It seems to be common knowledge that the tires with more tread should go on the rear to avoid oversteer situations.
I just had to replace 2 rear tires due to a deformation and they do indeed have more tread than the front but from reviews I have read, although they have great snow performance they do not have great ice performance. They are Good Year Nordics and have 95% in snow but only 75% in ice.
My question is that although they have deeper tread, doesn't the ice performance mean that this may in fact lead to a situation where they have less grip than the front and an oversteer risk?

Secondly, the V70 has some ESC (electronic stability control) - as I understood it, if you get oversteer you should steer into the skid and also accelerate instead of brake! The ESC mentions that it will actually slow down the car or slow down one side of the wheels instead...

 

You would have to know what the ice rating on the front tires is as well as how much of the original tread has already been used in order to evaluate the scenario you propose. Personally I never mix tires if at all possible, especially in inclement weather, just because of this issue. I have driven cars with mixed tired in snow and ice and it can prove to upset the handling. As for the ESC, you are correct. And just as the automatic transmission mix rate has caused there to be a majority of drivers incapable of driving a manual trans, this technology will soon render roads filled with drivers unable to handle poor road conditions without the crutch of traction/stability control. I'm not saying the technology shouldn't be used. Just look at how many accidents ABS brakes have cut down, but as drivers rely more and more on this type of technology they will also be unable to drive without it. JMO

 

Unavoidable for me. I just had to for 4 new singer tires due to a nail puncture and age and now I only have cash fire 2 used rear winter replacements.

I guess my question on the ESC was that the manual says it shows the car whereas in an oversteer it should actually be speeding up the car by accelerating?

 

ESC will never speed the car up. It works to correct a skid by braking individual wheels as needed to correct the skid. Something a driver isn't capable of.

 

I've lived with snow my entire life and I've never had a problem with oversteer in the snow. Maybe I just drive cautiously. However, I have had problems with braking and steering which is why I fly in the face of convention and put the best tires up front.