It took about three hours of Googling to find out how to measure the runout
of a brake disc, so I'm sharing the info with the list for archival
purposes.
You have to mount the arm that holds the runout dial indicator to a piece
that moves along with the disc. This can be the castelated nut at the top of
the kingpin, the steering arm or the castelated nut of the stub axle.
Because I could get a pair of vice-grips on it with plenty of room, I chose
the steering arm. I made a three-joint jig to hold the dial indicator out
of aluminum bar stock. It was designed pretty much along the lines of a
human arm. It has to hold the dial indicator rigidly against the disc face,
but still be easily repositionable. I clamped this to the vice grips.
If I were going to be doing this regularly, I would have bought a
goose-neck dial-indicator holder that would clamp via vice-grips to the stub
axle nut. Much easier and more strightforward.
The dial indicator has to be very perpendicular to the disc face. It's
easier to manuver the arm if you haven't yet mounted the brake caliper. (I
had one on and one off.)
One disk read .001-inch runout, the other .003-inch runout. That's within
spec, but if I were going to be using the car daily, I would be temped to
remount the disc to the hub and see if I could improve it.
Say, do you guys ever actually work on your cars, or do you spend all your
time complaining about the weather and correcting each other?
Cheers,
Rick in MD
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