Doesn't really matter which orientation a motor is set except with this one caveat. Some motors are not sealed and in certain orientations you could get more dust/debris in the bearing or motor which would shorten its life.
One good thing almost all motor bearings are inexpensive and easy to change.
Below, is the general codes for bearings. Bear in mind you can get a sealed bearing with a metal seal , a rubber seal or a combo-metal rubber seal.
Bearing Callouts:
- K - Cage with roller elements
- L - Removable bearing ring
- R - Ring with roller set
- S - Roll body of stainless steel
- W - Stainless steel deep groove ball bearing
Code:
(6)902 - This first number relates to the bearing type, typically most bicycle bearings will be a “6” which is a “Deep Groove”. Occasionally you will find a “7” bearing which is a “Single Row Angular Contact”
6
(9)02 - This second number relates the bearing series, which reflects the robustness of the bearing. As you go up the scale below from 9 to 4 the inner and outer race thickness will usually increase along with the ball size, this will be to help cope with extra load. Hope this helps..........
- 9 - Very thin section
- 0 - Extra light
- 1 - Extra light thrust
- 2 - Light
- 3 - Medium
- 4 - Heavy
69
(02) - The 3rd and 4th digits of the bearing number relate to the bore size of the bearing, numbers 00 to 03 have a designated bore size depending on the number.
- 00 - 10mm
- 01 - 12mm
- 02 - 15mm
- 03 - 17mm
Important Trivia : Numbers over 03 simply have a bore size which is 5 times that of the 3rd and 4th digit.
Suffix:
- 2 RS - Bearing with rubber seal on both sides. RS provides a better seal but more rolling friction than 2Z.
- RS - Bearing with rubber seal on one side, one side open.
- 2 Z / ZZ- Bearing with a metal seal on both sides.
- Z - Bearing with a metal seal on one side, one side open.
- E - Reinforced Design
- P2 - Highest precision
- K - Bearing with taper bore