Tires: Tread wear, tire life, street legal

Question
How much tread wear is acceptable before tires need to be replaced? My tires have about 9/32 of tread left. My shop measured them during my last service call. Is mileage a better gauge of tire life?

Answer
Hi Rob,

When it gets down to 4/32nd then that is when it is recommended to replace them anything under that is not street legal and that is considered a hazard . Well the mileage is something some people view differ then others when they don't service the tires properly like they should like checking the air pressure at least once a month and balance and rotating every 6,000 miles.