I used to run 10 PSI in the rear tire on my chopper to save my back too. That was a tube type tire though not sure I would want to run it that soft on tubeless but 28 should be OK. I never noticed anything different as far as the way it wore either. The soft front may adversely effect your handling though and given the wobble factor others have found you may want to rethink the pressure in the front.

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