DrkPhynx

Not really sure how to go about describing this, or tracking it down.

If I come up to a turn fairly quick and snap the car into the turn, the rear end feels unplanted and loose. It's a little disconcerting. It did this stock too, and I chalked it up to shocks and rubber bushings in the PHB. But it still does it.

Once the car takes a set in a steady state corner it hangs on, but it's the transition that really feels unsettled. And sometimes you can't gently ease in, but have to just go, especially in switch-backs.

If I drive along at 40-60mph on a straight road and quickly move the wheel side to side a couple times to "rock the boat", as it were (with nobody around me, obviously), the car seems to yaw, almost as if it's swinging on the tires, and it takes a little while for this to subside after I stop doing that.

I have a 2002 Trans Am WS6 with SLP SFCs welded in and an SLP STB bolted on. I have 4/3 Koni's installed, along with a DA UMI PHB, and replacement rotor blanks (to get rid of the warpage on the stock ones).

The parts were all bought new, as was the car. It has 11,8xx miles on it, all by me, and basically all babied (a little back roads fun here and there, but no racing action). SFCs went on at 4000 miles, which were SUPER-babied as I wanted the chassis as fresh as possible when putting them on (paranoid and I want this to last forever, even though I know now I didn't really need them as bad as I thought I did, I didn't know that at the time)

The Koni's were installed with the front lower perch and rear heater hose mods.

Tires were replaced with BFGoodrich gForce's in the stock size.

I've re-checked the torque on the PHB many times and know it's good. The shocks are set at full soft in the rear, and 4 sweeps from full stiff in the front. Several pressures have been tried. I can't remember them all. Right now it should be at 34f/32r, or maybe even 34f/30r. I've gone lower, higher, and with a wider spread (not that I think a wider spread would be good, just sayin') and nothing has changed.

For reference, my 1988 GTA hardtop with 88,xxx miles on it, all stock, bought used, with larger sidewalls and of course the rubber bushings in the PHB, did not do this. Granted, that was about 1998 when I sold that car, but I now have a 2003 Dakota R/T extended cab, bone stock, on 255/55R17 GY Eagle RS-As (which to my knowledge are a softer, lower grade tire than the stock WS6 tires), and it does not do this either. When I "rock the boat" on the truck, it feels solid, if I move the wheel more violently, it changes direction like a football player running through the tires. No slop, no yaw oscillations, nothing, and it stops when I stop.

Anyone have any idea what might be going on here?

Manic Mechanic

iTrader: (3)

What is the "front lower perch" mod? Have you rechecked the front shock mount bolts torques? What about the rear shocks set on full soft, that sounds counter productive to what you want to get rid of?

Vernon

Luder[PAK9]

Konis have two perch locations for the front springs: stock and .5" lower. The front perch "mod" means he set the perch to the lower location. Really shouldn't affect the suspension geometry.

And full soft is the recommended setting for Konis in the rear.

DrkPhynx

I checked the R/T last night and verified what I had suspected (but just never checked on) - the truck does not have a PHB, and is using leaf springs.

That's even more depressing - a 4000-some-odd pound pickup truck with a heavy lump of iron up front, worse f/r weight balance, and just as much (if not more) rear unsprung weight, and *leaf springs*, handles better than my car.

The car has more total grip, and better braking, but as it's not as confidence inspiring, it's not used to it's fullest potential.

I drove the truck last night and took the car in to work today, when I "rock the boat" in the truck, it's lightning quick in response, it goes where you point and if you get violent it'll throw you around, and it *stops* when you stop. With the car there is a delay before anything happens, it moves slowly, and goes through a couple oscillations when you stop. There is definitely a diffrence, and I want to cure the car of this problem.

Old Geezer

iTrader: (3)

"The shocks are set at full soft in the rear"
Tried setting them any other way??

DrkPhynx

Admittedly, I have not.

As I said, this was the case when the car was brand new too, and I was led to beleive it was the DeCarbons. I had the full soft setting recommended to me by many, many people here (including Sam Strano, who I bought the parts from), so I never thought that might be the problem. I could try it, but as I said, since it did it before.... I'm led to beleive it's something else.

Any other thoughts?

Sunset01SS

iTrader: (4)

Do you have stock lower control arms? If so I'd get aftermarket boxed or at least tubular. And I'd also experiment with harder shock settings.

My friend's Firebird felt kinda like it was floating on the highway and we finally noticed that one of the stock LCAs had snapped in two

Luder[PAK9]

That would only increase his risk of snap oversteer, unless he gets rod-ended LCA ($$$).

DrkPhynx

Yes, I do have stock LCAs, however, aren't LCAs supposed to absorb thrust and braking forces? Lateral forces are supposed to be absorbed by the PHB (and torque by the torque-arm), right?

In that case, I don't see what difference boxed LCAs would make, other than to potentially cause bind unless I get rod-ended ones, which is what I'm guessing Luder was referring to. And I'd rather avoid rod-ended LCAs if I could, as I don't want to increase more NVH unless I absolutely have to.

