You got it. I'll defer to the other guys regarding alignment & wheels.

Here's what I would never recommend doing. I would never lift the rear end on jack stands and idle the engine with it in gear.

Then I would definitely recommend against watching and feeling for wobble and uneven wear in the wheels/tires.

Don't do that.

I would always start with this. Or even rotate front to back, see if the vibration moves to the steering wheel.
Just because it was balanced, doesn't mean it was balanced, if you follow.

Because with disc brakes there is usually some amount of friction between rotor and pad whether you are braking or not. You might not feel it at lower speeds, or unless you are actually braking, but at 80+ mph it might be felt.

This is probably not the cause of vibration, but if you rule out everything else, it's worth considering.

Without inspecting the vehicle or knowing more details, it's gonna be tough to figure this out, so I'm just throwing out ideas that haven't been mentioned yet.


EDIT: Your hubcentric rings could also be the cause. Are they plastic or metal? You said you track your car, it's usually not advised to track a car with plastic hubcentric rings. They expand and can melt with the heat so this alone could be the cause of the issue. Hell, even metal rings can have this problem. They can expand/contrast/warp/etc etc. It's worth removing them and making sure you center your wheel correctly with the lug nuts and then seeing if the vibration is gone.

As long as your using the correct lug nuts, you really don't need the rings.

They are aluminum. If I try the stock wheels and it goes away, I’ll add this to the list of things to check.

Definitely have never done that. I’ll make sure to avoid that. That would be terrible if I accidentally do it.

I beg to differ.

I'm not here to argue with you, but there are lots of people all over the internet who back up my claims.


We'll start with our own forum:

http://www.ft86club.com/forums/showthread.php?t=23877

and now we'll move onto others;

https://grassrootsmotorsports.com/fo...y/13593/page1/

https://grassrootsmotorsports.com/fo...m/85470/page1/

http://www.m3forum.net/m3forum/showthread.php?t=336496


a guy in this thread had the rings fuse to his wheels:

https://forums.nasioc.com/forums/sho....php?t=1522131




Now, i'm not trying to say you shouldn't run them. That's totally your choice. But they are really only used to center the wheel on the hub when you tighten your lug nuts. Most aftermarket wheels are lugcentric, so as long as your using the correct lug nuts and you installed the wheel correctly, you shouldn't have any issues.



We are trying to diagnose a vibration issue, so I suggested something that other people have had issues with in the past.


I don't have any on my car, and it drives smooth as butter at 100+ mph.


So you can beg to differ all you want, but nobody else suggested it so I did. It's easy enough to check and see if the rings are causing the problem.


He tracks his car so his metal rings could of very well fused to his wheels, and might be creating a small amount of friction with the wheel/hub that is only noticeable at higher speeds.


OP: Please keep us updated! I'm curious to what is actually causing the vibration.

They're not fused to the wheels. Last time I rotated my tires, they fell out. Obviously, I put them back in.

Weekend synopsis.

Definition;
Original condition: Aftermarket wheels in the orientation that was causing the original vibration.



Action 1: Jacked up car and made sure aftermarket wheels were seated properly. No abnormal wobble was observed when wheels were rotated.

Action 2: Put stock wheels back on. Drove it up to 85mph. Smooth as butter.

Action 3: Put aftermarket wheels on except put back wheels on front and front wheels on back. If the rear wheels were out of balance, the vibration would migrate to the steering wheel. Vibration was much less than original condition, almost entirely gone. There was still a decent amount of vibration above 90mph.

Action 4: Rotated wheels again, back to original condition. Vibration was the same as after Action 3. Vibration did not migrate, wasn't as bad as original condition, and decent vibration above 90mph.

Hypothesis: I don't think its the wheels, given the above conditions. Would the wider wheels and tires amplify an issue with alignment? Since the stock wheels showed no vibration, maybe the alignment isn't that bad but with the wider wheels and tires maybe I'm able to observe it better?

Any other thoughts? Might try different hub rings.

I run MPSS on 17x9 with the same problem. Alignment is spot on but unlike you I haven't had my wheels balanced.

Is there play in your hood? My hood moves a bit and I'm thinking that may be contributing to it but not sure.

No play in my hood

Sounds like the vibration follows the vehicle speed and not the engine speed...?
If so, your engine should be fine. Everything after the engine (clutch, transmission, drive shaft, etc..) could be the reason. Seems like some imbalance somewhere is coincident with the resonance. Since the OEM wheels are smooth as butter, maybe it's your aftermarket wheels/tires/spacers.
Anyway, unless the aftermarket parts are from a top tier OEM supplier with high Quality Control standards, ALWAYS stick with OEM.

Wheels are Gramlights, tires are Michelin PSS, hubcentric rings are Muteki. Muteki is the only brand I don't know. Gramlights aren't an OEM supplier but definitely a top tier manufacturer. This also has started recently and haven't smacked the wheels at all to throw them out of shape.

Who mounted & balanced the wheels? You may have already done this, but have you tried a different shop for re-balancing? I know for one that the Belle Tires near us doesn't do very high speeds