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2004-2007 Cadillac CTS-V Performance Mods Discussion, CTS-V Suspension Tuning in Cadillac CTS-V Series Forum - 2004 - 2007; Originally Posted by FuzzyLogic and second, the risk of you complaining that the ride was harsh was significantly less. Haha ...
  1. #31
    Manofmetal01's Avatar
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    Quote Originally Posted by FuzzyLogic View Post
    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.

  2. #32
    Manofmetal01's Avatar
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    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.

  3. #33
    FuzzyLogic is offline Banned
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    Re: CTS-V Suspension Tuning

    Quote Originally Posted by Manofmetal01 View Post
    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.

  4. #34
    FuzzyLogic is offline Banned
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    Re: CTS-V Suspension Tuning

    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.

    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.

  5. #35
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    Re: CTS-V Suspension Tuning

    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.

    Quote Originally Posted by FuzzyLogic View Post

    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?

    Quote Originally Posted by FuzzyLogic View Post
    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

  6. #36
    FuzzyLogic is offline Banned
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    Re: CTS-V Suspension Tuning

    Quote Originally Posted by Iceman_jd View Post
    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:

    "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."

    Quote Originally Posted by Iceman_jd View Post
    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.

    Quote Originally Posted by Iceman_jd View Post
    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.

    Quote Originally Posted by Iceman_jd View Post
    Lastly is the (known bad): in reference to your experiment with dialing in the rebound settings for the rear? (I'm assuming so)
    Correct.

  7. #37
    FuzzyLogic is offline Banned
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    Re: CTS-V Suspension Tuning

    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.

  8. #38
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    Re: CTS-V Suspension Tuning

    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.

  9. #39
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    Re: CTS-V Suspension Tuning

    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.

  10. #40
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    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...

  11. #41
    FuzzyLogic is offline Banned
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    Re: CTS-V Suspension Tuning

    Quote Originally Posted by Naf View Post
    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.

  12. #42
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    Springs and thrust sheets are heading my way via fedex tomorrow!! Excited

  13. #43
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    Re: CTS-V Suspension Tuning

    Quote Originally Posted by Manofmetal01 View Post
    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.

  14. #44
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    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.

  15. #45
    FuzzyLogic is offline Banned
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    Re: CTS-V Suspension Tuning

    Quote Originally Posted by Manofmetal01 View Post
    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.

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