how much minimum thread should winter tires have to get a decent traction in winter, especially canadian winters?

 

Tirerack recommends 6/32", but then again they sell tires for a living. I would say at 4/32" you might want to replace them. At 2/32" (legal limit) your snow traction would be slim to none.

 

Trust me. Do not wait till your treads are down to 2/32 because you will have hard time driving up a small hill. I didn't have snow tires but I did have all season tires.

 

I guess somewhere between 4/32 and 6/32 the tires are pretty much useless, and worthless.

I am also trying to derive a fair value on used winter tires. 6/32 is about 80% wear, 20 % life left. A used winter with 6/32 left, priced at $100 new, would be worth $15-$20, right? A used tire with 8/32, $50?