

I had 475 with 500 but it was a bit too comfy.

Hyperco are great, but the color needs work.

Hopefully by this weekend i can be done with the oil tank and move forward by startin my little monster...

FuzzyLogic
08-18-13, 01:35 PM
I like ur enthusiasm but i feel too stiff of a spring will rattle ur brain.

I will be runnin on 550 up front and 525 in the rear.

I had 475 with 500 but it was a bit too comfy.

Hyperco are great, but the color needs work.

Hopefully by this weekend i can be done with the oil tank and move forward by startin my little monster...

Are we talking about the same suspension? The 672F/896R KW Variant 3 is pretty comfy.

Manofmetal01
08-18-13, 06:56 PM
Springs and thrust sheets are heading my way via fedex tomorrow!! Excited

FuzzyLogic
08-18-13, 07:00 PM
Springs and thrust sheets are heading my way via fedex tomorrow!! Excited

Which ones?

You (and everybody else here) should know that the KW Variant 3 spring perches run a millimeter or two large. So the Swift springs are going to be a very tight fit and won't rotate until they've broken in around the ring. Apparently, it's a well-known fact to the suspension experts out there, which I didn't pick up on until I tried installing (gasp!) a 60mm thrust sheet on the 60mm KW V3 perch and a 70mm thrust sheet on the 70mm KW V3 perch.

Had to spend 30 minutes dremeling out each set of rings with a grinding tool I bought at Home Depot. A 65mm thrust sheet will work on the back perch, but nobody sells 75mm thrust sheets. So you'll have to dremel at least one set if you want thrust sheets.

Manofmetal01
08-18-13, 09:03 PM
Z60-228-160 with 65mm thrust sheets as per your recommendation. I won't be installing them until I get my trailing arms, toe rods, tie rods, rms mounts and revshift bushings. Ill do it all at once.

FuzzyLogic
08-18-13, 11:41 PM
Z60-228-160 with 65mm thrust sheets as per your recommendation. I won't be installing them until I get my trailing arms, toe rods, tie rods, rms mounts and revshift bushings. Ill do it all at once.

That's going to be a five-day job unless you're willing to work 15 hour days, you have a press, and/or you have a proficient helper. I can't overemphasize how hard and time-consuming it is to remove the stock bushings. Until you know otherwise, budget an entire day for the subframe and control arm bushings. Take Friday afternoon off and concentrate on totally disassembling the rear end of the car by the end of the day.

Manofmetal01
08-19-13, 12:21 AM
I work the drilling rigs, I have a week off at a time so ill manage. Ill figure it out when I've got all the parts ready to go. Youre install posts will be invaluable

Naf
08-19-13, 01:06 AM
Ahhh, i am runnin penske style shocks, that could be the reason behind ur high spring rates.

As i said before, u need a little give so u may shift the weight forwards and backwards...

Iceman_jd
08-20-13, 12:06 AM
Which ones?

You (and everybody else here) should know that the KW Variant 3 spring perches run a millimeter or two large. So the Swift springs are going to be a very tight fit and won't rotate until they've broken in around the ring. Apparently, it's a well-known fact to the suspension experts out there, which I didn't pick up on until I tried installing (gasp!) a 60mm thrust sheet on the 60mm KW V3 perch and a 70mm thrust sheet on the 70mm KW V3 perch.

Had to spend 30 minutes dremeling out each set of rings with a grinding tool I bought at Home Depot. A 65mm thrust sheet will work on the back perch, but nobody sells 75mm thrust sheets. So you'll have to dremel at least one set if you want thrust sheets.

I spent around an hour today hand fitting the 896lb Swift springs to the four KW V3 rear spring perch. :suspense: Will finish the job tomorrow with the install of the spherical shock mounts.

FuzzyLogic
08-20-13, 10:56 AM
I spent around an hour today hand fitting the 896lb Swift springs to the four KW V3 rear spring perch. :suspense: Will finish the job tomorrow with the install of the spherical shock mounts.

You probably didn't have to muscle it...just get each spring centered and let the vehicle weight do the rest.

Iceman_jd
08-20-13, 06:42 PM
You probably didn't have to muscle it...just get each spring centered and let the vehicle weight do the rest.

Probably but if I forced it what's the point of the thrust sheets if the spring is binding on the perch. At least now the springs are able to rotate freely within the KW3 spring perches.

FuzzyLogic
08-20-13, 06:55 PM
Probably but if I forced it what's the point of the thrust sheets if the spring is binding on the perch. At least now the springs are able to rotate freely within the KW3 spring perches.

Any driving impressions yet? I'd love to hear what you've got, whether negative or positive.

