The wheels now need to be pushed on, as shown in the following photos:
Follow these steps:
- First, note that they have two flattened sides in their axle hole, like the encoder wheel.
- Line the wheels up with the axles, taking into account the flat edges, and push them on.
- Sometimes, rotating the wheels until they push in helps. You should be able to push the wheel on, being sure to support the motor from the other side. After doing this, you may want to realign the encoder wheel with their slots.