Originally Posted by Kev
Put it on when the temp is cosistently lower than 4 degree celcius. At 4c or below, your PS2 will harden and you will lose your grip.
Yep, that's what it boils down to really. Snow is just the serious case. Stopping distances with PS2s are significantly reduced at freezing temps. I normally give up on the summer tires or summer car at the end of October or early November. Last year, October was plenty warm. We'll see what happens this year. I am selling some inexpensive 18" winter rims with TPMS here if anyone's looking and interested in a local pickup: http://www.m3post.com/forums/showthread.php?t=312446