Iceman_jd
08-20-13, 10:56 PM
Any driving impressions yet? I'd love to hear what you've got, whether negative or positive.

Yeah got a little side tracked today going to hit it hard tomorrow, will keep you informed when job is complete and impressions formed.

mackey
08-21-13, 12:11 AM
best place to pick up the swift springs and thrust sheets?

Manofmetal01
08-21-13, 01:01 AM
best place to pick up the swift springs and thrust sheets?

I just checked their distributor page and went with one of them.

FuzzyLogic
08-21-13, 06:58 AM
best place to pick up the swift springs and thrust sheets?

MAPerformance for the springs, FRSport for the thrust sheets. I don't have the receipt with me, but I believe I paid $85 or $80 per spring.

Iceman_jd
08-21-13, 04:49 PM
Finally finished installing the 896lb Swift springs and spherical RSM. Compression set to minimum, rebound set 3 clicks minus from max setting.

Springs pre-loaded to zero lbs, just to the point of rattle loose. With that setting my ride height is 26.25" from the ground to fender lip.

To get it any lower I was thinking (Big mistake) if it was possible to do a mighty mouse type setup with the mounting plate on top. That should raise the lower control arm to make up the difference of the shorter swift spring and giving greater range of height adjustment (to the lower side).

Putting that aside quick test ride was pretty sweet, I thought it turned pretty quick before, now it seems very tight with very little steering lag. Just point and shoot. The rear feels a little stiffer but not in a bad way just more planted. Overall I would recommend this mod.

FuzzyLogic
08-21-13, 05:44 PM
Try 5 clicks. Compare it with 3 clicks. Overdoing the rebound dampening is not a good thing--you're unnecessarily limiting the rebound rate of the springs.

Iceman_jd
08-21-13, 06:16 PM
Try 5 clicks. Compare it with 3 clicks. Overdoing the rebound dampening is not a good thing--you're unnecessarily limiting the rebound rate of the springs.

Thanks Fuzzy will back off rebound damping 2 clicks.

mackey
08-21-13, 11:55 PM
not finding the springs on map

FuzzyLogic
08-22-13, 01:12 AM
not finding the springs on map

That's because you have to call them.

Iceman_jd
08-28-13, 02:34 PM
Rear spring is done with spherical RSM and shocks adjusted per Fuzzys recommendations. The handling is great and the ride quality is very good. Front springs and poly suspension bushings next.

Anyone else finish the spring/springs change? Manofmetal01 how's the spring/ bushing install going?

Manofmetal01
08-29-13, 04:05 AM
Springs just arrived a few days ago but I'm waiting on more parts...and now I need a new rear tire...oops

CTSVLSX
08-29-13, 06:28 PM
I'm waiting on the RSM's and ordering some springs. I was curious about the specs of Fuzzy's entire setup, which exact springs and thrust sheets on the back/front what the shock settings are etc. I want to use that as a baseline and tune from there. Trying to glean all the information from these threads is tedious :)
If we could come up with a baseline for KW3 shocks that would be great. 896 rear 600 something front? what size springs and length and what clicks adjustment and height.
After I get a good baseline will do the alignment aggressively..
Maybe start another thread with different shocks/springs combos and some good baseline settings?

I'm still looking for someone with a corner weight machine in south florida..

FuzzyLogic
08-29-13, 07:23 PM
If we could come up with a baseline for KW3 shocks that would be great. 896 rear 600 something front? what size springs and length and what clicks adjustment and height.

Maybe start another thread with different shocks/springs combos and some good baseline settings?

Honestly, the 574/896 combination is pretty nice. If you're looking for a comfortable, baseline KW Variant 3 build that can perform, it's not a bad place to be. It's probably more appropriate for CTS-Vs that are closer to stock.

I'm still working out the kinks on the 672/896 setup. I'm giving it a lot more attention than I did the 574/896 setup (which was only on the car for two weeks because I couldn't find the time to do all four corners on Day 1), factoring in end link lengths, ride height, corner weight, alignment, and so forth. Once I'm done, I'll type it all up for you to play with.

CTSVLSX
08-29-13, 08:54 PM
Awesome, ty! Mine is nowhere near stock lol.. In fact it has a LSX replica RHS block in it 430 cid and pretty much everything else I could do to it except appearance mods which I will do later.
I really don't care that much about the ride being 'comfortable' as long as it's not teeth rattling going down a normal street that doesn't have any major defects. High speed stability and cornering is what I'm looking for. Planning on tracking it eventually but I'm having a heck of a time finding someone with a corner weight machine in palm beach county FL. Guess will have to do the old fashioned way by measuring the height or rolling each wheel up on something individually which skews balance a bit but might have to be done.

