I've read a lot of stuff on this topic using the search feature, but I have not found the answer to my dilemma. I can not get this car to feel stable at speeds over 50 mph. It was not a driving car when I purchased it.

Things I have replaced that would affect handling........
Rear spring with a TRW fiberglass
Trailing arm bushings
Strut rod bushings
4 new shocks
4 new tires
rebuilt the power steering cylinder

It is not an issue with the alignment. I have tried every combination in regards to camber and toe with both the front and the rear settings. I've went with neutral camber on all 4, tried slight negative on the front, with neutral in the rear, and then tried slight negative on the rear and neutral in the front. Right now it is set as slight negative camber on all 4, and toe in is about 1/8 inch in both front and back.

Nothing feels loose in the front end. I don't feel any slop in the steering wheel. The wheel bearings aren't bad. It seems that no matter what adjustments I make in regards to toe, or camber, the skating on ice sensation is never really affected. Maybe a better description of what the car feels like is that it has a pivot point in the center of the car. It feels like the rear end wants to come around the front. I have had other people drive the car while I followed. and the car tracks straight. I can be going 50 mph, and let go of the wheel, and it doesn't pull to either side. It's just when I turn the steering wheel a little left, or right, it wants to keep pulling either direction, and it's hard to get the car back under control going straight.

One last measurement I did tonight before throwing in the towel, was to check the caster. I ran a 2x4 across the front of the front tires, and another behind the rears, then measured the distance (left side vs right), with the tires properly inflated. I was off by just under a 1/2 in from side to side. Even at that, I still don't think that's my problem. I have probably made no less than 50 test runs in the last 2 months without solving the problem

Any advice would be much appreciated.

TIA....Dave

 

assuming all the front suspension is in good shape i would move to the rear end and look at the wheel bearings and the axle shafts. if the axle shafts are moving in and out it will give you a rear steer situation like you describe.

 

you need to be able to tell us what 'Not Stable' means.
Also what tires are you running?

Vettes are notorious for rut running AKA tram lining, wher the car darts around on roads that have ruts int he traffic lane.

try driving on a good cement 4 lane flat road. Tell us how that feels

 

If I understand your issue correctly, sounds like a power steering issue (and a potentially dangerous one, at that) rather than anything alignment related. I'd get that diagnosed and solved ASAP before it decides to just go full-lock one direction or the other at the most inopportune time. BTDT myself, and lucky I'm here to bring it up, tho by all accounts it's a rare occurance. FWIW, after the PoS pulled me across opposing traffic on a 4-lane and very nearly put me into a pole, I got out, cut the belt, went home, changed underwear and promptly converted mine to manual. Hope yours doesn't try to off you before you get it sorted.

 

When I have the rear on jack stands, the wheels feel stable when I try and wiggle them. Would a bad axle retainer be noticeable when trying to move the tire by hand while it's off the ground? I will investigate this further. Thanks for the ideas

 

I am guessing by your last paragraph that you are attempting to do your own alignments. What you describe checking is not caster by any stretch.

The way you describe the car it sounds like one of two things to me, a skating sensation almost always is the rear toe being off. It does not take much, maybe 3/16" or so.

The steering wheel not returning sounds to me like somebody adjusted your steering gearbox when it was not centered and got it to tight on center.

FYI I align cars for a living, it is my full time job. I align roughly 1500 cars yearly including many classic cars.

 

Tires are Cooper Cobra P255/60 R15

It's hard to describe the not stable feeling. When the car veers a little left or right, I have to keep working the wheel back and forth to get the car back straight, It's like it wants to go either left or right, but not straight. I wish I could describe it better. As long as the car is going straight, all is good. Another example would be if I hit a bump in the road, the car wants to pull either left or right, not stay straight.

My description almost makes it sound like there's some play in the steering box. That's kinda what it feels like, but I don't detect any freeplay when I turn the wheel when the car isn't moving.

 

Based on your last post, what's the condition of the rest of the front end? ...idler, steering box, tie-rods, *****, bushings...

