Dial Indicator
$25 up (depending on quality and source)
Industrial supply co, maybe pawnshop

There are shade tree ways to get a pretty good czech though.
You could take off the wheel, and with a big block close to the disk,
hold a pencil point against the disk and turn it. If you feel the
surface leave the pencil point it is probably out at least a couple
thou.

Be sure the wheel bearings are tight when you do this.
--
George Downs, The "original" Walrus3, Bartlesville, Oklahoma