Most of the mods i have are the same ones listed in your signature aside from me swapping out my entire engine, and I sent the trans to liberty to get beefed up, and I have the geforce 9" IRS rear with 2 piece driveshaft. Nitrous is next on the list for a cool 1000HP

odla
09-02-13, 12:17 AM
I know of a place in Miami that can corner weigh the car.

Manofmetal01
09-14-13, 07:37 PM
The springs are in, I couldnt wait for the other parts to arrive. I haven't adjusted the rebound rate etc yet as the other parts will be here soon and ill do that then. I did manage to take about 3/8" out of the rear ride height with no issues yet. Looking forward to fully dialing this in but so far so good.

FuzzyLogic
09-14-13, 07:47 PM
The springs are in, I couldnt wait for the other parts to arrive. I haven't adjusted the rebound rate etc yet as the other parts will be here soon and ill do that then. I did manage to take about 3/8" out of the rear ride height with no issues yet. Looking forward to fully dialing this in but so far so good.

If you don't adjust the compression rate, the rear end will feel like a rock.

Manofmetal01
09-14-13, 07:57 PM
I will adjust. The other parts should be here monday. I can wait till then. Not running her hard. Just been detailing and stuff.

Manofmetal01
09-19-13, 09:39 PM
Made the adjustments...feels..well lovely really. I took a little chunk out of my new tire on a bump I didn't see in time. I think ill raise that side a hair and roll my fenders to prevent this in the future...last time that was a $500 oops..

Manofmetal01
10-05-13, 03:44 PM
Fuzzy, since doing your suspension mods, have you found it much easier to kick the ass end out and hold it there through 2nd and 3rd? I feel I have much more control now as to were I want the rear...coming out of corners sideways is almost natural now. Needless to say the car is even more a pleasure to drive, thanks for your hard work!

FuzzyLogic
10-05-13, 04:39 PM
Fuzzy, since doing your suspension mods, have you found it much easier to kick the ass end out and hold it there through 2nd and 3rd? I feel I have much more control now as to were I want the rear...coming out of corners sideways is almost natural now. Needless to say the car is even more a pleasure to drive, thanks for your hard work!

You're very welcome. I'm glad that you're enjoying the car more now. Us redline/infrared CTS-V guys have to stick together--and remind people that red cars always go faster! ;)

The additional control you're describing is likely the result of being in the "sweet spot" between having maximum mechanical grip and control. With the original KW Variant 3 springs and settings, I felt that the car would just tilt/roll away from whatever I was doing, which was great for traction (until the outside tires let go), but made it difficult to wrest control away and point the car in the fastest direction. Mechanical grip is great to a point--you can't run fast when your feet are glued to the floor. :thumbsup:

FuzzyLogic
10-15-13, 09:30 PM
Update: I cut another slice off the Supra end link rod.

This tweak shortened the end link to the point where both nuts would *almost* be in contact with the arms of the end link, but still free to twist to follow the movement of the bar. The reason why I felt this was necessary was that my previous settings (http://ls1tech.com/forums/17739173-post36.html) were too long to activate the sway bar when I wanted them to. I may shorten the end link further in the future, but I'll need a week or so to test.

http://i1345.photobucket.com/albums/p663/Fuzzylog1c/Suspension%20Tuning/DSC01616_zpsfb5b3f7f.jpg (http://s1345.photobucket.com/user/Fuzzylog1c/media/Suspension%20Tuning/DSC01616_zpsfb5b3f7f.jpg.html)

If you decide you want to do this, just ensure that you cut the threaded rod to a length equal to or less than 54mm.

FuzzyLogic
10-16-13, 11:34 PM
Great question, reprinted from LS1Tech:


I was under the impression that adjustable end links were used to dial out preload in the sway bar when corner balancing the suspension. I suppose if adjusted in extreme amounts in tandem, the pair could change the bars effective stiffness through geometry, but I'm missing how they would affect when the sway bar activates.

It's true that end links can be used to dial-out preload.

The lesser-known fact (which, ironically, I consider more important) is that end link geometry determines how effective your sway bar is at canceling out body lean. Depending on your background, it might be hard to picture this without drawing force body diagrams. If you're willing to take my word for it, the nominal end link and sway bar geometry is pictured below:

http://honda-tech.com/attachment.php?attachmentid=120089&d=1270653263

Under nominal conditions, any differential compression or expansion of the vehicle's suspension (e.g. imagine the LCA in the picture above moving up or down) will transfer that force to the other side of the car through the sway bar. Notice how this is force is actually torque (T = r x F), as it is applied perpendicular to the axis of rotation of the sway bar.

