Stingraynut

Going round sharp bends in my 88 Z52 suspension, if I hit a small bump, like a cat's eye, the rear stutters (or skitters) sideways 4, 5 or 6 times .

This is new.

I first noticed it the week I had to drive around with one rear shockabsorber missing. (had to send a new shock back under warranty)I assumed the skittering was because of the missing shocky but now that it's replaced, the problem is still there and very obvious.

The car feels a bit unsafe on bumpy corners at average speed. I'm guessing I damaged some part of the rear suspension while the shocky was off - or that could just be a co-incidence ?

I've been running 39.5psi in the rear tyres for a while to soften the ride on sharp bumps. I don't think that's the cause, this problem turned up suddenly.

The shockabsorbers are reconditioned Bilsteins and 8 weeks old.

I've had my vette for 20 months and this skittering sideways is a new thing. I'm hoping someone will recognise the problem and tell me it's the rear sway bar or the so and so.

S'nut

JAKE

Wow, 39.5 psi is a LOT of tire pressure. When I want a softer ride, I run 28.

Jake

lead foot 85 vet

sounds like your rear end is out of alinement..........go have it checked.

scorp508

The higher the tire pressure the easier it is for this to happen. I run ~35psi up front and 32.5psi in the back.

BIG JIM 54

Yeah,

If I run over 26 lbs. in my '87 Z52, it rides like a buckboard. I've had the "supposedly" harse-riding '84, and '85 Z51 and this Z52 is the hardest riding, feel-every-bump-in-the-road street car I've ever been in, even with new KYB's. It wouldn't be so bad if it handled as well as the stiff ride would suggest. But it doesn't.

I've got a set of "soft-ride" spring s now. Going to get them installed when I get the U-Joints replaced along with a new hub bearing.

BIG JIM

JAKE

Exactly.

Jake

SilverBeast

Me, too. 39 pounds will almost guarantee skitter if it's sideways and hits something.

vader86

Lower the rear tire pressure to about 35, and check the rear toe rod ends.

h rocks

If it's happening on a surface that's more "wave" like with a fair amount of suspension travel, you are experiencing bumpsteer. If your suspension components are in good conditon, that's not usually something that the average driver is going to sense. However, if your toe rods, or the bolts locating them above the diff are loose etc, or the actually ball studs/joints are worn, you can get enough toe change that it will definitely make your car very unstable. If you're experiencing the skittishness on harsh, washboard surfaces, I would agree that the high tire pressure is not your friend. In any case, if you have not had a recent 4 wheel alignment in a while, you may want to have it done. The cam bolts are notorious for slipping and causing rear suspension alignment settings to change.

jerkyboy

Like Hrocks says, check the toe rod attachment. My vette started doing that the other day. I was freaking out that I needed new bearings etc etc.. Got under the car and noticed that one of the bolts attaching the toe rods to the top of the diff was missing!!! $.35 and two new bolts later, no rear end movement - tight as a rock.

Stingraynut

Thanks Scorp, Vader and others - the tyre pressures probably are magnifying the fault. They were fine on good roads 4 weeks ago when I drove in our capital city of Brisbane but 1000 miles further North, where I live, the roads are bad.

The bumps in question, that caused the 'skittering' were things like 'cats eys' the reflective square bump on the centre line every 10 metres or so. Or delaminated road surface, not ripples in the road..

thanks everyone for info on what to check. I shall lower the tyre pressures tomorrow to 35 and see what changes, then jack the car up on the weekend and inspect the rear suspension . Any pointers on how to check the ends for movement ? Use a long screwdriver etc ?

Jake and Big Jim - here's one of the interesting things about vettes - if, like Jake, you have 16 inch rims, then I believe that the tyre pressure thing may work the other way, but on the 17" rims, more pressure seems to give me a softer ride - I've had advice from others here about that too.

I see Big Jim has the 17" rims on his 87 and is complaining that the ride is worse - of course it may be the shocks but I'm betteing the trouble started when the 17" rims went on ?

There's a lot of variables in each year, it makes it doubly hard to offer advice unless you have the same year or setup. 85-87 had much softer springs (Z52) than 88-91, plus 88 on had 17" rims = less rubber between the rim and the road.

Thanks again

S'nut

JAKE

Just like many other things, I tend not to get locked in on actual "numbers". I let the engine - or car ride/handling/tire wear in this case - tell me what it likes. I begin with the factory recommended setting, then try different adjustments and monitor the results.

Just play with the tire pressure and see which setting gives you the ride you're looking for. Then monitor tire wear to make sure the wear is even across the tread.

I'd start at 26 and move up in 2 psi increments. Once I noticed ride harshness I'd back off to the previous setting. Below 26 the sidewalls will probably start to wiggle on you which you can feel SOP. Same thing happens with drag slicks when the pressure is set too low.

At 32 psi, I noticed my center was wearing more than the outer areas so I realized 32 was too high for even tire wear. 28 seems to do the trick for me.

Just my thoughts.

Jake

REDC4CORVETTE

I think you need a front and rear alignment about $75.00
most shops and the rear end fluid is real bad that will cause bad problems with sliding,Look on your door the tire pressure should be on the sticker but 33 lbs for most vette,Just my experience.

95AquaC4

Does anyone think this could be a differential issue since he's run these tire pressures all along?

JAKE

Let's not over-engineer the solution to this problem.

All that's needed is a simple process of elimination here.

Drop the tire pressure about 10 psi, then drive the car over the same roadway where the car skittered before and see if it continues to do it. If not, it was the high pressure causing the problem. If it still does, then begin looking elsewhere.

Jake

vader86

Neh

Fozzy_Bear

Where did you get the soft ride springs?

ples454

Alignment. Mine did exactly the same thing. Scared me for a while...perfect now

PreferEuroRacing

When I first got my Vette last year I had the tires up to 38-40 pounds. I was bouncing around like crazy, even little bumps in a turn would send me two-three feet sideways. GM recommends 30 lbs. on my '94. I now keep it 28-32lbs. depending on what kind of driving, if I'm going to have a passenger, and if the roof is on or not. Try different pressures and see what works for you.

Stingraynut

OK, I like Jake's attitude, I'll drop the pressures - I've been experimenting with everything from 28 to 39 - I think 39 gave me a softer ride - I have really bad roads where I am. It will be a good test now to go back to 30 and see how it feels.

Thanks for all the replies and ideas. I'll post back if it still skitters and 30psi - and if it does I'll get the suspension checked out. BTW I changed my diff oil last year, drained completely and used GM additive as recommended.

I'm planning to replace the bushes in the suspension - I can get polyurethane ones but I'm worried they'll make the ride stiffer than it already is ?

S'nut