cole3

I have a 2005 base.
it has a cam swap, 4.10 RPMTransmissions differential, longtubes, and a vararam intake. and probably some upgraded clutch. I have done no mods - there may be some I have yet to find lol

Anyways, I've had the car for a year and a half or so with no issues up until a few months ago where the car acquired a left to right sway from what feels like the rear when going high speeds.
The wobble is noticeable when going 130+, sometimes when changing lanes, and also around 70 sometimes if you really lay into it.
I've shaken down all four wheels and all four bearing seem to be fine, Rear shocks are maybe 6-8 months old, front shocks felt fine. I've also had all four wheels balanced and the car has been aligned probably 6 or 7 times because Oklahoma isn't known for perfect roads and it gets slightly off pretty frequently.
Ball joints looked fine, tie rod end links look fine.
Sway bar end links don't look like their in the best of shape, but seem to be functioning fine.
I'm out of ideas! I need more things to check! I also have an apt with the dealer on Tuesday so I can get their opinion for hopefully not an arm and a leg.
Any ideas???? Thanks!

mikeCsix

I'd check the wheel run-out with a dial indicator.

ColtaBilly

I'm no expert and wouldn't go 130+ (cheez), but could it be one of the tires breaking down inside?

Boomer111

Are you running OEM rims?

lathrash

Do you have locking lug nuts? I had a set on my car when I bought it and they created a vibration at high speed due to the locking lug nut weighing slightly more than the others. I replaced all the lugs with new ones and my problem went away.

cole3

wheel run-out??

Meh! Why have a car more than capable of those speeds and not take advantage of it?!
But the tires are roughly 6-9months old I'd say. Michelin super sports all the way around.

They're Z06 replica. Stock size.

I do have one locking nut on each wheel. I've not thought about that, but I'll have to give it a try. I also have a friend with a base c5 and I was going to switch wheels with him and run it to try and eliminate the issue being caused by a wheel.

Boomer111

Ok i had an issue with aftermarket rims. LG World Challenge rims to be exact.

The bore was 1mm larger than the cars hub. Long story short a wrap of tape around the hub solved the problem, as crazy as it sounds. Spigot rings can be used but the rim would of had to be machined to allow for one to fit. 3mm is the smallest spigot ring. The tech told me that sometimes the tape trick works.

I experienced vibration in the rear at 70+ mph. Never did the 130 thing,lol.

Hum centric or not this is my experience. BTW we balanced the rims a couple of time etc. to no avail. This was at a high end wheel store that deals with high end cars mostly. Hunter force machine at all that.

Something about the rims bore not resting on the hub creating a vibration. Even with proper lug tightening nothing helped until the tape.

BTW I got rid of the rims shortly after and went back to oem.

cole3

I wouldn't suspect that'd be in because it ran fine up until a few months ago. I should know if that's the issue when I swap on my buddies c5 wheels.
Also heard that if the car was lowered and one side higher/lower than the other that could be it so I checked and sure enough there was about a 1/4" difference, so I got those square and took it for a run and the issue still persists.

AORoads

May I suggest using the search and then advanced search function in the above red band. I thought I'd seen Mich. SS having issues with sway. Not sure if this is yours, but here's a recent thread on it.

https://www.corvetteforum.com/forums...eleration.html

Also, as to wheel runout mentioned above by mike, here:

http://www.tirerack.com/tires/tirete...jsp?techid=17&

As a check, I'd have someone look at the halfshafts, sway bar end links (at 10 years old, could need replacing), and go over every bolt in the rear to spec torque.

Boomer111

The car comes from the factory riding lower on the passenger side then the drivers. Something about when the driver seats it will equal out.

Many have posted the floor to center of wheel well fender lip for their measurement.

Usually it is within 1/8"-3/8" difference, side to side.

GM has an procedure for proper leveling of the car, and it is not the method I described above. You need a specific tool using the suspension geometry. And the car will favor the passenger in ride height.

You want to keep the forward rake angle too, something like 1 1/4 to 1 1/2 inches. The back being higher than the front.

Boomer111

The car comes from the factory riding lower on the passenger side then the drivers. Something about when the driver seats it will equal out.

Many have posted the floor to center of wheel well fender lip for their measurement.

Usually it is within 1/8"-3/8" difference, side to side.

GM has an procedure for proper leveling of the car, and it is not the method I described above. You need a specific tool using the suspension geometry. And the car will favor the passenger in ride height.

You want to keep the forward rake angle too, something like 1 1/4 to 1 1/2 inches. The back being higher than the front.

AORoads makes some good points, although behind my experience. Bill has a wealth of knowledge.

ErnieN85

ok here is your problem Michelin SS and too low pressure. pump up the rears a bit. they need 28 min when cold! after they are warm the pressure goes up and they will work. (it is sidewall flex)
I had the same problem and cured it

Kenny94945

If the issue just occurred after 1.5 years....

