There are typically 3 pairs of sealed bearings in a treadmill. There are a pair in each end of the drive roller, typically found in the front of the treadmill and a pair in each end of the idler roller, typically found at the rear of the treadmill.
Because these are sealed bearings they cannot be greased as a regular maintenance service routine.
When these go bad they typically make a grinding noise. The sound often vibrates through the entire frame of the treadmill often making it difficult to determine which roller has the bad bearing.
I often need to use a mechanic’s stethoscope to determine the source. Sometimes I need to remove both of the rollers for locate the bad bearing. Once found the best solution is to replace the roller. The cost and benefit of a new replacement roller is the most cost effective solution due to the material and labor cost of locating after market bearings of the correct size and replacing the bearings that are typically a pressed fit into the roller.
The third set of sealed bearings is found in the drive motor of the treadmill. When these bearings go bad they typically make a completely different sound that is unmistakable. (listen to the audio file below) As with the roller bearings, the labor cost and difficulty in replacing these bearings makes replacement of these sealed bearings unfeasible. In this case the drive motor will need to be replaced.
