The main measurement we need to identify the correct axle is centre-centre (A),
along with the measurement to the mating surfaces; it can also be useful to
measure the diameter between the bolts on the brake drum.
These are measured
like this:
A = Attachment measurement (centre-centre). This is the measurement defined for axles on the Valeryd web site.
B = Measurement to the mating surfaces.
C = Diameter between the bolt hole centres on the brake drum.