All-seasons tyres have been around for some years, but earlier interpretations focussed primarily on offering products that were little more than half and half combinations of conventional summer and winter tyres. They were reasonably effective, and provided the best available compromise then, but fell well short of the performance of good summer and winter tyres in the appropriate seasons. So the arrival of Michelin CrossClimate tyres in 2015 was a radical step forwards, for they were much closer to the performance of the best of winter and summer tyres. You might not choose them for performance motoring, but for most drivers they offer near to the best of both worlds over the four seasons. Other tyre manufacturers have responded by offering similar products with matching all-seasons performance. They all cost a little more than season-specific tyres, but much less than two sets of tyres for winter and summer, and far more convenient for those who really need good winter mobility, whist avoiding having two sets of wheels and tyres.
So what of the technology involved? There are significant changes in the properties of most tyres around 7 degrees Celsius, with a band between 5 and 10 degrees when neither summer nor winter tyres can be at their best. All-seasons tyres are designed to avoid the main compromises involved with summer and winter tyres. The tyre carcass, the rubber compounds used, and tread patterns, are all suitably modified, with minimal sacrifices in their outright performance in any weather. They cope better with wide variations in temperature and road surfaces, but with particular focus on traction and lateral grip in winter temperatures, and on ice and snow. That means in some areas they employ softer rubber compounds, like natural rubber, often mixed with fine ground silica, that don’t harden up in freezing temperatures, and also have very good wet grip. To this end, they have many ìsipesî, or fine, often zig-zag pattern slits, cut into the tread blocks, to help prevent slippage on wet tarmac, and in sludge, ice and snow. Synthetic rubbers offer better wear characteristics and are still used in some parts of the tyre, but all-seasons tyres tend to be more flexible than summer tyres, and therefore softer, and quieter, riding. Since winter often brings very wet roads, with low temperatures, tread patterns need to displace standing water well, with deep drainage channels to clear it fast and prevent aquaplaning, and they also need properties that prevent the treads becoming clogged with snow. Add to these the necessary qualities to offer reasonably good fuel economy, and it’s quite a challenge for the tyre designers to hit the right compromises.
Directional patterns are clearly evident in many all-season tyres, and asymmetric tread patterns for all-season driving may have seasonal objectives, with some tread areas dedicated for winter conditions and others to summer conditions, but all-seasons tyre tread designs vary considerably. Asymmetric features are absent from Goodyear Vector 4Seasons and Michelin CrossClimate all-seasons tyres, but are clearly evident in the more sporting oriented Goodyear Eagle Sport All-Season, and the highly rated Nokian WR G2 tyres. Possibly due to their Finnish origins, the latter are strongly biased towards winter use, and thus a good choice for those in snow-prone areas.
For those who own serious performance cars, normally fitted with summer tyres in larger diameters and widths, and often of low-profile design, availability of all-seasons tyres in such sizes is rather limited, with only a few 40 profile all-seasons tyres available. This highlights the compromises of extreme tyre and wheel size options and suggests that a more practical and safer alternative in winter is a set of smaller and narrower wheels, fitted with all-seasons or full winter tyres. It should be noted, however, that all-seasons tyres are not available in run-flat designs, which means that full winter tyres, preferably on narrower rims, are the only alternative to summer tyres.