TxRedC6

Hey guys, I just purchased my 2008 C6 last Wednesday. Everything was good up until Monday when I actually started getting on it, Got on it 1st and 2nd are nice and smooth just until I start throwing in 3rd at around 90ish, it starts to sway from left to right really bad so I have no choice but let off. The car is fine if I feather it through the gears but only starts to death wobble at WOT. I'm not exactly sure what the problem is, I'm taking it Saturday to get it checked out at the dealership but I'm not sure they'll be able to pin point the problem. I've looked through some threads to try and see if other people had the same problem and what solutions they did to solve it but people say different things, like rear alignment(rear toe), change shocks, bushings, tie rods, sway bar, etc... Until I read that some people fixed it by changing their tires, looks like everyone who has encountered this problem was with Michelin Pilot sports or super sports and that's what I have on the car. They are 295-30-19s. So please can someone help me out here guys? Anyone ran across this problem, if so what was your solution? Thanks in advance. Car is a manual, with 23,000 miles

timd38

I have Michelin Super Sports with a 416" strocker, coilovers and Quaife with 3:73 gears and no wobble at 120+. The 120+ plus was on a track, not the local school zone.

TxRedC6

Nice bro, I bet she moves. The pulls I do are on a isolated road beside some old train tracks, its rare to see a car come down that road.

timd38

Can you swap tires with someone?

TxRedC6

I'm working on that, I'm going to a friends tire shop this weekend to see if he has any. If he ends up not having any then I might just buy a used set of different tires to see if that solves the problem.

TxRedC6

I'm going to take a look at my local Craigslist.

old motorhead

What pressure are you running in your rear tires? I had this trouble at extremely low (16 to 18psi) tire pressures at the drag strip. Happened right after the 3-4 shift. Aired them up to upper 20's. Still there, but not as bad. Went home, got it aligned perfectly and it was still there.

After a little research, here and elsewhere, it's apparent, to me at least, that the Michelin PSS's don't like anything less than mid 30's for tire pressure. After airing mine up to this range, I've had no trouble at speeds up to 140. Hope yours is that simple. BTW: I'm using 345/19 rears along with 285/18 fronts on a 650rwhp Grand Sport.

Boomer111

I wonder if this is due to the soft tire compound.

I know from experience that when new rubber was put on the Peterbilt (meaning the 8 drive tires) it took a few thousand mile for the truck to stop squirming over the road. Now this was at much less speed and more predominate in the turns. Still it was discomforting to have the feeling that the truck wanted to roll over.

I am guessing the tires need to harden a bit with wear or as suggested they just require a higher psi.. I could be way off base here but it is what comes to mind.

TxRedC6

Left tire pressure is 32 PSI and right it 31 PSI. I'm going to play with the pressure tomorrow after work and hopefully it helps a bit. Might be forced to buy a used set of Pirelli's this weekend to see if the tires are the problem.

TxRedC6

I'm not sure what the problem is, hopefully it is just the tire pressure or tires because this problem is driving me butts. When I got the car I was like yes finally I get my first corvette after trading in my 13 GT 5.0 but then this problem came up . Hopefully I didn't get a lemon

tarik916

Thanks for the tip! I had the same issue with my PSS's at the track after dropping the pressure to 26. My active handling kicked in from 2-3 shift until the end of the track and the rear was dipping left and right.

haljensen

Are you sure of the size? 295/30/19 is undersized for a stock '08. What size front tire? A mismatch between front and rear sizes can cause A/H or T/C problems that will be magnified by speed.

Boomer111

Might be on to something here..

TxRedC6

You have a great point. Front are 265 35 18, rear are 295 30 19 and the car came with the tires

Wakemaker89

Could it have something to do with the road? Have you noticed the wobble anywhere else or only at this location?

meanjoe

This problem is almost always either alignment or tires. Shocks, air pressure are not the cause. Keep us posted.............. But I'll take that back and say that under certain circumstances shocks, if really blown out may contribute to this issue.

old motorhead

Airing mine up to 35psi fixed it for me. This is on a 2013 Vette with less than 5K miles, fresh alignment, and almost new Michelin PSS tires. It's fairly easy and cheap to add a little air and make sure that's not the issue.

mikeCsix

OP, if your car is a base model, the rear tires are too large. They should be 285's. The other issue may be both rear alignment and tire pressure. I run Michelin PSS's on my GS and have had no problems with them including several hpde's. They like higher pressures than the 30/30 on the door, mine seem to like 35/32 though the tire installer said Michelin recommended 37/35. I found 37 to be too much, they heat up enough to get to 42 and the DIC starts an over pressure warning.

old motorhead

While those tires are wider, they're more than a half inch shorter than the stockers. As far as the Vette's brain is concerned, width doesn't matter. Height (revolutions per mile) does. A shorter rear tire running with a stock size front tire can fool the PCM into thinking there's rear tire slip going on. Traction control can put a halt to the party. Not sure what it does to active handling.

meanjoe

If jacking up the air pressure that much higher than it's supposed to be fixes this then you must have other problems you don't know about. If at 35 PSI cold you'd be 40 PSI plus hot and that's not even safe. The tire manufacturers recommend a max cold pressure at max load because the same tire can be used on several different cars, so the car maker will always suggest the tire pressure. That's why it's on the inside of the door on every car made.