Where can i find the wear bars...thats a good tip.
If you look around the tire sidewall, on the edges, near the tread, you'll normally find small arrows or dots or other indicators at various points around the sidewall, up near the edge of the tread.
(EDIT - I just checked the Pirelli on the rear of our 2011, and it has
TWI molded into the tire around the edges of the tread instead of a dot or arrow. Obviously that stands for "Tread Wear Indicator" as I could see the wear bar in the tread adjacent to each of the TWI marks.)
Those are wear bar locators.
Follow them across the tread, looking down into the tread valleys looking for a small portion of the valley which is raised, a little taller than the rest of the valley.
That is the wear bar.
The tire should be replaced by the time the tread wears to the point so that it is even with the bar.