murf257

I need your help, while driving my Z06 with brand new tires, Michelin SS Pilot non-run flats, I get a harmonic vibration in the car. It seems to always be there but worse at 76 mph and up.

It hard to describe but its doesn't affect the steering wheel so I believe its in the rear. Its not a constant vibration but is more rhythmic in the sensation.

I don't know how else to describe it.

I know it wasn't there before the new tires, lug nuts and locks. It certainly wasn't there before I dropped an intake valve.

Your thoughts?

Mordeth

Recheck all lugs. Ensure they are torqued to 100 lb-ft. Check pressure in all tires. Should be 30-32psi cold. Were the new tires road force balanced when mounted to the wheels? There could be run-out. Simply means either the tire and/or wheel is not "perfectly" round. What are the road force balance numbers for each wheel and tire? I always have them write it on each tire when I have them mounted. There are tires that come brand new from Michelin that are off. Anything over 20# I send back for a free replacement. There are also variations in sidewall stiffness throughout the tire that can cause an imbalance. Sometimes a roadforce balance can't even cure it, but it can generally correct for runout. All of these things can contribute to your harmonics being off. Have you had the car aligned?

Sometimes it is simply road noise and caused by the surface of the road interacting with the tire tread. Does it happen on all/any roads?

Other things can cause this (driveshaft, bent wheel etc), but I would start with the tires as they were the recent change. Check lugs, check pressure, check alignment and have them roadforce balanced. It will tell you if there is a problem and can possibly correct it.

tdeweese

I had the same problem with my car for almost a year before I change (3) things that helped the problem until I finally got it 100%. First check your rear inner tie rod for movement by jacking up the rear of the car and grabbing the tire at 3 and 9 o'clock should be no movement if so replace inner or out tie rod. My inner was loose and my car only has 8000 miles on it. Second get the printout of your tire balance must use road force balancing and be under 10lbs of runout on each tire. Look for a Hunter 9700 tire machine. Use website for Hunter and enter your zip code to find a tire store or GM dealer who has one. Last have a (4) wheel alignment done; all the parameters should be roughly in the middle of FE4 suspension range (for the street), important they are very even from left to right as well. Like I said I fought this for almost a year drove me crazy, hated the car for it and now love driving it again!! Just came back from a run up to 130mph and smooth....good luck

cv67

sounds like a bum tire of balance job.
It started right after you bought them correct?

murf257

Yes, right after the new tires