Joined: Feb 2013
Posts: 1,472
Likes: 11
From: Near St. Louis, Missouri
Bikes: Giant Defy Advanced, Breezer Doppler Team, Schwinn Twinn Tandem, Windsor Tourist, 1954 JC Higgens
GP4000s have little holes in the tread in a few places. When these little holes are gone from wear, that means the tire is officially worn out. In practice you can get some more miles out of them.