Posted: October 22, 2012 at 12:54 pm by Pilvi
Thanks to aggressive tread patterns and soft rubber compounds winter tires (tyres) provide superior traction on icy or snowy conditions compared to all-season or summer tires. This applies both to acceleration, braking and cornering. The downside is that on dry pavement winter tires perform poorer than all-seasons or summer tires. Notably though the performance advantage that winter tires give on icy and snowy roads is substantially better than corresponding drop in performance on dry roads. In short, if you live in northern wintry climates, and absolutely can only afford one kind of tires, you might be better of buying only winter rubber.
The difference in performance can be huge. Recent Automobile article for example reports braking distances of 74ft (winter tires) vs 135ft (all-season) vs 332ft (summer tires) on packed snow from 30MPH. That is ca 350% poorer performance for summer tires compared to winter tires on packed snow. On the other hand, on dry roads, summer tires stop the car 30% better than winter tires.
Notably even all-seasons take almost double the braking distance compared to winter tires on packed snow. In reality there is no such thing as all-season tires. All-seasons are only three-season tires. If you need to drive on snowy or ice roads, you need winter tires. In fact, in Scandinavia one does not have all-seasons at all. In the summertime one has summer tires, i.e. the best and proper tires for summer conditions, and then on winter time one has winter tires (studded or not), i.e. the best and proper tires for winter conditions. All-seasons are just a compromise giving you mediocre or poor performance on all conditions. For more info, check out for example these reviews on e.g. Tirerack, Automobile magazine, Car & Driver, TiresByWeb, Canadian Tire, and EzineMark.com.
Surprisingly enough, the threshold for winter tires to overtake summer tires in performance is as high as 7 degrees Celsius (ca 46 Fahrenheit). At this temperature the rubber compounds in summer tires are getting hard enough so that the performance starts to decrease, whereas winter tires are still soft (and continue being soft to well below freezing temperatures) and start to perform better.
If you have winter tires (studded or non-studded) you should in general keep all possible electronic nannies turned on when driving. When the slippery spot hits you by surprise, you want all help possible. If you nevertheless know what you are doing and want to maximize the performance and traction on very slippery or snowy conditions, you should turn off the electronic traction control and possibly also ESC (electronic stability control). The reason is that in most modern cars these systems do not allow enough slippage for maximum winter tire traction. These systems are usually designed to simply remove slippage and slow down the vehicle to achieve that. On the other hand modern winter tires achieve maximum traction at 40-50% slippage levels. That is, if you spin your winter tires on snowy roads in a controlled fashion you are very likely to get better traction than with all the electronic systems on. For more information, check out this Tirerack video (particularly from 1:55 on)
Winter tires are made of softer rubber than all-season or summer tires. This enables them to have superior traction even on dry roads on below freezing conditions. On the other hand the softer rubber softens even more on warm days and thus the winter tires wear quicker. They are also a little bit noisier than all-season or summer tires. Driving winter tires in the middle of summer is a certain death sentence to the tires as they will wear out very quickly. In general winter tires are also ‘wobblier’ to drive so the handling and particularly cornering is not as good as with proper summer tires on warm days.
All-wheel drive systems help with acceleration in slippery conditions, so not getting winter tires might make sense to some people. The reality is that all-wheel systems do not help with braking at all (in fact all-wheel version of the same vehicle compared to front-wheel drive version has a longer stopping distance due to added weight). For proper braking and cornering, all-wheel vehicles need winter tires as much as the front- or rear-wheel drive vehicles.
Winter tires are a little but more expensive than all-season tires, but the cost difference (of higher tire cost and extra steel rims) becomes marginal if considered over the lifetime of the vehicle. That is, if one drives the vehicle for more than 100,000km, one is very likely to need two rounds of tires over that time. These two rounds can be two rounds of all-seasons, or one set of summer tires and one set of winter tires. The cost in the end will be roughly the same, but in the latter case one has had much better performing tires all year round for all those miles driven.
You can not go wrong buying Nokian Hakkapeliitta R, Michelin Latitude X-ice or Bridgestone Blizzak DM-V1 tires. The Nokian are most expensive and most difficult to find, but they also are the best no compromise severe weather condition winter tires out there. You should buy a little bit narrower tires than your summer tires (e.g. 235 winter vs 245 summer) as the narrower tire will cut through the snow easier increasing traction.