[Shotimes] Vibration or picky...again

[cmichaelo@optonline.net]

In my case the wheels are brand new and so are the tires (Pilot Sport).  I totally trust the shop  that mounted and balanced the wheels.  Also, when I put the front wheels on the rear, there are no vibrations at all (slicers up front.)

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.

On the first two sets of wheels, however, I was always able to cancel out the vibration by rotating or swapping the front wheels.  So I never dug into figuring out what the problem really was.

Since no wheel is perfect and always has some radial or lateral runout, I think I simply had the vibration whenever the small runout in the wheel "added" up with the runout in the hub/rotor/whatever.

Conversely, when I then rotated/swapped the front wheels and the small runout in the wheel "subtracted" from the runout in the hub/rotor/whatever, I experienced no vibration.

The current set of wheels probably have less runout, and thus I feel the effect of the runout in the hub/rotor/whatever no matter how I mount the wheels.

This weekend I'll do some more measurements on the lateral runout of the rotor, which I have not looked at yet.  

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?)

As it is right now, where I feel vibration in the steering wheel only at 70mph when driving on the road, there is no vibration to be felt when spinning the wheel in the garage.  Radially everything looks good.  Laterally, there is a slight but clearly visible wobble in both rim and tire.  I'll measure this weekend.

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???).


Michael
94MTX,green,BOS+,Koni/Intrax,Baer,Corbeau
SHO items for sale: http://hometown.aol.com/cmichaelo/for_sale.html