I recently trued a set of rear drums from a Mexicano Beetle for a buddy who
could not find a local jobber equipped to do the work.  With less than 2 Kmi
on them, the drums had .010" and .013" runout on the ID.  The curious thing
is that the turned OD surfaces were almost right on the nuts with barely
.0005" (that is 5 tenths!) runout.  After they were trued, they were as
symmetrical as they would ever be considering the class of the job.  Here is
the rub: once the work was done, they required 20 g. and 25 g. of weight to
balance them.  As delivered with the eccentric OD's, there were no balance
spottings nor weights.

Now, were the brake shoe sweep surfaces originally cut off center as a way to
balance these things?  Looking at how accurately the raw casting was made, I
would have thought that once trued they would have required little, if any,
balancing.

By the way, the reason for the machine work was to cure a brake pulsation
during light braking.

Rich