cgladish

I wonder if the GS's have the same suspension set-up as the Z06's?
( being wide bodied )
???

choppychop

There are differences in the base leaf spring rates and the GS. The GS is set up for bigger wheels and tires. Im not here to argue any point but to offer to the OP what took me hours of research and info gathering from racers and set up shops. Rotating mass changes spring rate.
I had problems when I went with a 12� wide wheel and a 345 tire that were resolved after changing to a ZO6 rear spring.
Whether or not thats his dilemma I do not know.
But something to consider.
Like its already been pointed out “ Physics are a bitch�

Revette

I once had a wobbling issue that you would feel at low speed. It turned out to be a broken belt in the tire. The tires that I experienced the problem with were new so it can happen at any time.

Jclgodale3

No. Factory 2017 z06 wheels and tires. 19 front. 20 rear. But you are right in that I️ am getting NO “active handling” messages on the DIC

BWF07

I am sorry, I got this one mixed up with another post on wheels and tires where that OP is want to run 20's on all four corners.

jaredtxrx

This could definitely be you issue. The TPMS and Active Handling system, and ABS are all tied in together.

Also, what size tires do you have on the new C7 wheels?

jaredtxrx

I would love to see some kind of documentation as to how rotating wheel mass affects spring rate. Because I'm not so sure you are correct.

cgladish

as I'm not a engineer of any kind, I'm just expressing my basic understanding of the situation. I did a quick google search and came across a couple of articles that, appeared to address this issue.
I've read over the years the issues people starting used 20" wheels.
unless you also upgraded the brake size, the added mass caused some extended braking distances. i know that braking isn't the issued discussed here. it would seem to be the shorter sidewall combined with the larger diameter tire, that, has a big part in this.
(as their is less side wall to offer an assistance in ride compliance. )


again, do not take my word, this is just my understanding.
please do your own research and compare the findings.

Garry in AZ

Not to get the post off topic, but extended braking distances due to large diameter wheels does occur all the time. However, the reason is not because of added mass, but because of the greater amount of leverage the larger diameter wheels apply to the caliper. Think of it as adding a pipe on to a breaker bar to more easily turn a stuck bolt. The larger wheel does the same thing to the braking system.

Garry

cgladish

I agree about the leverage application. but wouldn't that same leverage also have some effect the spring rate too?
I knew I should have taken some physics classes in high school.
I may be getting in the deep end for me.

Jclgodale3

Larger? Taller? Or wider? Or both?

cgladish

I do not any formal back ground on this, I'm just using my own common sense & experience.
in regards to the size, I would expect the diameter ( larger O.D. ) to have the biggest effect. a wider tire will add weight, and if / when, combined with a "larger" tire, I have to believe will have an effect on the suspension ( spring rate response ).


let me know if I'm off base.

Jclgodale3

Ok...here's the specs of the tires "old and new"
I went from the 18"/19" wheel combo (Factory GM 2007 z06 setup) to a 19"/20" wheel combo (Factory GM 2017 z06 setup)

Old front tires are 275/35/18 which are 25.6" tall
New front tires are 285/30/19 which are 25.7" tall
Old rear tires are 325/30/19 which are 26.7" tall
New rear tires are 335/25/20 which are 26.6" tall

Very very little difference in overall diameter of fronts or rears.

I haven't driven it over 35mph because the unusual hopping/lurching happens only under hard blipping of the throttle so wasn't comfortable getting it out on a main road. Backing out of the inclined driveway at an angle it almost feels like the rearend clutches are sticking/binding. But only with the new setup. Not with the old setup.

johnodrake

Do you have any friends that would let you swap out your rears with theirs to test? (C7Z, C6 ZR1, C6 427 Vert)

Jclgodale3

swap for the old size? Or an identical set of the 2017 size? I already swapped the rears back to the original 07z06 rears to test as posted above

Riverdog

I have done wheel/tire swaps/up-sizing in the past on some of my previous vehicles--but never on a Corvette--and have never had any issues other than the weight differences of larger wheels--I went from a 16" wheel/tire package to an 18" wheel/tire package--and by keeping the overall height of the wheel/tire close to the original--as the OP has listed above--I never had a any issues as the OP has described. From my experience, there should be no problem doing what the OP wants to do size-wise, but I'd be interested in learning how much of a weight difference there is between the base combo and up-sized combo. I almost flunked high school physics, so I know nothing about "rotating mass and its affect on spring rates," but I wouldn't think there'd be enough of a weight difference between the two sets of tires and wheels to throw the OP's car off so much.

MYCoupe

Well I can tell you that whatever is causing it is not because of difference in tire diameters. I did the exact same conversion on my GS as far as tire/wheel sizes without any issues.

Grimlock13

Only thing I can think of is that the 2017 vs 2006 wheels have a slightly different offset. As in a few mm, BUT because you said the wheel is hitting the brake duct. That may be the problem.

I would try a couple mm spacer on the rear wheels.

choppychop

It’s amazing how many people will reply without reading the entire post...

Unsubscribed

tloon

I have a set of '16 ZO6 take off wheels on my '10 GS. 19 and 20 with new Michelin's all around. Fit perfect, and ride exceptional.