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We're coming up on the time of year when the roads freeze overnight and thaw for the day, and studded tires are irritatingly loud on bare pavement. Because of this I'm thinking of getting the studless, high friction tires (such as Continental's Top Contact Winter).
I would like to know: What sort of winter riding are such tires good for, and at what point should I switch to studded tires?
I am (or was, in the pre-pandemic world) a winter commuter in Canada. The studless winter tires are great for everything except actual ice and much more pleasant on bare pavement. If you need to actually ride on ice (rather than glide over an occasional small patch) you should really get studs.
My current commute requires riding in the road through a few major intersections and it is a common problem here that the heat from motors and exhaust causes packed snow in city intersections to ice up. Because of that I pretty much stick to studs these days even when overall conditions seem good, but I understand in Finland you are more likely to be able to get where you need to go using only bike paths than here.
Based on experience with studless tires for cars: These tires look like they're optimized bare asphalt and packed snow. On slick ice they may have better grip than normal bicycle tires but nowhere near studded tires. In soft snow they are likely to be more slippery than tires with knobby tread. I would consider them for conditions where roads are rarely icy or maybe if the temperature is consistently below zero and bike paths are well maintained.
They are only a good choice if you ride on roads and are fairly sure that you won’t encounter smooth ice.
Normal road bike tyres (e.g. Conti GP4000s) are surprisingly horrible in winter conditions. Even a thin layer of snow slush on tarmac can make riding dangerous and difficult. Much worse than just wet road. You’d think the tyre would just press through the slush and contact the tarmac but apparently it’s not that easy.
Soft MTB or cyclocross tyres at low pressure can work quite well on slush, snow, mud and so on. They are surprisingly decent on rough ice (e.g. iced over snow) or packed snow. I assume this also applies to winter bike tyres like the Conti Top Contact Winter. MTB and cyclocross tyres have an advantage when it comes to climbing out of ruts or riding in mud.
I feel like the main problem with any kind of stud-less tyre in winter is that in ≤0°C weather you can almost never be sure that there won’t be an unexpected patch of smooth ice somewhere.
I hate studded tyres because of their noise, rolling resistance and weight, but they are really the only solution if you need reliable grip throughout a ≤0°C winter. With studded tyres the only bad “surfaces” are deep or very wet snow (because you just “swim” in it and it creates a lot of resistance) or a thin layer of packed snow on roads. The layer of packed snow tends to crack and break apart as you ride over it, which can make riding quite difficult and dangerous. Low pressure MTB or cyclocross tyres tend to do somewhat better in this scenario.
I’d only consider stud-less winter tyres if you live in a climate which sees occasional snow but is not consistently enough below 0°C to really get ice.
Generally studless tires are best in situations where the roads do not have ice and the vehicle does not depend on friction for stability. For example bicycles depend on friction for stability but cars do not.
However, in practice you probably won't change your tires every day, so you have to estimate from the climate of the area whether studless or studded tires are better. For example, if the climate is such that there's a well-determined time when the winter starts, and the temperature during the winter is clearly far below 0 degrees Celsius and there's a well-determined time when the winter ends, you can expect that in the winter the roads are mostly free of ice and there's snow on the roads instead.
However, in climates where the temperature stays around zero for long periods of time, ice is very common.
I wouldn't use studless tires on a bicycle because the stability of the bicycle depends on friction.
Also consider this: on cars the usefulness of studless tires is based on the fact that many drivers choose studded tires. Thus, the drivers that chose studded tires make the ice rougher. So in areas that see lot of car traffic, the ice becomes soon very rough, thus friction with studless tires due to rough ice can be acceptable.
However, bicycle tires are very narrow, and there are very few bicyclists even during summer. In winter, bicycling falls approximately to zero. You are about the only bicyclist on the road if you choose to ride bike during the winter. Thus, because of the narrow tires and very few bicyclists, you can't rely on all areas of ice to become roughened from studded tire traffic.
Winter tires have a different rubber compound which provides greater traction once the temperature falls below 7 degrees. In cold climates, even if the air temperature is above this, the ground will often remain below this. There will provide better traction under 7 degrees than an all seasons compound which will become hard and lose traction when the ground freezes. They also have a deeper tread for displacing water and slush.
Studded tires are generally only suited to ice and soft snow. Outside of those two conditions the cost (noise, rolling resistance and price) outweighs any benefit.
If you had multiple wheelsets with studless and studded tires you would look to switch whenever there was snow or ice on the ground. You may get away with the odd day with patches of ice as long as you're alert.
I live in Nova Scotia, Canada and we have maybe 3 months when there is likely to be ice on the ground. It doesn't snow often, maybe once or twice a fortnight, but enough that if the snow isn't cleared ice will form and last until spring. I generally don't ride as much during this time so haven't been able to justify purchasing studded tires (and I don't own a fat bike).
If I'm riding during these times, and generally only to exercise the dog, I'm extra vigilant and stick to plowed roads where the ice is thin/ slushy or there is salt/ grit. I also never turn or brake on surfaces I suspect have ice.