 

You may very well be right. I'm doing my own alignments with strings, tape measures, levels, and straight edges. What I can't figure out is why after all the adjustments I've made, nothing seems to effect the skating sensation. I have run negative camber, positive camber, toe in, toe out, and nothing seems to affect the way the car skates. I will look into the steering box tomorrow, and will focus on the rear toe. I thank you for your input.

 

Nothing seems loose, or ready to fall apart as far as I can tell.... If I had a limitless budget, I would just replace everything, but I don't have that luxury

 

How is your steering control valve.....
I had a similar problem, when turning left or right there was a delay because the valve was worn and had play in it.
Just a thought,Good Luck.

 

I'll make this quick as I am going to bed but here is how I would set it. Run 1/32"-1/16" toe in front and rear. You do realize to set the rear toe you have to move the shims on the front of the trailing arms right? Moving the rear strut rods in and out only adjusts camber. I would set slight negative camber on the rear, maybe 1/2 degree in at the top.

If you sight down the inside of the rear tires they need to be the same distance left to right. Not one side further in than the other, you can also check this with a string along the outside of the rears and measure to a point on the frame near the front tires to ensure equal distances.

Set the front camber nearstraight up. Unsure of what the desired caster is but you definitely want positive meaning that the upper ball joint is behind the lower ball joint if you are looking from the side. Caster and camber on front is adjusted with the shims, these will also change the toe. Toe only is adjusted with the tie rods, you have to adjust this after setting caster and camber.

Good luck.

 

I don't think there is anything wrong with the steering control valve. The steering is responsive, and has no resistance.

 

I'm well aware of the shim adjustments on the trailing arms. I just bought new stainless shims last week I will adjust as you indicated. Thanks I will post back in the coming days as to whether this fixed things.

 

Based on your description of things that you have done and my 28 years with my 78 dialing out the handling quirks of the C3 I would say the following:

1. Steering-Something in the steering mechanism, most likely play in the steering box. I had mine blue printed/rebuilt. Also the steering valve possibly.
2. Upper and lower control arm bushings worn. I replaced all of mine with poly bushings which eliminated a ton of front end steering play and twitchiness.
3. Rear strut rods-I use adjustable competition strut rods with heim joints-no bushings-made the rear much more stable.
4. Tire pressures-don't run too much pressure. My car always felt twitchy with the the 255/60/15 tires of all brands until I switched to 255/45/17 ZR ultra high performance summer only tires!

Hope that helps!

 

Thanks for the suggestions jb I will replace the upper and lower control arm bushings. I run my tires at max pressure. I will experiment with lower pressure. That's one thing I hadn't considered.

Next chance I get, I will check the steering box. I read some of the Jim Shea advice on steering box adjustments so I will have an idea what I'm doing.

 

You may want to confirm your steering box. i found this while looking into making ajustments to the steering box:

In Car Adjustment Method
A third way is to make adjustments to the gear by feel in the car. The real concern when doing it by feel is that overtightening some of the adjustments can result in internal damage in the gear (which can be very expensive to fix.) Also, overtightening can result in sticky steering and poor to non-existent steering returnability. In other words, the steering wheel may not come back to the straight ahead position after making a turn and you will have to turn it back yourself. Obviously, adjusting a critical system such as steering and driving the car to confirm the settings must be done with great care!

 

Problem solved. It was slop in the steering box. I cant believe I didn't pickup on this. If nothing else, I've become pretty decent at setting camber and toe after having readjusted it umpteen times. It was really nice to take it for a ride without having a white knuckle grip on the wheel.

Thank you to all who have offered advice

 

Don't want to hijack this thread, but what equipment do you use? I worked for Hunter from 2000-2002, wrote a whole lot of alignment specs during those days. They certified me on both light and heavy vehicles as part of the job, by the end of my first alignment class I was one of two guys in the class the instructor was letting work on the execs' cars.

 

Glad to hear you got the problem fixed. Doesn't it feel great to know you figured it out and fixed it yourself, (of course with the help of the forum)!