No one mentioned....check motor and transmission mounts.

Bent rim is suspect. Lost a weight weight. Else re-tighten all the suspension and cradles bolts you can get a torque wrench on. Inspect suspension bushings and shocks.

Best wishes and good hunting.

sliderbkt

I have a wide rear setup with 325 Michelin PSS. I had the same problem. I had it aligned, changed shocks, checked sway bar, upped tire pressure, and nothing worked. I finally played with the rear toe until I got it to go away. On My car I had to set the rear end dead square. I set it myself using a long board with a screw in it to measure off of the rim. I'm sure all tires are sensitive to toe. But, I believe the PSS are more sensitive for whatever reason.

cole3

Well, I've narrowed it down to something about the back wheels.
Swapped wheels with my buddy's c5 and went for a few runs.
first run was with both of his wheels and got to 161 with absolutely no issues. drove like a DREAM!
second run, I swapped my fronts back on with his rears still. Got to 145ish - also no issues.
third run just to verify with similar conditions, had all 4 of my wheels back on and low and behold at 107 I got the wobble.
Now let's keep in mind, these runs took place on a closed course and nothing illegal happened.

Next step is to take it to hibdons on Thursday probably and see if a wheel just needs to be balanced or if I have a slightly bent rim. I'm leaning towards bent rim because my LR tire has a very slow leak when I fill it to 30psi until it gets to 26 psi.

Thanks for all of the great ideas! This has been quite the task to track down the cause!

mikeCsix

Measuring run-out with a dial indicator will tell you if the wheels are true or not. The other clue is in your first statements regarding numerous wheel alignments needed from all of the pot-holed filled roads in your area.
Did you check the backs of the wheels to make sure they are clean, no rust/debris and the wheel hubs are clean?
Sounds like you are getting close to a solution.

mikeCsix

Also, my Michelin PSS's feel fine at any speed running a slight negative camber on the rear. If there is an issue with the tire, it's indigenous to the tire, not the brand or model. Michelin recommends higher inflation pressures than what we are used to with run flats, I've run them high and low and it doesn't seem to make a difference as far as stability goes, stickiness is another subject.

old motorhead

I'm running PSS's in the 345/285 size combo. I'm getting the same wobble. WAY worse at low inflation pressures. I aired my rears down to 20psi for some qtr mile work. It actually hooked 650 rwhp pretty damn well. The trouble started right after the 3-4 shift. I aired them up to 26 psi. They didn't hook near as well. The wobble was less pronounced, but was still there at about the same speed. I'm running Pfadt's "performance street" alignment specs. http://pfadtracing.com/pdfs/Corvette...09.12.2011.pdf Maybe I need to realign the rear end?

I was also concerned that maybe having the mag ride in the tour mode might have made the wobble worse.

sliderbkt

mikeC6- I think there is an issue with the PSS. Not necessarily a problem, but an issue. I think due to the tread design it is very sensitive to Toe. Camber does not seem to be a problem, just Toe. My guess is that due to the tread design it compresses the bushings if there is too much toe. It may not be a problem with the tire itself, but the tire may highlight something else. I think it is a great tire. But, the wobble can be frustrating.

Cole- It might be worth crawling under the rear and adjusting the Toe. You can count the flats on the tierods and put it back where it was if it does not help.

racerxrick

I am starting to catalog this issue and saving links to threads...THIS IS NOT JUST A CORVETTE ISSUE! I have found threads on GT500 and even BMW forums with just a little research. Michelin was kind enough to swap my rears out for $96 (sarcasm implied) and I still have the issue.

I posted the following to another thread today:

I have been following threads like this on multiple forums (it's not just a Corvette problem) and the issue is ALWAYS the same and ALWAYS related to Michelin tires! 100% of the time after reading through a typical thread eventually it comes out the owner with the "wobble" has Michelin's. To be clear not all owners with Michelins experience this.

Me: (702whp 2010 GS) I have been fighting this and I have two other sets of rims (drag pack and DR's on spare 19" rears)...with these other rears there is NO WOBBLE! Switch back to the Michelin PSS and under hard 3rd and 4th accel the rear end wobbles and it is VERY scary!

Michelin "exchanged" my rears and denied ever hearing of this problem (despite others reporting the issue and a friend reporting the issue directly to a race engineer at COTA). And yes I have another friend locally with his 675whp GS experiencing the EXACT same issue on his low mileage car.

BTW, I was charged $96 to exchange the rears for another set.

What really sucks is I love the wet/dry traction (lateral and straight line) but cannot trust these at high speeds as under accel the car "at times" will wag it's tail like a dog with a bone!!!!!!!!!!!

Going back to Discount this week to work on exchanging for another brand.