DC hub motor torque calculations, understanding specs

trix312

Hello

I'm confused by the specifications given for a Heinzmann DC brushed hub motor. It is giving me different values of torque/emf constants, armature resistances and inductances dependent on wheel size. I would think the torque constant does not depend on wheel size, but that this figure is inherent only to the motor. Why am I wrong? and how would I figure out how much current the motor is drawing for a certain torque and wheel size?

Here is the data sheet:
http://www.ebike.heinzmann.com/image..._DataSheet.pdf