[Shotimes] Vibration or picky...again

[Leigh Smith]

Well;
This is getting tough. Good thing I like brain-teasers!
OK - Belts can shift in a tire, for many reasons, sometimes just due to
curing /heat issues. Many symptoms. Tread could move laterally 1/2 in or
more, or it could get a bubble in the tread or sidewall, or it just may have
a "stiff" spot during rotation. (Old BFG tire employee / chemist / racer).
But your car vibrates with 3 different sets, so I'd rule all that out.
Same with 3 sets of rims - rule that out.
Now we are down to rotor / hub issues.
I'm betting your problem is in there some-where.
It's not bearings, different symptoms.
I have no experience with Baer brakes. Are the calipers solidly mounted? or
do they float on pins?
You mentioned a slight scrape during rotation - this usually happens with
even minor variations in rotor thickness. However, yours doesn't vibrate on
the brakes, so I'd rule out any major issue..
You mentioned hub/rotor runout. I'd measure the hub VERY carefully, with
machinists type tools, dial indicator, solidly mounted, etc. Runout should
be almost zero.
If you have solid mounted calipers, I don't see how hub or rotor runout
could be bad, 'cause the brakes would vibrate like mad.
But if they float, like stock ones, it will tolerate being "out" a little
bit.
My best guess would be a slightly tweaked / bent hub 'cause of that pothole
you mentioned. If it bent a rim, that was a pretty big shot.
If that part is OK, then it must be the rotors. Not warped but maybe the
balance is off. I'd have the rotors re-finished, and find a place that can
dynamically balance them..
George's on-car balance method, or the on-car machines that people used to
use, would correct for that as well, but if you ever removed / rotated
tires, you would have to have it re-done.
You could put the tire back on the same wheel if you kept track of how it
was "indexed", ie: which stud/hole.
Sorry this was so long, but it is a tough one.
Good luck!
Lee