Front suspension trouble?

[tomtom72]

When ya have a problem, ya always come home for help!

I'm not sure I have a developing front end problem because this is the first C4I've ever driven. 90/ZR-1, 15.6K miles on odo. This is what it's doing:

Over closely spaced waves in the road in turns & at certain vehicle speeds, not potholes or broken pavement, the car gets very "upset". The front seems to loose feeling and the front seems to vibrate or osclliate & I can feel it in the chassis and the steering wheel. It's almost like the chassis is twisting diagonally from one front corner to the opposite rear corner. It also transmits an occlitation thru the steering wheel that you can feel. This seems to be happening in corners where the front tire that is "unloaded" does this dance like the shock can't stop the "unloaded" spring osclliations. I'm not talking about really pushing the car thru twisties like a better car handler than I could do. I'm talking moderately exceeding a posted limit for a given curve, not racing speeds. Speed that you would think were well within the envelope for a vette. On smooth road it gives the "glued down" feeling. This wierdness doesn't happen all the time, rather it seems there is a unique set of circumstances needed to produce it. I should add that my ignorance of front transverse leaf spring suspension is not helping me.

Things I've done so far to trouble shoot this:
I keep the shocks wipped weekly to check for excessive oil leakage...None or not much to even make the road dirt smear much when wipped with a dry rag.

I tried pulling on the top and bottom of the front tires and I can't get any movement or clunking from the ball joints. The joints were over greased and the bags came out so I think I'll have them done before spring because lubbing them with the bags poped is a PIA!

The wish bone bushings are not cracked or pushed out & the shim bolts are tight. The shock bolts and the sway bar end links and sway bar mounts are tight and the bushings are not cracked or pushed out.

The rack mount is tight & bushings good and the "tie-rod" ends don't seem to have excessive play but I did not discon them to see for sure. They don't seem to move when you pull on the bottom of the tire. I know I should separate them to be sure, right?

The rotors are not warpped, no pulsing in the pedel, and I have meat left on the OE pads...only 15.6K on the odo. Oh, slowing buy rolling out of the gas or even draging the brake makes this "feeling" go away very quickly.

I'm gonna get the front tires re-balanced to eliminate a very slight balancing error...only seems to be at a specific speed & I have to concentrate to feel it in the wheel. I didn't wack a curb or drive into a crater to bend a wheel.

Sorry this is so long. I wanted to be as complete with the info as I'm able to be. Thanks for any light thrown my way!

Tom oh no lights on the DIC & no service ride control light.

[Aurora40]

That might be normal. The unloaded tire won't have much weight to help damp the ocillation, and so it might more easily get jiggling over wavey pavement. Does the car seem to skip over or get hairy? Or is it more just annoying?

The C4 is definitely not a luxury platform. It shakes and ocillates pretty easily, at least the ones I've owned do. But I've never had it upset the handling, it's just annoying. It is a 15 year old car, and even for 1990 they were a bit rough.

It might be letting off the gas or applying brake helps because it puts weight back on the wheel? Don't you have new tires, though? I'd think they ought to be balanced fairly well still.

As an aside, I'm fairly sure my rotors and pads are all stock too (23k). I wonder if it's ok to keep using them or if it's better to replace them? Do pads get "old"? I do try to bed/break them in every now and then with a few medium speed stops, I am of the opinion this is a good practice to do now and then, not just when the parts are new.

[Corvette95]

stock wheels,wheel size, any special tire? Allignment can cause wandering, also "grooves" in the road will cause the large tires to try to follow the grooves if you have never driven a Corvette before?

[tomtom72]

Hey thanks guys! Sorry I forgot the wheel/tires are stock size for a Z. It's been 25 yrs between vettes. The first was a 72 LT-1 w/F41 suspension and it's been too long for me to remember much except to say bump steer from the rear T-spring!

Okay kidding aside...I remember the one & only time I drove this C4 w/out the roof....and this twisting feels kind of the same, except w/out the roof it's much more pronounced. I suspected that because the outside wheel in a turn unloads, the waves on some of our roads up here were giving me the "oscillation" I'm feeling. I just was not sure as I have no previous driving impressions on a car with front T-spring...so I just didn't know. I have been stuck with DD's since 1985 so a vette is new to me all over again. Bob, I think that I only "think" the car's grip gets upset & it makes me slow down...it is more my own lack of knowledge or familairity with the car than a mechanical problem...at least that's what I think. On the brakes...I try not to be too abrupt in their use, ever. I guess I don't have much faith in the 15 yr old stuff either! That's on the list but truth be told to me they seem to work just fine...even at 15 yrs old.

Thank you Bama & Bob for your time!

Tom