: Advice on suspension setup - Track + lowering = GC?



MrAceman
05-25-09, 12:45 AM
Just bought an 04 CTS-V with modded LS7 swap and Madman Racing Ford 9 inch rear end. It used to belong to VDiddy here on the boards.

I've been looking at upgrading the suspension to allow for some track related work. It's got a full front and rear Hotchkiss anti-sway bar setup but I'd like to stiffen the suspension a bit (just more used to the go-kart type feel of my WRX) and also would like to drop it a little.

The Hotchkiss stuff is the only suspension modification... besides that it's got the standard FE4 suspension in it.

From everything I've been reading it's looking like the Ground Control are the way to go on the spring side... for my case probably the "hot rod caddy 10%" setup unless anyone with the "track day/auto-x 25%" thinks that this setup would still be doable as a daily driver.

Again, I'm used to a "feel every bump in the road" type car and don't mind it at all... especially if it gives me better handling. I'm looking to do some HPDE and engage in spirited driving (legally, of course!) most of the time anyways. Also keep in mind that with the custom exhaust this car is already loud enough to wake the dead at idle so it shook off it's "luxury sleeper" mantle a while back. I'm actually even examining the option of swapping out the custom mufflers with Magnaflow mufflers... just to quiet it down a little. It's nutty loud. :bonkers:

Do you guys think my FE4s are good enough to keep or should I pursue a different avenue there? I know I can drop the ride hight with those but I just wanted to make sure they would still work if I went with the +10% or +25% GC setup. Would love to be able to save some $$$ by just getting the GC, but if the stiffer springs aren't going to work with the FE4s then I'm open for advice.

Thanks!

DisposableHero
05-25-09, 06:38 AM
im interested too

Twitch
05-25-09, 08:15 AM
People say that the FE4s aren't stiff enough to handle it. I don't know for sure, cuz I swapped out everything at the same time. It all has to come out anyway, so you might as well do both now.
Look up "feffman fix" for the GC install. You need to add some washers to the rear.
When you lower the car, the front Hotchkis bar gets very close to the shock. Sometimes hitting it. A few current threads on it. Check them out.
You'll also need C5 Z06 endlinks. Get them from Luke @ Lyndsay Cadillac.

SoJersey05V
05-25-09, 10:30 AM
i have stock car and i just ordered QA1 shocks (single adjustable) with GC kit. i think the street performance is a 500/550 setup with the springs... i went 600/650, now im not sure if that is their "hot rod caddy" setup or not so i just wrote it in at the bottom what i wanted.


***qa1 owners... am i going to have to do this feffman fix on the qa1's or no? want to know b4 i start this install.. thanks*****

tweeter81
05-25-09, 10:13 PM
See my sig for suspension mods. My car handles like it's on rails. I actually now have Toyo R888s (235/35zr19 and 295/30zr19) and it sticks like super glue. These car handle very well in stock trim, but you can make them really sweet with cheap mods like you have discussed above.

MrAceman
05-26-09, 03:08 PM
Thanks for the advice so far...

Called Luke at Lindsay and Drew at Hotchkis and have the C5 Z06 endlinks and anti-clunk kit otw to prep my car for the new suspension.

My next question is this... since I've got totally stock suspension (besides the Hotchkis) I'd be looking at about $500 for the GC and $1k for the QA1.

Instead of spending $1500+ for that how much of a performance upgrade do you think I'd be looking at by saving up for a couple months and going with the KW coilover setup ($2300). All these prices are based on the d3cadillac and GC websites.

$2.3k is a good bit to spend on suspension, but this car is really beyond modding for power unless I get a maggie down the road for somewhere north of 700rwhp... of course then I'd need a viper spec tranny as well so I'm just gonna stick to mods that make it more trackable.

So... $1500 for QA1 + GC or $2300 for KW coilover?

MrAceman
05-26-09, 03:13 PM
Let's put this last question on hold as I'm finding that my prices are WAY higher than they should be. ;)

And BTW... how do you like my shiny new banner? I knew something was missing from my modding plan. Gotta support the site that you use to justify the spending :)

MrAceman
05-26-09, 04:02 PM
Looks like I'd be looking more like ~$1.5k for the QA1/GC combo (or is that still high?) and ~$2k for the KW.

Either option is still pricey... guess I'm wondering if the difference is big enough and/or the extra customizability is worth it.

SoJersey05V
05-26-09, 08:06 PM
$1000 for qa1s????? dont buy from d3, they are too high and dont return emails... got mine from new era $804 shipped... i can supply you with part numbers to use if need be... matter of fact Jegs has the qa1s for cheaper then d3...

you'd think they would help out the caddy crews and have a more competitive price... no bashing (your body kits look great) but prices for same parts are way too high.

MrAceman
05-28-09, 12:26 AM
Ok now... this is getting a little more of a better debate.

QA1/GC for $1300 vs KW for $2k.

