What does treadwear rating mean?

What does treadwear rating mean?
The treadwear rating of a tire is a reflection of the expected lifespan of the tire. The higher the treadwear rating, the longer the tire should last.

This rating is based on comparison with a "Course Monitoring Tire" (CMT)with an assigned treadwear of "100." A tire with 300 treadwear should last three times longer than the CMT.

However, most manufacturers use this rating as a marketing technique. This means that many treadwear numbers are stated higher than "actual" to give an advantage over a competing tire/brand. Treadwear numbers, however, can usually be reliable when comparing different tire offerings from the same manufacturer.