Wednesday, December 7, 2011

Getting to know your tires

A basic fact about tire technology is, all- season tires loose grip as the temperature drops. An opposing fact is, winter tires increase their grip as the temperature plunges. These apposing facts about tire rubber are most effective around the 7 degree Celsius mark , as the rubber on all-season tires hardens and their grip loosens, winter tires stay soft and improve their grip. In fact, the colder it gets, the better grip they have.
When is it time to change to winter tires? Most of us wait until it snows before rushing into our dealerships to make the change. Winter tires show improvements over high performance and all-season tires on dry clean pavement, even at slightly above zero temperatures. This time of year a THUMP sound may come from your all-season tires when first driving off in the morning. This is caused as those all-season tires work out the flat spots on their bottoms, from being parked overnight. The THUMP sound is a message that the all-season rubber on your car is not pliable enough to grip the pavement as temperatures drop. This is the time to change to winter rubber. Another indicator would be around the 7 degree Celsius temperature.
In the past I was fortunate to work as an instructor at various performance driving schools. Some colleagues of mine performed tests in various conditions with a family sedan vehicle using winter, all-season and summer tires. These tests were conducted over several months in the fall and winter season, utilizing braking, cornering and slamon exercises. The data gathered was too extensive to list in this blog however in every exercise the finishing order was winter tires - >all season tires -> summer tires.
Here are some of the results from tests I’ve conducted: In February with the temperature at minus-14 C and no sun on the pavement, a panic stop from 80 km/h produced stopping distances of 49 meters for the summer tire, 39 meters for the all-season, and 34 meters for the Winter tire.
 To consider how well these tires can take evasive action on winter tarmac, a simple slalom with cones placed 10 steps apart and a sharp left turn at the end was set up.  Again the  Winter tire set the pace with a time of 21.3 seconds in February when it was cloudy and -14 C. The all-season came next at 22.1 seconds and the summer tire clocked in at 24.6 seconds.
Stopping distance spreads of 15 meters at minus-14 C can create a huge safety buffer for any driver, just by switching tires for the winter. Even at minus-6 C, the spread was 10.7 meters better for the winter versus the summer tire. Isn’t it time to switch over now?

Ian Phillips    
ian@maplenissan.com
   

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