Tires: Open shoulder/closed shoulder

Question
Our son is in graduate school in New Hampshire and drives extensively in winter weather as he spends all his free time skiing. It is time to replace the tires on his 2011 Subaru Forester and his limited budget means he is looking for all-season tires. A local tire salesman has convinced him he should buy tires that are partially open-shoulder and partially closed-shoulder. Our son says the physics of that advice make sense, but it is Greek to us --we were simply looking at tire reviews and Consumer Reports tests. Do you have any thoughts, given this particular situation, on the open-shoulder, closed-shoulder or open-shoulder + closed-shoulder debate?  We feel safety is the most important factor in deciding on new tires but don't know which of those options is safest. Do you have any other advice as we look for new tires?  We're just the parents, so your expert advice would be extremely helpful!  Thank you!

Answer
Rebecca,

First, if you take a look at winter tires, what you should notice is not whether the tread pattern is open shoulder or closed shoulder, but the fact that there are lots of edges - sipes = blade like voids that provide a paddlewheel effect, thereby enhancing traction.  That, much much more then the shoulder design, is what an all season tire with good snow traction should have.

Second, your son is old enough that he should feel responsible for his actions - and if he makes a mistake, he is willing to live with it.  While it is nice to have a mom that cares about him, it is also nice for an adult to make and live with their own decisions - and this one has relatively mild consequences, so it will be a good learning experience if he gets it wrong.