> down to 0C / 32 F (he didn't test colder conditions)
I get that people live in different places, but that's a huge caveat. How's that winter if you're not below 0°C? That sounds like "winter tires are worse than all-seasons tires in winter if you exclude winter".
It would only make sense to require them every winter if the large majority of winters were quite cold. As such, nowhere in the US requires winter tires, but someone else noted that Quebec does. This makes sense, since even a mild Quebec winter will spend most of the time getting below freezing.
I would be very surprised if there were a place that required winter tires by law where the winter does not always get and stay at or below freezing for significant periods of time almost every winter.
(But the winters are cold).
It's winter if it's noticeably cooler than summer. For instance London's climate has a January average minimum temperature of just under 3C, which is very clearly winter compared to the July minimum of 14C. (figures from Met office site on their Heathrow station.) While the temperature does drop below 0C sometimes, it is not consistently below zero.
In southern England pretty much nobody changes tyres for winter -- you just use the same set all year. Optimising for "2C in the wet" seems about right...
If it's not actively snowing for a few days roads get clear by thawing during day because of salt/cars being hot/sun shining.
The "summer tyres get too hard in the cold" idea could very well come from places where the typical winter is at least < -5°C. It's not uncommon in central/eastern/northern europe for temperatures to be < -10°C for extended periods of time.
winter tires, especially the snow versions, are straight out a source of danger here in central europe.
i just put some snow chains in for the winter surptises, and ride with my summer tires because its grip is clearly better on dry and wet bithumen, even in near zero temps, which is most of the season.
[edit] obviously this is a tradeoff--I'm trading slightly reduced hot/dry/wet performance for massively increased winter performance. The reduction in summer performance is small enough to not be noticeable, whereas the increase in winter performance is large. On all season tires I would have to chain up a dozen or so times per year, often just to move the car like 3 car lengths out of a parking spot. I've only ever had to put the chains on once with snow tires on the car, and that was bashing through 6" of unplowed crusty icy stuff up a steep driveway.
I've currently got something like 15k mi on the tires and 2.5yr of year round use. They appear to be wearing evenly and normally.
I assume we're both making approximately the same optimization but you're going for better snow & ice performance at the expense of some summer and wet stopping distance, and neither tradeoff seems obviously wrong depending on our driving situations.
Seasons are called summer, autumn, winter and spring and each last three months and that bears no relation to whether or not there's snow or sub-zero temperatures.
In the country I live in atm the rules regarding winter tires are not the absolute dumbest but they're still very dumb: you need to have either winter tires or all-seasons tires "if the conditions are winter'y". Which means, basically, both sub-zero AND either wet or icy. Sub-zero and all sunny means winter tires aren't mandatory. The reason it's still dumb it's that that correspond to, at most, 10 days per year. And this forces a lot of people to have worse performing tires during much more than 10 days. Which is probably the cause for a lot of accidents (e.g. people on days where it's + 3 C would be safer with summer tires, that do perform way better than "I've got winter tires because tomorrow at 7am it may or may not be -1 C and it may or may not be raining").
Not that's of course dumbtardation but there's worse: there are countries where from that month to that month of winter, no matter the temperature, you must have winter (or all-seasons) tires. And at times you'll have an entire winter without freezing temperatures.
So politicians who voted these laws are basically creating more accidents due to cars having inferior tires (the tires lobby does love it though).
It's sad but it's how it is.
The worst tires however are all-seasons.