Harder rubber compounds get even harder in cold temperatures, so they lose their traction and ability to 'stick' to the pavement (which also hardens considerably in the cold). The magic number where winter tires grip better than all-seasons is, you guessed it, 7 degrees Celsius.
When temperatures begin to hit around 7 degrees Celsius is typically when the average all-season or your typical spring/summer tire begins to lose traction. Rubber for winter tires works best at 7 degrees or below because tires are made from a softer rubber compound than summers or even all-seasons.
In north and east Ontario, the rule of thumb is 7-for-7: wait until there are seven consistent days at 7 degrees Celsius. The reverse is also true for transitioning to winter. Ottawa's CAA Members can avoid the tire swap lineups at on-site vendors and save money with our economical new Mobile Tire Service.
50 percent worn – 7/32” REPLACE TIRES. 75 percent worn – 4.5/32” 100 percent worn – 2/32”
When the seasonal temperature falls below 7 °C (46 °F), it's time to switch to winter tires.
It is not recommended to drive on these types of tires at temperatures below 40 degrees F (5 degrees C). It is recommended these types of tires be stored indoors at temperatures maintained at above 20 degrees F (-7 degrees C) when not in use.
Rubber compounds on summer tires will also stiffen when temperatures drop below 40 degrees Fahrenheit, so even if there is no snow or ice, the tire will still lose traction. Winter weather may also cause your tires to lose their elasticity, making them crack.
The U.S. Department of Transportation recommends replacing tires when they reach 2/32”, and many states legally require tires to be replaced at this depth.
The tire tread depth gauge measures in 32nds of an inch. Good tire tread depth will be 6/32 or deeper. If the depth is 4/32, you should start thinking of replacing your tires and getting new ones. 2/32 or less means that you should change your tires ASAP.
Used tires tread can be up to 90%, but the average is 6-8/32”. Tires in good condition should have a minimum of 6/32” to be useful, or 4/32” if the tire is 13-14”. The average legal minimum tread depth is 2/32”, but driving becomes unsafe with such a tread.
This is colder than any weather temperature ever measured on Earth. And possibly colder than low Martian temperatures. It is not cold enough though to liquify oxygen or nitrogen.
The 10-degree rule, also called the Q 10 rule. In essence, the 10-degree rule says that for every 10°C increase, the reaction rates double. As a consequence, the useful life time of the material will be halved.
1°C is colder than 7°C.
All tyres (including spare tyres) more than ten years old should be removed from service and replaced with new tyres.
All-season rubber compounds stiffen as temperatures drop By the time they drop below 45 degrees, they start to lose traction which makes braking, acceleration and cornering less reliable and more difficult.
This is called hydroplaning. In a heavy rain, your tires can lose all traction with the road at about 50 mph. Bald or badly worn tires will lose traction at much lower speeds. The best way to keep from hydroplaning is to slow down in the rain or when the road is wet.
Most tyre manufacturers recommend replacing your tyres every 20,000 to 40,000 miles, or when your tread depth falls below 2mm.
A tire with a tread depth below 1.6 millimeters (2/32 inches) lacks grip. Braking distance and vehicle control are impaired. These tires are not safe for driving and must be replaced.
He says research carried out by Michelin shows that changing a tyre with 3mm or 4mm of tread remaining – instead of 1.6mm – equates on average to an extra tyre per company car every two years.
Some automakers suggest that tires be replaced as soon as they turn six years old. Some tire experts contend that tires can last anywhere from six to ten years if they're stored and cared for properly. We recommend replacing tires aged 6-10 years, no matter how much tread remains.
It's always best to replace all 4 tires at the same time. This is because all 4 tires spin independently of one another, and different tread depths and/or styles can cause them to spin at different speeds. That could potentially damage the drive train, and possibly affect an indirect TPMS system if the vehicle has one.
Placing the new tires on the rear axle helps maintain safer and more predictable handling. As you approach 70 percent worn or more, you should just replace all four tires. To maintain optimum and balanced handling, remember not to change the type of tire.
More air in your winter tires
For winter tires, you should inflate the tires to 3 PSI above the summer tire recommendation, since tire pressure decreases as much as 1 PSI with each 10-degree drop in temperature.
7 Degrees Celsius: The Break Point
When temperatures begin to hover around seven degrees Celsius, it's a good time to consider making the switch.
The short answer is “yes,” you can use summer tires in rain since this is one of their strongest features. The longer answer is that summer tires perform well on both dry and wet roads because they offer great braking and cornering, and move water away from the tire quickly to prevent hydroplanning.