09-11-2018, 11:54 AM
For what it's worth, there ain't no such thing as 'perfectly round'. A brake drum produced by modern mass-production methods might have a tolerance of 0.5 thou or so for roundness and 1 thou for concentricity with the axis. But it would also be substantially stiffer than an A7 drum and clamping up to something much flatter than a 90 year old hub. New drums are very good, not perfect!