I hate design of the wheels of my lawn mower, always loosen up and falls and don't have bearings ball so wheels moves like crazy: For that reasons I make this new wheels with ball bearing and self-locking nuts, no more crazy and lost wheels.

For this project i bought:

• 8x22x7 MM 608ZZ ball bearing (8 units)
• M8 self-locking nuts (8 units)
• M8 threaded rod

After printing, put ball bearing one on each side wheel with rubber mallet, screw the rod on position after cutting in apropiate lenght and fix with nuts. Take a look don't to tight, wheel may be spin freedom.

Uploaded stl, freecad file and photos, feel to free modificate for your needs.