Yes, its just the tires. When I first test drove a C7 I had to maneuver the car out of a parking spot at the dealer. It clunked and jumped so bad I almost refused to drive the car for fear of damaging it. Glad I drove it. I was hooked.

Some of the forum members can be rude. Sorry

Enjoy the car, try and enjoy the forum.

 

keep us informed as to the root cause.

 

It could be what all C7 owners experience but worse with Z51, GS and Z06 (because of tire construction.) When it's below 40/45F when backing out of my side garage in the morning to turn down my driveway it's very bad so I don't turn as sharp and make a "K" turn. It does feel like the front end is falling apart if I don't and has in my 4th winter! In the Spring, Summer and Fall (and many Winter days in Eastern SC) I make full lock turns and no chatter or hopping, as GM calls the issue! At first I thought it was in the rear like the posi clutch issue I experienced in my Street Rod where I have to make the same full lock turn.

If that is the issue you are experiencing, just for information, this is what the cause is NOT:
1) Sticky wide tires (they are less sticky when cold and GM states in worse in wet weather, which I have validated.)
2) Lack if Ackerman steering compensation for the different front tire turning radius in a tight turn! Forum posters note it goes away when installing the same size winter tires! (That is with the same Ackerman compensation geometry.)

What is it? The high performance, low slip angles of the race car type Michelins! This is a picture/text PDF I made from my research after my first very cold day in 2013 that provides the technical details: http://netwelding.com/Wheel_Chatter.pdf

It's certainly possible it is something else as it was with my Street Rod where I called Currie who assembled my narrowed Ford 9 inch rear and they recommended changing the dif lub and installing the posi additive they recommended. That solved it with the Street Rod. However with a GS (and my Z51) you have eLSD that operates the clutches with a 3000 psi hydraulic pump and the computer.

 

Since I got my September 2013 built Z51 early there was little info re how bad the chatter or hopping as GM called it was! Yep the Owner's Manual had the classic note, "It's Normal," but that did not prepare, at least Z51 owners, for what happened. There was no tag at that time on the shiftier saying what you'll encounter and still frankly nothing published by GM to say why! Since I had the same width tires on my Z51, C6 and never experienced anything like that I investigated what the issue could be. I realize some roll their eyes at my technical explanations but it's good to know it's NOT a design defect!

I recall one post by a fellow who took his wife to dinner and when leaving on a cold night and he backed out of the parking slot and it "bounced" so bad he got out to see what broke. His wife wanted him to leave it parked and call the dealer in the morning!

For 3+ years I have jokingly said "Do not use full lock with a friend in the C7 when it's cold or they will surly tell all your friends what a piece of junk you bought!" There was a recent post where the owner's freind with a Porsche did just that and said he'd never buy a Corvette!

I just think of the great lateral acceleration I achieve when the tires are warm as I make "K" turns in the Winter!

 

And it's than, not then....
http://writingexplained.org/then-vs-than-difference

 

. ditto....and has been discussed often.

Unless you feel it a normal driving speeds, you GS is OK.

 

Yeah, I haven't heard a thumping sound backing up from the garage without turning. When turning it jolts the front tires, but definitely not thumping from the rear. Interesting it doesn't do it all the time. Some people have noted low diff fluid, but I don't think that makes thumping.

 

Been a couple of reports of a loud noise but would not call these "thumping."

One I get if I try to back-up without releasing the parking brake. It is supposed to disengage by itself. Mine doesn't. The times that it did release it was with a big bang! I gave up trying 3 years ago, I release manually!

The other is if the car is put away after washing without first driving a short distance the to dry off the rotors. Then brake pads stick to the slightly rusted rotors. It's actually not the pad sticking, it's a thin layer of rust on the rotors that causes a large bang noise as the pads break loose.

 

Yes not as much handling in the summer but I have no noises and I can drive my car after September with much better grip than the summer tires only.

 

Can anyone quantify the degradation in handling? I'm considering the new A/S tires for my 16 z-51.