That’s a good question, and nearly impossible to answer completely without putting up a huge Excel spreadsheet comparing ambient temperatures, roadway conditions, tread design, and tire composition.

The Brickyard Rat provides the right answer (albeit somewhat simplistic but the concept is correct).
Modern tires depend upon different compositions to achieve best adherence to roadways with various conditions (dry, wet, frozen, etc.). Of course tread design is important (and that is a different discussion), but it’s the tire’s composition that really makes the difference in various temperatures.

If the roadway is dry (but not frozen); your summer performance tires heat while driving, and you can expect adequate to exceptional adherence. If the roadway is frozen (32F or Zero Centigrade); friction drops off significantly, the summer/performance tire does not heat (because of reduced friction on a frozen surface), and performance tires lose traction and become dangerous.

So why do snow tires work so well in cold weather? It’s the composition of the material used in the snow tire. The “rubber” remains soft and pliable even at sub-zero temperatures. The composition is important driving and stopping on ice, and the tread design is important driving/gripping in loose snow.

Drilling this down to a simple answer… If you can brake and stop well with your summer performance tires, you are OK. If you brake and notice some sliding when you don’t expect this, it’s time to switch to snow tires.

--Spike

 

+1

 

I am going to disagree (I think). I race autocross with summer tires. With each consecutive heat, the tires get warmer. When the surface temperature is 40 degrees or less, performance is poor. Doesn't matter if it is heat #1, #2, #3 or #4.

Just my observation of course.

 

My comments are based upon the tires I currently have on my car (my “performance” tires are Eagle F1 GS-D3… Fronts 245/40-18" and Rears 245/45-18"), and they seem to run very well all the way down to freezing (32 F). Once the ambient temperature hits freezing, they don’t work at all (and are slippery and dangerous). Frostbite Falls hit freezing here a few days ago, and I installed my snow tires… pronto.

The OEM Bridgestones Potenza RE040 (I ran before mounting the Goodyears) did not provide this level of operation. I suspect that this is due in part to the stiff sidewalls and “rubber” composition on the OEM Bridgestones. The Eagles performed very well until the temperatures hit freezing and the tires were unable to “heat” via roadway “friction.”

I should point out that I am reporting my personal experience, which is very limited. Readers of this thread should be aware that you have much more experience with the Z, tires, and driving than I do.

--Spike

 

Spike, you calling me a "simpleton"? LOL!

 

I drove year round with summer tires when I lived in south carolina but I don't want to try it up here. The one time I did try to drive on ice down there was to work and I was sideways most of the way.

Now I have some good all season tires and I'm not too concerned about it as long as I don't go out and act like an idiot.

 

Never a “simpleton,” but in fact, a wise person.

I need to develop your skill of answering/posting in 35 words or less. I get a lot of “heat,” criticizing my long messages/posts.


--Spike

 

I used to have Nitto 555s and they started losing traction in the 60s LOL
They are piece of sh*t tires