when do you need new tires??

Tires should be replaced when the tread is almost gone.

Most tires these days come with wear bars on them. Tires are supposed to be replaced when the treads wear down to the wear bars. Wear bars are little bumps of rubber between the treads.

Here is another explanation - 2/32 of an inch and a way to measure tread with a penny

http://tires.michelin-us.com/care/buy_when.html

Thank you!!!

Not driving much, I go by the depth of the weathering cracks on the sidewalls. When a quick look elicts an "ohmagawd!' it's time.

when they are flat

I agree with Roger. I just had my tires replaced because of the weathering cracks.

You only get your tires replaced when you see weathering cracks? Wow, that seems pretty dangerous to me!

As far as I've ever been told, weathering cracks are often indicative of other problems- like advanced dry-rot of the tire.

Certainly the "penny test" and looking at the wear bumps would be a safer way to make your determination.

Having a properly adjusted suspension and geometry, in addition to rotating your tires at regularly scheduled intervals- will ensure that your tire last for a quite some time...

No, no, no, the tread was still fine, but there were weathering cracks...

Go by whichever occurs first, southerngentleman. To do otherwise seems pretty dangerous to me. You might have noticed that I mentioned that I don't drive lots of miles. Weathering from sunlight and pollution are continual - tread wear usually doesn't occur till the car is moving.