[Shotimes] Vibration or picky...again

[Leigh Smith]

Michael:
..
3 Sets of wheels = not it
Q: Tires ? same set? or different ones?
Max Lateral tire runout spec (Ford) = 0.080 in. (1/16 in) (shoot for half)
Max Lateral Wheel runout spec = 0.080 in.(ditto)
Max Lateral rotor runout spec = 0.003 in
Max Lateral hub face runout spec = 0.002 in.
..
If the tires were always the same, I would check carefully for a shifted
belt in the tire, which seems likely since you said it goes away when you
put them on the back. These are pretty common.
..
Otherwise, Based on the specs and what you said, I'd check for hub or rotor
issues. Warped rotors are very common, but a vibration in a staight line
during cruise? That doesn't sound like a warped rotor symptom. A bent hub
could cause all the above.....but has the car ever hit a curb? Does the
rotor physically seat properly on the hub? I have heard of some issues with
certain rotors, but don't you have Baer?
..
Good luck & let us know what you find. See below
Leigh

> I've had the vibration problem up front for over 3 years now with 3
different sets of wheels.  It basically started, around the time that I
changed rotors up front.
>
> Wrt the radial runout of but the hub centerbore and the rotor, it is less
than 0.015".  The rotor though has to be mounted carefully to achieve this.
If I do it sloppyly, the radial runout can be as high as 0.025" (which is
probably still acceptable, no?)
>
NO - that sounds too high - see above
 >
>  Radially everything looks good.  Laterally, there is a slight but clearly
visible wobble in both rim and tire.  I'll measure this weekend.
>
Anything more than 1/16 in could mean a shifted belt - but only if the wheel
is straight - I recently had one with 3/8 in wobble & a mean vibration - but
if your rim is wobbling also could mean a bent rim, or deeper problem
>
> Another thing that tells me that the wobble is most likely in the
hub/rotor is that when spinning the wheel slowly by hand, the rotor scrapes
against the brake pad a certain spot on every revolution. Sometimes, though,
 it's only on every second revolution (go figure???).
This may mean a rotor width variation, which should also be measured -
and/or rotor resurfaced - but I don't see how that would cause a vibration