Key is that the higher the number, the greater load-carrying capacity. So keep the number the same or higher, because your tires are matched to the weight of your car. Never choose a tire with a lower load-carrying capacity than the original equipment tire size. The 300 is treadwear, which represents the tire s comparative wear when measured against the government-mandated tire which is rated at 100. So this tire wore three times longer than the control tire.
Traction indicates the level of grip the tire possesses.
Temperature rating deals with the tire s ability to disperse built-up heat. Heat causes rubber to deteriorate over time, so dispersing heat increases tire life. Each tire manufacturer determines UTQG ratings for their products. Realize that UTQGs are more accurate when comparing tires within the same line versus tires from two different makers. The speed-rating system in use today was developed in Europe to categorize tires developed for specific vehicle speed requirements.