I had been driving my 07 GT all last week and did not touch it over the weekend. The only thing I did was re-torque all of the lugnuts and install the McGard locking lugs. I had removed these when I took the car to the dealership for body work. The car drove smoothly all last week after it came back from the shop.

This morning, it was about 45-48F and I noticed that for the first 5-6 miles of commuting, I felt a lot of vibration through the steering. The car tracked straight at 55 MPH, but the steering wheel would vibrate left/right rapidly.

It can't be ice on the wheels, and I'm pretty sure the McGard lugs wouldn't throw off the balance of the wheel since they are at the hub - plus these lugs worked fine for nearly 4 years.

After the tires got some heat into them, the vibrations seemed to go away because I didn't feel anything on the freeway at 70-75 MPH.

Was it because the tires had some flat spots from sitting over the weekend in the cooler weather? I checked the pressure a week ago and the tires were fine. These are the original Pirelli P-Zero Nero M+S with under 12k miles (looks almost new, the treadwear is not noticeable).

 

Check you tire pressure when the tire is cold

 

No doubt this right here. The fact the vibration went away after some driving chances are they had some flats spots. funny how some people will get them and some don't even with the same tire. If you had an out of round tire or an imbalance it may clear at a certian speed but would come back again. tracking wouldn't cause ( or shouldn't) vibration but tire wear.

 

That's what I thought, but it's odd that it'd develop flat spots over the weekend, since I've never had this issue before. I've had the same tires for almost 6 years and they've generally been very smooth. I'll keep an eye on them.

 

My Pirellis would do this as well. Sit too long cold overnight, get out, feels like it's out of balance... drive it a bit... heat them up... all gone.

 

I measured the mass of the McGard at 69 grams, while the stock lugnuts (17" wheels) were at 58 grams. I looked at how I installed them, and I had them near the valve stems. After a quick run around the company parking lot, I saw that many new Fords use the Gorilla lugnuts directly opposite of the valve stem.

I measured the McGards on my Cobalt SS at 73 grams, while the stock lugnuts were 41 grams!!! The stock wheels are 18" to clear the massive 4-piston Brembos on the front. The weird part is I don't recall a lot of vibration from the steering wheel, but I usually drive the SS when the weather is warm.

I'll keep an eye on the vibration on the GT, now that I have all stock lugnuts to rule out the possibility of the heavier McGard lugs.

 

Lugnuts aren't far enough from the hub to be a huge deal. It's the distance from the hub coupled with the weight differences that cause the vibrations. Which is why a paltry 1/4 ounce of weight in just the right place can make such a huge difference.

In the same radiant of the wheel at the same speed, but 1/2 the distance in, you'd have to put on a whole ounce to make the difference that 1/4 oz does at the rim. Or something like that, it's not exact, that ounce. it's actually somewhat logrithmic or perhaps exponential. It's not linear, for sure. It may be two. I dunno, it's maths, and I don't like doing it. It's Centrifugal force, and it's larger the farther out you go, so less weight is needed to achieve balance.

Conversely, a few grams of weight difference at the lug nuts distance from the hub is just negligible. If it were a couple or so ounces, maybe, but not 50 grams.

So the difference in lug nuts is likely not causing the issue. Not sayin' it's impossible, but... it's really not enough distance to make a difference. Not unless you're running 180MPH or something.