The GTA had stock stamped LCAs as well, and it didn't do this (that I can recall).

I can try stiff shock settings, but I was told when I was buying them that they can be set and forget (I was uncertain about a shock that had to be removed to be adjusted), and I made sure to put them at the recommended setting before install. Due to what's involved, I'd like to wait on that one just yet.

Just driving along it feels fine. It brakes well, and accelerates well, and in a steady state corner, once it takes a set, it's fine there too (feels/sounds like I'm on the outside edge of the front tires, but I still have stock springs and sways - plan to get Strano hollow sways). It's when you take a back-road corner at "speed" (general around 60, depending on corner, because it's a back road, but I've felt it as low as 45mph, and as high as 100mph), and you snap the car into the turn (because it's sharp and you can't slowly roll into it), that you feel the jiggle/wobble in the back like it's not quite firmly attached to the road.

Sam Strano

iTrader: (41)

Might I ask why you seem to have some a condemning attitude? You feel the rear is lazy compared to the front, correct? What did I tell you about rebound settings when we spoke on the phone (if indeed we did, I ask that those that buy Koni's from me call so we can talk about them). Remember the rule of thumb? More rebound makes that end react faster. Try more rebound in the back before you condemn things. Or you could soften the fronts a bit to better match the rears.

I don't want to come across as harsh, but you have to understand that from my perspective I somewhat feel like the time I took to explain these things might have gone in one ear and out the other. Further you could have called me about this.

Please just try some more rear shock. I think even one click @ 20% more rebound than full soft (considering you are running 50% or so on the front) will help you out.

DrkPhynx

Ya got me all wrong Sam. It was never my intention to insult, and I am certainly not condemning anyone, least of all you.

I follow your research and developments with keen interest. I love the Watts link and will likely be buying one, and as stated above, I do plan to get a set of your matched sways.

I merely name dropped as part of full disclosure, and to show that I didn't just come up with it on a whim, but got the info from a GOOD source. (I was trying to compliment as much as anything, not condemn)

Also, I love the shocks. They really woke the car up and I don't regret the purchase at all. Again, I was just trying to give as much information as absolutely possible to try to help track this down. If I had to start over with another T/A, I'd buy the same kit from you all over again.

Sorry if it came across the wrong way.

I'm just concerned about this feel/behavior. I was resistant to stiffening the rear because you had suggested this rate, but more to the point - because I felt this problem before my parts went on as well, which made me think it wasn't the shock settings, but made me worry it was something else altogether (which, combined with the fact that I wasn't planning on making any purchases right now, is why I didn't call, I thought this was more of a general issue and not something you should be expected to trouble shoot just because I bought parts a while back).

I'll give that a go this weekend though.

Some more info, just in case it might help (as it's apples and oranges, it might be useless though) - the truck is horribly underdamped. It has stiffer springs and a 1" lower ride height from the factory (vs the non-R/T Dakotas), and the result is it's less harsh on bump impact (which makes me think compression damping is rather weak), but it will then bounce a bit after, which makes me think that rebound is also quite weak.

Like I said, I don't know if that helps or not.

Sam Strano

iTrader: (41)

Fair enough.... I'm guessing that the car overall drives at least a little better than it did before, no? It didn't come across that way. But I see better where you are coming from.

I still think you need to up the rear, or down the fronts to be a little closer and see what that does for you. I'd say up in the back vs. down in the front since you clearly want the rear to be more crisp and not the front softer....

I appreciate the fact you didn't want to call if you weren't buying anything. But generally I take the stance that I need to support my customers as best I can. Now I can't spend an hour on the phone but I like to think folks buy from me because I can offer them technical support that maybe others don't or can't, especially when it comes to suspension and handling.

I'd agree with you assessment of the Dakota shocks lacking rebound. Don't agree they are necessarily lacking compression (they could be). I don't think less harsh is bad, in fact it's good as far as I'm concerned. Too little compression would result in a lack of control of the unsprung weight.

CranMaro99

iTrader: (10)

That's weird. My R/T handles like *** compared to my Z28 even when the suspension on the Z was stock. Now with Strano/Koni/Umi full suspension it's awesome. Maybe the heater hose mod is doing it?

JD_AMG

Torque down the LCA's and PHB (don't remember the right specs for the stock ones, should come up in a search though).
I would also try setting the rear tire pressure higher just to see if it helps any, like as high as 35psi and work down from there.
When I was on stock suspension and just Konis I never had this problem, and I had tried different rebound settings (2, 3, 4, 5 from full hard front, and full soft and one turn from full soft in the rear).
IMO the car felt the best on the street with what you currently have it set at(front: 4 turns from full hard, rear: full soft), but handled the best with the front set at 2 from full hard, and rears on 1 from full soft.
EDIT: * I did not use the lower perch on the front or the heater hose mod *