What 'abec' number spec are the bearings that are used in the balancer?

ABEC specs are relevant only for "High Speed " use. They are irrevelent in this application. Our bearings have standard specs, and the dual action of the bearing on the shoulder bolts give it excellent sensitivity. Better than 1/16 of an ounce accuracy. Statically speaking, with the weight of a wheel and tire, That is supurb. We balance AMA Pro Race wheels with them at National races. The balancer was designed to be a rugged, reliable, portable balancer that does not require to be level and should not fail in a "Dirty" environment.