The force transfer is not 1:1--the sway bar twists under the torsion, acting like a massive straight spring, and reduces the degree to which load is shared between the sides of the vehicle. If the end links are too long or too short, the resultant, non-ideal geometry reduces the amount of the force that directly translates to torsion on the sway bar. What's left is not perpendicular to the axis of rotation of the sway bar, and essentially tries to rip the sway bar out of the car.

http://craig.backfire.ca/img/torque-force.png

Unfortunately, this nominal geometry is very hard to achieve in modified vehicles--usually because the suspension geometry has changed due to lowering the vehicle. However, this can also happen to vehicles at stock height, because some aftermarket suspension parts do not match the OEM suspension geometry.

philistine
10-17-13, 12:03 AM
Put away your cheetos...there will be a test after viewing this, please show all your work.



JFWY, good info

FuzzyLogic
10-17-13, 01:21 AM
Put away your cheetos...there will be a test after viewing this, please show all your work.

After correcting for the slope of my parking spot, I measured 88 degrees, fore-aft, using my level gauge (http://www.amazon.com/gp/product/B007VRBCTI/ref=ox_sc_act_title_1?ie=UTF8&psc=1&smid=A30XU5Y510T9EB). Since my setup is far from ideal (despite my attempts to correct for it), I'd give my measurement a generous 5 degree margin of error. Still, that's pretty good. No picture, unfortunately--I couldn't get my camera, head, and gauge into a good position.

http://i1345.photobucket.com/albums/p663/Fuzzylog1c/Suspension%20Tuning/DSC01621_rotated_zps5c9d0ac4.jpg (http://s1345.photobucket.com/user/Fuzzylog1c/media/Suspension%20Tuning/DSC01621_rotated_zps5c9d0ac4.jpg.html)
Athwartships angle with the wheels off the ground. This angle is set by the length of the sway bar. No possibility of improvement.

http://i1345.photobucket.com/albums/p663/Fuzzylog1c/Suspension%20Tuning/DSC01634_zps311690e9.jpg (http://s1345.photobucket.com/user/Fuzzylog1c/media/Suspension%20Tuning/DSC01634_zps311690e9.jpg.html)
Angle on the sway bar with the wheels off the ground. Will try to get one with the wheels on the ground later. Whiteline KLL135 and KLL127 link locks are necessary on the Addco bars to maintain the athwartships angle identified in the previous picture. Hotchkis bars come with welded stops that prevent the bar from sliding, so you don't need aftermarket locks.

http://i1345.photobucket.com/albums/p663/Fuzzylog1c/Suspension%20Tuning/DSC01537_zps2eac5f01.jpg (http://s1345.photobucket.com/user/Fuzzylog1c/media/Suspension%20Tuning/DSC01537_zps2eac5f01.jpg.html)
http://i1345.photobucket.com/albums/p663/Fuzzylog1c/Suspension%20Tuning/DSC01527_zpsf52fa92a.jpg (http://s1345.photobucket.com/user/Fuzzylog1c/media/Suspension%20Tuning/DSC01527_zpsf52fa92a.jpg.html)
I almost gagged on a Reese's Peanut Butter cup when I saw this picture in its full, 24 megapixel glory. Proof that both sway bars slid back and forth a lot. Check out the clean-ish areas next to the brackets.

raguncajn
10-20-13, 06:17 PM
After having 2 blown front shocks for a year I finally decided to upgrade the suspension. I picked up the Belltech kit for $1800 + shipping from ebay. If anyone has any doubts that it is not a KW kit see the pictures below of what I received.

https://lh5.googleusercontent.com/-9DCyENcULo4/UmPe4Gal6wI/AAAAAAAAC_g/Gj6d7pUu_BU/s800/2013-10-19%2525252020.53.38.jpg

https://lh4.googleusercontent.com/-AT0sPFlobNA/UmPe4i_qHBI/AAAAAAAAC_o/tjwEaCD3q0c/s800/2013-10-19%252020.53.21.jpg

It's like Christmas morning!:)
https://lh6.googleusercontent.com/-QPtqbjvBIro/UmPn6-_Pm5I/AAAAAAAADAA/qzRBVHswJeA/s800/2013-10-20%252009.23.10.jpg

Thanks to FuzzyLog1c for all the great info. I am going with your setup of springs, sways, and even the hotchkis brackets. I went with powergrid endlinks though. I also ordered the Banski shock mounts, revshit cradle bushings, and control arm bushings. I have killernoodle trailing arms already, and Creative Steel toe rods are on the way. I can't wait to get all this installed and feel the difference!