I am determined to make my V more trackable than my friend's C5 Z06. And I drove his Z06 and know it's a tall order. I'd already got him hands down in the power department. However he'll be running R compound 275s in the front and 315s in the back so I need all the handling help I can get since I'll probably have my 245 shoes on the first time out.

thebigjimsho
05-28-09, 02:27 AM
You'll never be able to outhandle a car that's more than 600lbs less than the V and sits so much lower. But you can certainly make it better. Let me give you my experiences.

I started with FE4s and stock springs. Went to FG2 and found them overdamped for the stock springs even though it was a factory option. Eventually went to FG2 and 500/550 Ground Controls. Absolutely loved the combo. Perfectly matched for each other. Definitely firmed up but still a smooth ride for very long distances. The only issue, I believe, is that the FG2's life is shortened when dropped over time. QA1s certainly don't have as much a problem since they can be rebuilt almost anywhere.

I just installed QA1s with stiffer springs on my Ground Controls. I went 650/700. I'm not thrilled with the combo. I'm getting way too much jounce when the QA1s are set to softer and they have to set very firm to help that. Even then, I still get a lot of squat on big dips. So I'm going to try 500/550 again. My QA1s were bought used and may have been rebuilt to different specs so I need to sort that out.

What I loved about the GC 500/550 springs was that it worked so well on the street but also the track. And the V's suspension need not be so firm to really respond. That's also the great thing about GCs. You can always buy firmer springs if you feel the need.

MrAceman
05-28-09, 12:24 PM
You'll never be able to outhandle a car that's more than 600lbs less than the V and sits so much lower.

HOGWASH!!!

Thanks for the advice... I think I am leaning more towards the QA1/GC setup if only for the cost savings, although I'm thinking of going with the slightly firmer setup.

SoJersey05V
05-28-09, 02:06 PM
i just got my qa1's last nite and am expecting the 600f/650r gc tomorrow.

DisposableHero
05-28-09, 05:56 PM
You'll never be able to outhandle a car that's more than 600lbs less than the V and sits so much lower. But you can certainly make it better. Let me give you my experiences.

I started with FE4s and stock springs. Went to FG2 and found them overdamped for the stock springs even though it was a factory option. Eventually went to FG2 and 500/550 Ground Controls. Absolutely loved the combo. Perfectly matched for each other. Definitely firmed up but still a smooth ride for very long distances. The only issue, I believe, is that the FG2's life is shortened when dropped over time. QA1s certainly don't have as much a problem since they can be rebuilt almost anywhere.

I just installed QA1s with stiffer springs on my Ground Controls. I went 650/700. I'm not thrilled with the combo. I'm getting way too much jounce when the QA1s are set to softer and they have to set very firm to help that. Even then, I still get a lot of squat on big dips. So I'm going to try 500/550 again. My QA1s were bought used and may have been rebuilt to different specs so I need to sort that out.

What I loved about the GC 500/550 springs was that it worked so well on the street but also the track. And the V's suspension need not be so firm to really respond. That's also the great thing about GCs. You can always buy firmer springs if you feel the need.

can you let us know how the softer springs compare to the 650/700 with the qa1s? thx

MrAceman
06-20-09, 10:29 PM
Road Atlanta was a blast but the FE4s have GOT to go. Same thing goes for the street tires. I was able to pull 1.17 right and 1.11 left (according to the magical dash computer) with my setup through the big sweepers (probably turns 12 and 1, both right handers) but still was seriously overloading my front left through those and the weight transfer back and forth from 2 through 5 including "The "Esses" made my instructor comment how nice and cushy the SUV suspension on my 4000lbs car was.

I'd like to make a decision on this and found the KW coilovers for just under $1800 on gripmotorsports.com ($1734 + 60 shipping)

I seem to recall reading somewhere in the forums that with the KW coilovers you could adjust camber as well... although honestly I fail to see how that is possible. IF you can then that would seal the deal since it would allow me to run an aggressive racing camber when I'm on my Hoosier R6s (cheap used race slicks fortehwin!) and dial it back so that I don't destroy my street tires.

Anyways, I need to do something. My friend's Z06 could BARELY stay ahead of me... and he was on R-comps. With my R6s and better suspension I will decimate him... and that's what "fun" HPDE track days are all about, right?

thebigjimsho
06-20-09, 10:51 PM
Just don't buy used QA1s...

darkman
06-20-09, 11:20 PM
I'd like to make a decision on this and found the KW coilovers for just under $1800 on gripmotorsports.com ($1734 + 60 shipping)



I have been looking at suspension options including KW coilovers. The downside of the KW coilovers is that lots of folks want to sell them in sets of 4, but no one wants to: (a) sell them individually; or (b) service or rebuild them. Thus, if one of them fails your only practical remedy is to another entire set.

MrAceman
06-21-09, 01:03 AM
I have been looking at suspension options including KW coilovers. The downside of the KW coilovers is that lots of folks want to sell them in sets of 4, but no one wants to: (a) sell them individually; or (b) service or rebuild them. Thus, if one of them fails your only practical remedy is to another entire set.

That's a valid point. I've got to think that there's someone out there that can service these individually... sounds like a niche for some enterprising entrepreneur. Even if you had to ship them to Germany and have KW do it.

tbjs... unfortunately it sounds like there's a story behind that. :(