Theduderino wrote on 01/01/22 at 08:43:19:Sounds like they let it go without adjusting the belt to the belt was constantly riding heavy on one side
Who's bike are you talking about?
The sad fact is that the original single row bearing in the pulley hub eventually becomes worn, and the result is that the belt tension pulls the rear pulley crooked in relation to the rear wheel. You really can't "adjust" the pulley to be straight without making your rear wheel crooked.
The test is to grab your rear pulley and see if you can wobble it (not rotate it) - if you have play and can wobble the pulley....then your rear bearing is worn and it should be replaced. Replacing it with a single row bearing will work for a while - but a double row bearing works much better!