Treadwear 

Treadwear grades are an indication of a tire's relative wear rate. The higher the treadwear number is, the longer it should take for the tread to wear down.

A control tire is assigned a grade of 100. Other tires are compared to the control tire. For example, a tire grade of 200 should wear twice as long as the control tire.

Of current tires:

• 15% are rated below 200
• 25% are rated 201 - 300
• 32% are rated 301 - 400
• 20% are rated 401 - 500
• 6% are rated 501 - 600
• 2% are rated above 600