Just purchased a used 2012 Subaru all wheel drive Forester. It came with a new set of Wild Peak AIT Trail tires 215/65 R16 on generic rims. Owner also provided Cooper 225/553 R17 Discoverer True North tires on original Subaru rims. Not sure why two sets of tires. Are the Coopers all weather or do I need to swap them out for the winter months. Also, confused about different sized rims. Obviously, I know nothing about tires and need advice. Thanks
From The Tire Rack:
The Discoverer True North is Cooper’s Studless Ice & Snow winter / snow tire developed for the drivers of coupes, sedans, crossovers and SUVs. Designed to provide exceptional traction in snowy, slushy and icy conditions along with responsive steering and confident handling, the Discoverer True North meets the tire industry’s severe snow service rating and earns the three-peak mountain snowflake (3PMSF) symbol.
The specialized, winter-focused compound of the Discoverer True North boasts the highest silica content of any Cooper winter tire. Wide tread blocks in the outboard shoulder improve lateral grip for dry handling traction, while the higher void ratio of the middle of the tread and inboard shoulder aids wet performance. The circumferential center groove and wide lateral notches evacuate water and slush to improve hydroplaning resistance, and the specialized winter compound combined with the high sipe density provides traction on wet surfaces, in light or deep snow and on ice.
The internal construction of the Discoverer True North consists of a two-ply polyester casing that helps balance the relationship between durability and ride comfort. Two wide, steel belts support the tread area, and a single-ply, nylon reinforcement aids handling response and provides high-speed capability.
Due to the traction capabilities of the Discoverer True North, Cooper Tire recommends using Discoverer True North tires only in sets of four to provide the best handling characteristics and tire performance.
Sounds like just recommended for winter weather.
Good winter tires are not great for summer, and vice versa. Some people go for a compromise ‘all-season’ tire, which is not best in either summer or winter, but you don’t have to change them twice per year. Other people change back and forth to get better traction in winter and summer. If you’re going to change back and forth, having an extra set of rims means you can change them in your driveway if you want to. If you don’t have an extra set of rims, you have to take the extra set of tires to a tire shop and have the shop mount and balance the other tires. If I were going to use different winter tires, I’d buy an extra set of rims.
Since you already have winter tires, I’d just switch to those about the time you expect the first snow in your area. Then swap back in the spring. Once the winter tires are worn out, you can decide whether it’s worth continuing to do the semiannual tire swap. Unless you live in a place with particularly awful winters, I’d probably just use decent all-season tires on that car and make sure they have plenty of tread before winter.
The different rim size isn’t a problem. You can use different rim sizes on the vehicle (it might even have had different rim sizes as factory options).
Winter tires have rubber compounds that stay softer in cold weather so the tread has a better grip on the road. If you run them in warm weather the rubber gets too soft and will wear excessively.
The reverse is true for tires designed for summer driving, the rubber compounds for those typically hold up well in hot conditions but get hard in frigid conditions and that makes for a slippery ride. The wide sipes and aggressive tread patterns will help on snow, but on ice all bets are off unless you have studded tires. Some manufacturers used walnut shells in the tread rubber for a while but the results were only so-so. I don’t know if those are still available.
When I lived in south-central Alaska most people switched to studded winter tires from October to March.
Thanks to everyone who responded. This was extremely helpful.