|1. All-season tires have better wet-road grip than summer tires.|
In which season will an "all-season" tire offer better wet-road traction than a comparable "summer" tire? Answer: None.
Here's the truth: An all-season tire trades wet-road traction (among other things) for enhanced mobility in snow and in sub-freezing temperatures. Designing a tire is an exercise in compromises: Improving a certain tire performance, almost always means diminishing another—or several others. (Some more accurately use the term "three-season" when referring to summer tires.)
To make things even more complex, switch categories (or even brands) and the results may change: An ultra-high-performance all-season tire may offer better wet grip than a high-performance summer tire or, especially, a grand-touring summer tire.
2. Plenty of tread means plenty of remaining tire life.
Tires can reach the end of their lives without having gone far or done much work.
Some auto manufacturers recommend replacing tires every five or six years, regardless of tread depth. A tire that's been on a car seven or eight years is much like a 65-year-old human: No matter how fit and healthy he looks, he shouldn't play rugby against 19-year-olds, as a sharp impact or an aggressive maneuver could have unhappy results. If it's 105° outside, a simple stroll can be deadly to both out-of-shape older people and poorly maintained old tires.
Here's how you can tell how old your tire is: Look on its sidewall to find the letters "DOT." Following that will be a sequence of numbers, which may be in three or four separate windows. The last four numbers tell when the tire was made: "3106" means the tire was built during the 31st week of 2006. While you're on your knees, check for hairline cracks in the sidewall: That's a strong indication the tire needs replacing.
Deteriorating rubber is a big a problem for rarely driven vehicles, such as motor homes, collector cars, exotic cars, vehicles owned by senior citizens, and vans operated by charitable organizations. (A request: If you have older neighbors, check their tires for proper air pressure and signs of aging. And don't let them play rugby.)