WHAT THE??? New wheels
 

Weird problem. Put 17 model z06 wheels and tires on my 05 Widebody. Had 06 z06 wheels and tires on it. 18/19's. These are 19/20's. No clearance issues except a very slight rub on left rear brake duct. Drove car once mounting and under light excelleration, rear end kind of hops/jumps unusually. Reacts almost like a rear wheel is loose. Back in garage, check torque on lugs...no problem. 100 ft lbs on each and the wheels are seated on the hubs properly. Spin the wheels with the car in the air and no wobble or warped wheel. Tires are Pilot Super Sport ZP's.
Drop it and drive it again, same thing. Any idea what the heck is going on? Going to put the old z06 rears back on today to see if it goes away but had no reaction like this before changing them out.
Open to suggestions to check

I have heard the old adage that wheels can make or break the car.

I am less than happy with my current 2011 stock polished five spoke C6 wheels.

I'm just afraid of running into figment or performance issues like the ones described by the OP.

Where did you get the wheels and tires from? Are they off a new C7 Z06 or are the aftermarket?

OEM 1900 mile 2017 z06

OP... have you changed shocks or rear leaf spring yet?
When I did my wide body conversion I put Z06 shocks front and back. AND swapped out rear leaf spring for a used Z06 unit.

Thats ALOT more rotating mass on your base set up...you have changed the spring rate by doing so.
I went thru all this your going thru now...
Choppy
:cheers:

the widebody conversion has been done for years.
This issue was not happening before putting on this set of wheels and tires with stock 06 z06 wheels and tires. Only started with the new wheel/tire combo

I have had the wheels checked my a wheel and tire company? They could be out of round or bent just enough that you cannot see it, but on the car under a load that is different. Just a thought. I don't think the mass is an issue seeing you were running the C6 Z06 wheels which are just little difference in size to the new ones.

Yeah, that is a good suggestion just to rule that the wheels are not bent or something along those lines. I swapped out my stock GS 18/19 wheels for Cup wheels 19/20 (same size as C7 Z06 ones) and have experience no issues.

Bad balancing? bad tire? Bad wheel ? Those are my guesses.

They were just mounted and “road force” balanced by a GM dealer 2 days ago. I’m sure they would have noticed a warped wheel or bad tire while mounting and or balancing...no?

Also, new gm TPMS’ installed. Just not married to the computer yet but I’m sure has nothing to do with it

I guess you have not had a lot of experience with dealerships. There is definitely something wrong and I expect it to be a bad tire or wheel. If you put the original wheels you had back on and thee was no issue, I think that tells you there is an issue with a wheel or tire or combination of both with the new wheels.
Final a top tire and wheel shop and take them their. Explain you issues and let then check the wheels and tires.

Mounted the older 19" z06 wheels and tires back on the car last night. Drove it and seemed back to normal. (no hopping etc) Has to be something in one or both of the rear wheels or tires. damn confusing

Could this be a Traction Control/Active Handling issue with the tire choice and wheel change?

I'm betting on the TC/AH thing. I don't know but maybe a tuner could change the settings

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?

shorter sidewall tire.
+ possible bent or mis balanced tire.

tire fitment
 

my money's with choppy-chop. people also run into braking issues, when going to a larger tire size. I don't think that people realize how much added mass & weight is added, even going up one tire size
(not wheel size ). this is a case of "cause & effect". going back to the original set-up works, because that is what it was designed for.
how often have you experienced a wheel or tire ( in this case 2 each ) being that far off. not everything today is a plug & play.


could be wrong, but physics are a bitch!


good luck regardless!

I had no such issues when I upgraded the wheels on my GS. I went from the stock 18/19 combo to the 19/20 combo using ZR1 sized tires and no issues at all.

He is running 20's on all four corners, so the AH.TC sounds alike it could be a cause, but I would think he would get the message in the DIC.