Tarmo XTP121 Instruction Manual page 94

On tracked model, remove the hex nut and lightly
tap the shaft's end to dislodge the ball bearing
from the left-hand side of the frame. Be careful not
to damage the threads on the shaft.
Remove the other bearing from the right-hand side
of the frame by removing the snap ring.
Remove the other snap ring from the right-hand
side of the hex shaft.
Carefully position the hex shaft downward and to
the right before carefully sliding the friction wheel
assembly off the shaft.
5. Follow the previous steps in reverse order to
reassemble.
If you only want to replace the rubber ring,
proceed as follows: