[knightm3]

I've got 6,600 miles on the Focus. Two days ago, I rotated the tires myself [in the manner recommended by the manual]. I confirmed all of the lugnuts were secure when I lowered the car off the jack, yet ever since then I've noticed a _slight_ cyclic low-pitched vibration from the front. The steering wheel does not shake at all, even under braking, nor is handling affected in any noticeable manner. What could this be?

 

[scironzts]

since you can't feel it in your wheel, what most likely happened is that the "vibration" has always been there... just less noticeable since your FRONTS were just in the BACK. ya know? might just need a balance done. why you would need one so soon boggles my mind, but hey, ya never know.

 

[microtonal]

I had this happen on my zx2 and the tire was bad.
I think they put it on the balancing machine and it wouldn't balance.

You could always have the tire checked and see if it is balanced.

 

[knightm3]

I agree I shouldn't need a balance after only 6,600 miles. Very strange. I'll have it checked out though.

 

[focuzdSVT]

You could have had some chopping in the rear tires, if that's the case it should be ok after a few days driving. You could have thrown a weight from one of the rear wheels.