Christmas is a busy driving season for a lot of drivers. Before setting off on a longer trip, the first thing you should check are your tyres. Using the correct equipment allows for safe mobility even in slippery and dark conditions. Drivers should make sure that their tyres are in good condition and have plenty of grip.
Winter tires need more air
Car tires will slowly let out air and require periodic refills. Inflation pressure requires special attention in winter. While cars have inflation pressure recommendations, they commonly lack a higher value that is recommended for winter tires.
“Temperature variations will alter tyre pressure. A temperature drop of 10 degrees will lower tyre pressure by approx. 0.1 bar. For this reason, I recommend that you inflate your tires 0.2 bar (20 kPa) above the vehicle’s recommended value in winter,” says Matti Morri, Technical Customer Service Manager for Nokian Tires.
Morri recommends checking the inflation pressure on cold tires, since tires that have been warmed up by driving will always have higher pressures. Correct inflation pressure has a major effect on the handling and tyre wear. Underinflated tires are also unsafe, as they will have longer braking distances and poorer handling and be generally more susceptible to damage. You should also check the inflation pressure of your spare tyre and keep it at a higher pressure than the tires you are using, since the inflation pressure tends to fall over time.
Tread depth indicates the condition of the tires
The rubber tires fitted on the different axles will wear down at different rates. However, you can even out the wear by rotating tires between the axles. Usually, switching the tyies from front to rear and vice versa once per season is sufficient. Not rotating your tires will most likely result in an unevenly worn tyre set, with some good tires and some unusable ones. You should never let the difference in tread depth exceed 2 mm between different axles.
“A tyre set that is in good condition and evenly worn will always provide the best handling. However, if one pair of tires is much more worn than the other, you should fit the better ones in the rear for safety. Tread depth and stud protrusion are good indicators in this respect. Providing the rear wheels with good grip on the road surface will help to prevent the most dangerous scenarios where the car loses grip and goes into a slide,” M. Morri explains.
You can track the wearing down of your tires by measuring the tread depth. The rule of thumb is four millimetres. Once the tread depth falls below this level and the tread pattern is clearly worn out, the tyre will start to lose grip. Bald tires are slippery. On slushy winter roads, for example, these tires may easily lift the car on top of the slush as the tyre has no time to displace the slush from between the road and the tyre. The same occurs during aquaplaning. The car becomes difficult to control and this increases the risk of running off the road.
“A good tyre with sufficient grip will obey the driver’s commands and even correct steering mistakes. Driving is easy when the tyre behaves logically and you can feel the grip limits”, Morri says.
You can easily measure tread depth at home by using a coin or a match. See here for a quick guide. In modern tires, you can see the remaining tread depth even without measuring it. For example, the Driving Safety Indicator (DSI) patented by Nokian Tires shows the remaining tread depth in millimetres at the centre of the tread. In addition to the row of numbers, the tyre may also have a snowflake symbol. Once it has worn out completely, you should replace your tires.
When loading your car with Christmas presents
When loading your car, you should place the heaviest loads at the bottom and tie down or support any loose items so that they will not fly during a sudden braking. More mass equals more force; therefore, when driving into corners or on slippery surfaces, you should bear in mind that a fully packed vehicle will take longer to stop than an empty one.
“Ensure that your windscreen washer fluid is frost-proof and remember to bring with you a reflective vest, flashlight and warm clothing in case you get stuck on the roads. Reserve sufficient time, take a snack with you, have breaks every now and then and keep up the holiday spirit. These are the best tools for Christmas traffic,” Morri summarises.
Quick checklist for your winter tires:
- Check tyre pressure every few weeks. Inflation pressure has a major effect on driving comfort and tyre wear. Keep the tyre pressure 0.2 bar higher in winter.
- Measure tread depth a couple of times per season. If the tread depth is below 4 millimetres, it is time to replace the tires.
- Rotate the tires between the axles. If the difference in tread depth is over 2 millimetres, you should switch the tires from one axle to another.
- Check the age of the tire. Tires last for approximately 6 years in active use. Once tires are 10 years old, they should no longer be used. The rubber compound hardens with age, thereby reducing grip.
This feature article was first published by Nokian Tires on December 20, 2017.