Hard data on all-seasons vs winter tires [closed]

Question

The current popular consensus seems to be that you should switch to winter tires during the winter. In its radical form, this conviction is more like "winter tires are better than all season tires in the winter no matter what" but it also comes in many more gentle flavours. It also of course depends whether we are talking about safety or just the driving comfort.

Regardless of a particular wording and a particular aspect being discussed, I see only anecdotal evidence and common-sense reasoning - no hard evidence. Even here on SE (here, here or here) the answers contain only opinions or anecdotes and no really useful facts.

What I've found is only this ADAC test (I know that they've conducted this test before - IIRC results where very similar) where one of top-shelf winter tires Continental WinterContact TS 860 are compared to all season tires.

The result is in favor of these winter tires but:

1) it's a really small difference between them and some models of all season tires

2) they are even not the best tires for braking on the snow (!)

3) this is only a single test with a small subset of available tires

Are there any more objective comparisons between all season and winter tires? Or perhaps some other non-subjective arguments in favor of switching to winter tires?

To keep the question focused, let's narrow the discussion to subzero temperatures on snow and on plowed roads in temperate continental climate (i.e. northern Asia and United States, southern Canada, and northeastern Europe).

Answer 1

If you really want to have specific answers, you need to be a lot more specific about your questions. What are you trying to optimize for your situation? Are you in an environment with regular deep snow? Months of cold temperatures? Do you have the option of working from home if the weather is borderline? Do you have lots of freezing temperatures but rarely get snow?

It's easy to find real experimental data comparing specific vehicles using specific tires in a specific situation. For example, here's Tire Rack's test comparing summer, winter and all-season tires on an ice rink. My favorite data point from that test is the 10 mph stopping distance: the winter tires stopped almost 20 feet before the all-season tires. That's a compelling data point if you have to drive in traffic in icy conditions.

In the end, the winter tires are going to have a lower glass transition temperature than all-season or summer tires. They will also have different tread block design. Both of these will increase the available grip of those winters in their target environment. I chose to purchase winter tires for my car because, while we don't get months of deep snow where I live, we do get snow at very inconvenient times. I wanted at least one car to be reliable on unplowed and untreated roads.

Here's a practical example using the cars in my garage and the area where I live (some freezing temperatures, some precipitation, occasional deep snow). Both of these cars are AWD and have turbocharged 4-cylinder engines. They are different makes and models and one has all-season (hers) while the other has winter tires (mine). Obviously, this means that I can't do a detailed double-blinded experimental comparison (too many different variables). However, there are some coarse observations that I can make:

1. My car and my wife's car can both drive at all on plowed treated roads. We both have to be more careful on winter roads because we're not idiots and we have to allow time and space for people who are.
2. We can both stop in the snow at all. Braking distances are longer because snow. However, my car doesn't squirm under panic braking (i.e., full ABS).
3. I can stop my car on ice. Braking distances are significantly longer (surprise, lower friction on ice!) but it's much less of an "oh crap oh crap" feeling.
4. I can drive up a snowy hill. We live in an area with quite modest hills but they can still catch people off guard. There have been many trips to work where I've had to drive around someone in a FWD car who's sliding backwards down an inch or two of semi-packed snow on a hill that wouldn't cause me much effort on a bicycle in the summer. What tires do they have on their car? I couldn't tell, they were spinning too fast....

If you're trying to stage a test to illustrate how this set of tires makes different compromises and engineering choices than that set of tires, it's easy to do.

In the end, you have to decide how to spend your money.

Answer 2

The problem with winter tread vs. all-season tests is that most tests are very subjective. It depends the vehicle, road surface, and road conditions.

Most winter tires are heavily siped from the factory; sipes are cuts in tires for extra traction wikipedia. This greatly improves ice and snow traction, at the cost of dry and wet traction. So, this adds the additional cost of running all-season tires in the summer and winter tires in the winter.

My rule of thumb is to run winter tires if your live in a place the receives a lot of snow, have a car that has poor traction with standard tires, drive many winter miles, or live in a remote area with little maintenance.

With that said, I've driven thousands of miles with and without snow tires. They are worlds better in the snow, but they do not brake anywhere as good in the rain or dry pavement.