Some estimated calculation for the "Planet Rider" motor:

Max rpm at 48V = 1000 48/17 = 2820 rpm
Motor Torque at 20A = 0.17 X20 = 3.4 NM

Frequency of 3-phase supply at 2800rpm = 2820/60 X12/2 = 282 Hz
26" wheel rotates 322 rpm at 40 km/h
Hence the reduction gear ratio = 2820 /322 = 8.75 : 1
Wheel Torque at 20A = 3.4 X8.75 = 29.8 NM

Comments:
1) This motor seems to be of good design and have high torque.
2) With a gear ratio of 8-10 for 26", it will be a very good motor for 26" wheel.
3) Theorectically a direct-drive motor (at 322 rpm) will be about 8 times the size.
4) The attached geared hub motor has similar winding/poles arrangement with a gear ratio of 4.