I've been getting a consistent vibration at highway speeds since replacing my rear shocks. Nothing special, just KYB Excel-G's. After replacing, I thought I had damaged the right rear due to a bad install, so I bought another and replaced. At this point I'm on the second new right rear shock, and put my summer wheels on, and the vibration is consistent (so, not the shock, not the wheel).

I did lift the entire suspension with my jack during installation in order to relieve the pressure and properly align the lower shock mounting bolt. My guess is that something else that needs replacement got shifted during my work, and now needs replacement (maybe the bushing?). Curious if anyone else has had something similar.

 

Is the vibration consistent with speed or engine rpm?

 

Fixed it; likely culprit was a torn bushing on the upper right rear knuckle (the one at the bottom of the shock). I had already bought 2 replacement bushings; ended up having the stop perform the labor as they have a press. Here's a list of all the work I've performed since my last post, for brevity:

• Replace both rear upper knuckle bushings
• 4 New centering rings for my Enkei GT7's (two were cracked completely, one had a few missing teeth)
• Rotated all 4 rotors
• Replaced all 4 calipers/pads

Was still feeling a bit of vibration on the highway after the bushings were replaced, so maybe one of the other things was also contributing. Either way, rides like a dream now.

 

Thing is, vibration at highway speed isn't from a static bushing, it's from a rotating component. There's a good chance that whatever else they loosened/tightened is the actual culprit.

You could literally have every single bushing on the car 100% blown out and it will not cause a vibration at highway speed.

You said you "rotated" the rotors?

Have you had the tires road force balanced? If it's eating up your hubcentric rings it's probably something with the wheel/tire being out of balance.

Make sure you test the CV axles for ANY PLAY WHATSOEVER, that can also contribute to eating up the hubcentric rings and since the rears don't turn you will almost never hear that typical "clicking" sound from a CV axle failure on the rear.

 

The cracked hub-centric rings are likely the cause, even a miniscule amount of play between the hub and wheel bore face will cause vibrations at highway speed.

I rebuilt my entire front suspension including inner/outer tie rods. I was chasing a vibration at highway speed and noticed the vibration went away when I swapped to my winter tires (OEM rims). Checked the centering rings and sure enough the front ones had a slight amount of play and weren't perfectly snug between the hub and wheel. A $20 set of plastic rings fixed my issue.