so if 2mm (wear bar) is toast and new sticky tires seem to have around 6-7mm of intial tread depth what is a good guideline for semi used tires for an stt day, min tred depth reuquirement maybe
If you even think that they are too worn, replace them! The confidence gained by replacing tires is much cheaper than repairing/replacing bodywork, bone, leathers etc, because you went cheap on the tires.